path: root/Samples/CommonSrc/Render/Render_GL_Device.cpp

/************************************************************************************

Filename    :   Render_GL_Device.cpp
Content     :   RenderDevice implementation for OpenGL
Created     :   September 10, 2012
Authors     :   Andrew Reisse

Copyright   :   Copyright 2012 Oculus VR, LLC All Rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

************************************************************************************/

#include "../Render/Render_GL_Device.h"
#include "Kernel/OVR_Log.h"
#include "OVR_CAPI_GL.h"

namespace OVR { namespace Render { namespace GL {


#if !defined(OVR_OS_MAC)

// GL Hooks for PC.
#if defined(OVR_OS_WIN32)
    
PFNWGLCHOOSEPIXELFORMATARBPROC           wglChoosePixelFormatARB;
PFNWGLCREATECONTEXTATTRIBSARBPROC        wglCreateContextAttribsARB;
PFNWGLGETSWAPINTERVALEXTPROC             wglGetSwapIntervalEXT;
PFNWGLSWAPINTERVALEXTPROC                wglSwapIntervalEXT;
    
void* GetFunction(const char* functionName)
{
    return wglGetProcAddress(functionName);
}

#else

PFNGLXSWAPINTERVALEXTPROC                glXSwapIntervalEXT;

void (*GetFunction(const char *functionName))( void )
{
    return glXGetProcAddress((GLubyte*)functionName);
}

#endif

PFNGLGETSTRINGIPROC                      glGetStringi;
PFNGLGENFRAMEBUFFERSPROC                 glGenFramebuffers;
PFNGLDELETEFRAMEBUFFERSPROC              glDeleteFramebuffers;
PFNGLDELETESHADERPROC                    glDeleteShader;
PFNGLCHECKFRAMEBUFFERSTATUSPROC          glCheckFramebufferStatus;
PFNGLFRAMEBUFFERRENDERBUFFERPROC         glFramebufferRenderbuffer;
PFNGLFRAMEBUFFERTEXTURE2DPROC            glFramebufferTexture2D;
PFNGLBINDFRAMEBUFFERPROC                 glBindFramebuffer;
PFNGLACTIVETEXTUREPROC                   glActiveTexture;
PFNGLDISABLEVERTEXATTRIBARRAYPROC        glDisableVertexAttribArray;
PFNGLVERTEXATTRIBPOINTERPROC             glVertexAttribPointer;
PFNGLENABLEVERTEXATTRIBARRAYPROC         glEnableVertexAttribArray;
PFNGLBINDBUFFERPROC                      glBindBuffer;
PFNGLUNIFORMMATRIX3FVPROC                glUniformMatrix3fv;
PFNGLUNIFORMMATRIX4FVPROC                glUniformMatrix4fv;
PFNGLDELETEBUFFERSPROC                   glDeleteBuffers;
PFNGLBUFFERDATAPROC                      glBufferData;
PFNGLGENBUFFERSPROC                      glGenBuffers;
PFNGLMAPBUFFERPROC                       glMapBuffer;
PFNGLUNMAPBUFFERPROC                     glUnmapBuffer;
PFNGLGETSHADERINFOLOGPROC                glGetShaderInfoLog;
PFNGLGETSHADERIVPROC                     glGetShaderiv;
PFNGLCOMPILESHADERPROC                   glCompileShader;
PFNGLSHADERSOURCEPROC                    glShaderSource;
PFNGLCREATESHADERPROC                    glCreateShader;
PFNGLCREATEPROGRAMPROC                   glCreateProgram;
PFNGLATTACHSHADERPROC                    glAttachShader;
PFNGLDETACHSHADERPROC                    glDetachShader;
PFNGLDELETEPROGRAMPROC                   glDeleteProgram;
PFNGLUNIFORM1IPROC                       glUniform1i;
PFNGLGETUNIFORMLOCATIONPROC              glGetUniformLocation;
PFNGLGETACTIVEUNIFORMPROC                glGetActiveUniform;
PFNGLUSEPROGRAMPROC                      glUseProgram;
PFNGLGETPROGRAMINFOLOGPROC               glGetProgramInfoLog;
PFNGLGETPROGRAMIVPROC                    glGetProgramiv;
PFNGLLINKPROGRAMPROC                     glLinkProgram;
PFNGLBINDATTRIBLOCATIONPROC              glBindAttribLocation;
PFNGLUNIFORM4FVPROC                      glUniform4fv;
PFNGLUNIFORM3FVPROC                      glUniform3fv;
PFNGLUNIFORM2FVPROC                      glUniform2fv;
PFNGLUNIFORM1FVPROC                      glUniform1fv;
PFNGLCOMPRESSEDTEXIMAGE2DPROC            glCompressedTexImage2D;
PFNGLTEXIMAGE2DMULTISAMPLEPROC           glTexImage2DMultisample;
PFNGLRENDERBUFFERSTORAGEPROC             glRenderbufferStorage;
PFNGLBINDRENDERBUFFERPROC                glBindRenderbuffer;
PFNGLGENRENDERBUFFERSPROC                glGenRenderbuffers;
PFNGLDELETERENDERBUFFERSPROC             glDeleteRenderbuffers;
PFNGLGENVERTEXARRAYSPROC                 glGenVertexArrays;
PFNGLDELETEVERTEXARRAYSPROC              glDeleteVertexArrays;
PFNGLBINDVERTEXARRAYPROC                 glBindVertexArray;
PFNGLBLITFRAMEBUFFEREXTPROC              glBlitFramebuffer;

void InitGLExtensions()
{
    if (glGenFramebuffers)
        return;

#if defined(OVR_OS_WIN32)
    wglGetSwapIntervalEXT =             (PFNWGLGETSWAPINTERVALEXTPROC)             GetFunction("wglGetSwapIntervalEXT");
    wglSwapIntervalEXT =                (PFNWGLSWAPINTERVALEXTPROC)                GetFunction("wglSwapIntervalEXT");
#else
    glXSwapIntervalEXT =                (PFNGLXSWAPINTERVALEXTPROC)                GetFunction("glXSwapIntervalEXT");
#endif

    glGetStringi =                      (PFNGLGETSTRINGIPROC)                      GetFunction("glGetStringi");
    glGenFramebuffers =                 (PFNGLGENFRAMEBUFFERSPROC)                 GetFunction("glGenFramebuffersEXT");
    glDeleteFramebuffers =              (PFNGLDELETEFRAMEBUFFERSPROC)              GetFunction("glDeleteFramebuffersEXT");
    glDeleteShader =                    (PFNGLDELETESHADERPROC)                    GetFunction("glDeleteShader");
    glCheckFramebufferStatus =          (PFNGLCHECKFRAMEBUFFERSTATUSPROC)          GetFunction("glCheckFramebufferStatusEXT");
    glFramebufferRenderbuffer =         (PFNGLFRAMEBUFFERRENDERBUFFERPROC)         GetFunction("glFramebufferRenderbufferEXT");
    glFramebufferTexture2D =            (PFNGLFRAMEBUFFERTEXTURE2DPROC)            GetFunction("glFramebufferTexture2DEXT");
    glBindFramebuffer =                 (PFNGLBINDFRAMEBUFFERPROC)                 GetFunction("glBindFramebufferEXT");
    glActiveTexture =                   (PFNGLACTIVETEXTUREPROC)                   GetFunction("glActiveTexture");
    glDisableVertexAttribArray =        (PFNGLDISABLEVERTEXATTRIBARRAYPROC)        GetFunction("glDisableVertexAttribArray");
    glVertexAttribPointer =             (PFNGLVERTEXATTRIBPOINTERPROC)             GetFunction("glVertexAttribPointer");
    glEnableVertexAttribArray =         (PFNGLENABLEVERTEXATTRIBARRAYPROC)         GetFunction("glEnableVertexAttribArray");
    glBindBuffer =                      (PFNGLBINDBUFFERPROC)                      GetFunction("glBindBuffer");
    glUniformMatrix3fv =                (PFNGLUNIFORMMATRIX3FVPROC)                GetFunction("glUniformMatrix3fv");
    glUniformMatrix4fv =                (PFNGLUNIFORMMATRIX4FVPROC)                GetFunction("glUniformMatrix4fv");
    glDeleteBuffers =                   (PFNGLDELETEBUFFERSPROC)                   GetFunction("glDeleteBuffers");
    glBufferData =                      (PFNGLBUFFERDATAPROC)                      GetFunction("glBufferData");
    glGenBuffers =                      (PFNGLGENBUFFERSPROC)                      GetFunction("glGenBuffers");
    glMapBuffer =                       (PFNGLMAPBUFFERPROC)                       GetFunction("glMapBuffer");
    glUnmapBuffer =                     (PFNGLUNMAPBUFFERPROC)                     GetFunction("glUnmapBuffer");
    glGetShaderInfoLog =                (PFNGLGETSHADERINFOLOGPROC)                GetFunction("glGetShaderInfoLog");
    glGetShaderiv =                     (PFNGLGETSHADERIVPROC)                     GetFunction("glGetShaderiv");
    glCompileShader =                   (PFNGLCOMPILESHADERPROC)                   GetFunction("glCompileShader");
    glShaderSource =                    (PFNGLSHADERSOURCEPROC)                    GetFunction("glShaderSource");
    glCreateShader =                    (PFNGLCREATESHADERPROC)                    GetFunction("glCreateShader");
    glCreateProgram =                   (PFNGLCREATEPROGRAMPROC)                   GetFunction("glCreateProgram");
    glAttachShader =                    (PFNGLATTACHSHADERPROC)                    GetFunction("glAttachShader");
    glDetachShader =                    (PFNGLDETACHSHADERPROC)                    GetFunction("glDetachShader");
    glDeleteProgram =                   (PFNGLDELETEPROGRAMPROC)                   GetFunction("glDeleteProgram");
    glUniform1i =                       (PFNGLUNIFORM1IPROC)                       GetFunction("glUniform1i");
    glGetUniformLocation =              (PFNGLGETUNIFORMLOCATIONPROC)              GetFunction("glGetUniformLocation");
    glGetActiveUniform =                (PFNGLGETACTIVEUNIFORMPROC)                GetFunction("glGetActiveUniform");
    glUseProgram =                      (PFNGLUSEPROGRAMPROC)                      GetFunction("glUseProgram");
    glGetProgramInfoLog =               (PFNGLGETPROGRAMINFOLOGPROC)               GetFunction("glGetProgramInfoLog");
    glGetProgramiv =                    (PFNGLGETPROGRAMIVPROC)                    GetFunction("glGetProgramiv");
    glLinkProgram =                     (PFNGLLINKPROGRAMPROC)                     GetFunction("glLinkProgram");
    glBindAttribLocation =              (PFNGLBINDATTRIBLOCATIONPROC)              GetFunction("glBindAttribLocation");
    glUniform4fv =                      (PFNGLUNIFORM4FVPROC)                      GetFunction("glUniform4fv");
    glUniform3fv =                      (PFNGLUNIFORM3FVPROC)                      GetFunction("glUniform3fv");
    glUniform2fv =                      (PFNGLUNIFORM2FVPROC)                      GetFunction("glUniform2fv");
    glUniform1fv =                      (PFNGLUNIFORM1FVPROC)                      GetFunction("glUniform1fv");
    glCompressedTexImage2D =            (PFNGLCOMPRESSEDTEXIMAGE2DPROC)            GetFunction("glCompressedTexImage2D");
    glTexImage2DMultisample =           (PFNGLTEXIMAGE2DMULTISAMPLEPROC)           GetFunction("glTexImage2DMultisample");
    glRenderbufferStorage =             (PFNGLRENDERBUFFERSTORAGEPROC)             GetFunction("glRenderbufferStorageEXT");
    glBindRenderbuffer =                (PFNGLBINDRENDERBUFFERPROC)                GetFunction("glBindRenderbufferEXT");
    glGenRenderbuffers =                (PFNGLGENRENDERBUFFERSPROC)                GetFunction("glGenRenderbuffersEXT");
    glDeleteRenderbuffers =             (PFNGLDELETERENDERBUFFERSPROC)             GetFunction("glDeleteRenderbuffersEXT");
    glGenVertexArrays =                 (PFNGLGENVERTEXARRAYSPROC)                 GetFunction("glGenVertexArrays");
    glDeleteVertexArrays =              (PFNGLDELETEVERTEXARRAYSPROC)              GetFunction("glDeleteVertexArrays");
    glBindVertexArray =                 (PFNGLBINDVERTEXARRAYPROC)                 GetFunction("glBindVertexArray");
    glBlitFramebuffer =                 (PFNGLBLITFRAMEBUFFEREXTPROC)              GetFunction("glBlitFramebufferEXT");
}

#endif

static const char* StdVertexShaderSrc =
"#version 110\n"

    "uniform mat4 Proj;\n"
    "uniform mat4 View;\n"
    
    "attribute vec4 Position;\n"
    "attribute vec4 Color;\n"
    "attribute vec2 TexCoord;\n"
    "attribute vec2 TexCoord1;\n"
    "attribute vec3 Normal;\n"
    
    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord;\n"
    "varying vec2 oTexCoord1;\n"
    "varying vec3 oNormal;\n"
    "varying vec3 oVPos;\n"
    
    "void main()\n"
    "{\n"
    "   gl_Position = Proj * (View * Position);\n"
    "   oNormal = vec3(View * vec4(Normal,0));\n"
    "   oVPos = vec3(View * Position);\n"
    "   oTexCoord = TexCoord;\n"
    "   oTexCoord1 = TexCoord1;\n"
    "   oColor = Color;\n"
    "}\n";

static const char* DirectVertexShaderSrc =
    "#version 110\n"
    
    "uniform mat4 View;\n"
    
    "attribute vec4 Position;\n"
    "attribute vec4 Color;\n"
    "attribute vec2 TexCoord;\n"
    "attribute vec3 Normal;\n"
    
    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord;\n"
    "varying vec3 oNormal;\n"
    
    "void main()\n"
    "{\n"
    "   gl_Position = View * Position;\n"
    "   oTexCoord = TexCoord;\n"
    "   oColor = Color;\n"
    "   oNormal = vec3(View * vec4(Normal,0));\n"
    "}\n";

static const char* SolidFragShaderSrc =
    "#version 110\n"
    
    "uniform vec4 Color;\n"
    
    "void main()\n"
    "{\n"
    "   gl_FragColor = Color;\n"
    "}\n";

static const char* GouraudFragShaderSrc =
    "#version 110\n"
    
    "varying vec4 oColor;\n"
    
    "void main()\n"
    "{\n"
    "   gl_FragColor = oColor;\n"
    "}\n";

static const char* TextureFragShaderSrc =
    "#version 110\n"
    
    "uniform sampler2D Texture0;\n"
    
    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord;\n"
    
    "void main()\n"
    "{\n"
    "   gl_FragColor = oColor * texture2D(Texture0, oTexCoord);\n"
    "   if (gl_FragColor.a < 0.4)\n"
    "       discard;\n"
    "}\n";

#define LIGHTING_COMMON                                                          \
    "#version 110\n"                                                    \
    "uniform   vec3 Ambient;\n"                                                   \
    "uniform   vec4 LightPos[8];\n"                                                \
    "uniform   vec4 LightColor[8];\n"                                               \
    "uniform   float LightCount;\n"                                                  \
    "varying   vec4 oColor;\n"                                                  \
    "varying   vec2 oTexCoord;\n"                                               \
    "varying   vec3 oNormal;\n"                                                 \
    "varying   vec3 oVPos;\n"                                                   \
    "vec4 DoLight()\n"                                                                    \
    "{\n"                                                                                  \
    "   vec3 norm = normalize(oNormal);\n"                                                  \
    "   vec3 light = Ambient;\n"                                                             \
    "   for (int i = 0; i < int(LightCount); i++)\n"                                          \
    "   {\n"                                                                                   \
    "       vec3 ltp = (LightPos[i].xyz - oVPos);\n"                                            \
    "       float  ldist = length(ltp);\n"                                                       \
    "       ltp = normalize(ltp);\n"                                                              \
    "       light += clamp(LightColor[i].rgb * oColor.rgb * (dot(norm, ltp) / ldist), 0.0,1.0);\n" \
    "   }\n"                                                                                        \
    "   return vec4(light, oColor.a);\n"                                                             \
    "}\n"

static const char* LitSolidFragShaderSrc =
    LIGHTING_COMMON
    
    "void main()\n"
    "{\n"
    "   gl_FragColor = DoLight() * oColor;\n"
    "}\n";

static const char* LitTextureFragShaderSrc =
    LIGHTING_COMMON
    
    "uniform sampler2D Texture0;\n"
    
    "void main()\n"
    "{\n"
    "   gl_FragColor = DoLight() * texture2D(Texture0, oTexCoord);\n"
    "}\n";

static const char* AlphaTextureFragShaderSrc =
    "#version 110\n"
    
    "uniform sampler2D Texture0;\n"
    
    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord;\n"
    
    "void main()\n"
    "{\n"
    "   gl_FragColor = oColor * vec4(1,1,1,texture2D(Texture0, oTexCoord).r);\n"
    "}\n";

static const char* AlphaBlendedTextureFragShaderSrc =
    "#version 110\n"

    "uniform sampler2D Texture0;\n"

    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord;\n"
    
    "void main()\n"
    "{\n"
    "   vec4 finalColor = oColor;\n"
    "   finalColor *= texture2D(Texture0, oTexCoord);\n"
    // Blend state expects premultiplied alpha
    "   finalColor.rgb *= finalColor.a;\n"
    "   gl_FragColor = finalColor;\n"
    "}\n";

static const char* MultiTextureFragShaderSrc =
    "#version 110\n"
    
    "uniform sampler2D Texture0;\n"
    "uniform sampler2D Texture1;\n"
    
    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord;\n"
    "varying vec2 oTexCoord1;\n"
    
    "void main()\n"
    "{\n"
    "    vec4 color = texture2D(Texture0, oTexCoord);\n"
    
    "    gl_FragColor = texture2D(Texture1, oTexCoord1);\n"
    "    gl_FragColor.rgb = gl_FragColor.rgb * mix(1.9, 1.2, clamp(length(gl_FragColor.rgb),0.0,1.0));\n"
    
    "    gl_FragColor = color * gl_FragColor;\n"
    
    "   if (gl_FragColor.a <= 0.6)\n"
    "        discard;\n"
    "}\n";

static const char* PostProcessMeshFragShaderSrc =
    "#version 110\n"
    
    "uniform sampler2D Texture;\n"
    
    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord0;\n"
    "varying vec2 oTexCoord1;\n"
    "varying vec2 oTexCoord2;\n"
    
    "void main()\n"
    "{\n"
    "   gl_FragColor.r = oColor.r * texture2D(Texture, oTexCoord0).r;\n"
    "   gl_FragColor.g = oColor.g * texture2D(Texture, oTexCoord1).g;\n"
    "   gl_FragColor.b = oColor.b * texture2D(Texture, oTexCoord2).b;\n"
    "   gl_FragColor.a = 1.0;\n"
    "}\n";

static const char* PostProcessMeshTimewarpFragShaderSrc = PostProcessMeshFragShaderSrc;
static const char* PostProcessMeshPositionalTimewarpFragShaderSrc = PostProcessMeshFragShaderSrc;
static const char* PostProcessHeightmapTimewarpFragShaderSrc = PostProcessMeshFragShaderSrc;

static const char* PostProcessVertexShaderSrc =
    "#version 110\n"
    
    "uniform mat4 View;\n"
    "uniform mat4 Texm;\n"
    
    "attribute vec4 Position;\n"
    "attribute vec2 TexCoord;\n"
    
    "varying vec2 oTexCoord;\n"
    
    "void main()\n"
    "{\n"
    "   gl_Position = View * Position;\n"
    "   oTexCoord = vec2(Texm * vec4(TexCoord,0,1));\n"
    "}\n";

static const char* PostProcessMeshVertexShaderSrc =
    "#version 110\n"
    
    "uniform vec2 EyeToSourceUVScale;\n"
    "uniform vec2 EyeToSourceUVOffset;\n"

    "attribute vec2 Position;\n"
    "attribute vec4 Color;\n"
    "attribute vec2 TexCoord0;\n"
    "attribute vec2 TexCoord1;\n"
    "attribute vec2 TexCoord2;\n"

    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord0;\n"
    "varying vec2 oTexCoord1;\n"
    "varying vec2 oTexCoord2;\n"

    "void main()\n"
    "{\n"
    "   gl_Position.x = Position.x;\n"
    "   gl_Position.y = Position.y;\n"
    "   gl_Position.z = 0.5;\n"
    "   gl_Position.w = 1.0;\n"
    // Vertex inputs are in TanEyeAngle space for the R,G,B channels (i.e. after chromatic aberration and distortion).
    // Scale them into the correct [0-1],[0-1] UV lookup space (depending on eye)
    "   oTexCoord0 = TexCoord0 * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   oTexCoord0.y = 1.0-oTexCoord0.y;\n"
    "   oTexCoord1 = TexCoord1 * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   oTexCoord1.y = 1.0-oTexCoord1.y;\n"
    "   oTexCoord2 = TexCoord2 * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   oTexCoord2.y = 1.0-oTexCoord2.y;\n"
    "   oColor = Color;\n"              // Used for vignette fade.
    "}\n";

static const char* PostProcessMeshTimewarpVertexShaderSrc =
    "#version 110\n"
    
    "uniform vec2 EyeToSourceUVScale;\n"
    "uniform vec2 EyeToSourceUVOffset;\n"
    "uniform mat4 EyeRotationStart;\n"
    "uniform mat4 EyeRotationEnd;\n"

    "attribute vec2 Position;\n"
    "attribute vec4 Color;\n"
    "attribute vec2 TexCoord0;\n"
    "attribute vec2 TexCoord1;\n"
    "attribute vec2 TexCoord2;\n"

    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord0;\n"
    "varying vec2 oTexCoord1;\n"
    "varying vec2 oTexCoord2;\n"

    "void main()\n"
    "{\n"
    "   gl_Position.x = Position.x;\n"
    "   gl_Position.y = Position.y;\n"
    "   gl_Position.z = 0.0;\n"
    "   gl_Position.w = 1.0;\n"

    // Vertex inputs are in TanEyeAngle space for the R,G,B channels (i.e. after chromatic aberration and distortion).
    // These are now "real world" vectors in direction (x,y,1) relative to the eye of the HMD.
    "   vec3 TanEyeAngleR = vec3 ( TexCoord0.x, TexCoord0.y, 1.0 );\n"
    "   vec3 TanEyeAngleG = vec3 ( TexCoord1.x, TexCoord1.y, 1.0 );\n"
    "   vec3 TanEyeAngleB = vec3 ( TexCoord2.x, TexCoord2.y, 1.0 );\n"

    // Accurate time warp lerp vs. faster
#if 0
    // Apply the two 3x3 timewarp rotations to these vectors.
    "   vec3 TransformedRStart = (EyeRotationStart * vec4(TanEyeAngleR, 0)).xyz;\n"
    "   vec3 TransformedGStart = (EyeRotationStart * vec4(TanEyeAngleG, 0)).xyz;\n"
    "   vec3 TransformedBStart = (EyeRotationStart * vec4(TanEyeAngleB, 0)).xyz;\n"
    "   vec3 TransformedREnd   = (EyeRotationEnd * vec4(TanEyeAngleR, 0)).xyz;\n"
    "   vec3 TransformedGEnd   = (EyeRotationEnd * vec4(TanEyeAngleG, 0)).xyz;\n"
    "   vec3 TransformedBEnd   = (EyeRotationEnd * vec4(TanEyeAngleB, 0)).xyz;\n"
    // And blend between them.
    "   vec3 TransformedR = mix ( TransformedRStart, TransformedREnd, Color.a );\n"
    "   vec3 TransformedG = mix ( TransformedGStart, TransformedGEnd, Color.a );\n"
    "   vec3 TransformedB = mix ( TransformedBStart, TransformedBEnd, Color.a );\n"
#else
    "   mat3 EyeRotation;\n"
    "   EyeRotation[0] = mix ( EyeRotationStart[0], EyeRotationEnd[0], Color.a ).xyz;\n"
    "   EyeRotation[1] = mix ( EyeRotationStart[1], EyeRotationEnd[1], Color.a ).xyz;\n"
    "   EyeRotation[2] = mix ( EyeRotationStart[2], EyeRotationEnd[2], Color.a ).xyz;\n"
    "   vec3 TransformedR   = EyeRotation * TanEyeAngleR;\n"
    "   vec3 TransformedG   = EyeRotation * TanEyeAngleG;\n"
    "   vec3 TransformedB   = EyeRotation * TanEyeAngleB;\n"
#endif

    // Project them back onto the Z=1 plane of the rendered images.
    "   float RecipZR = 1.0 / TransformedR.z;\n"
    "   float RecipZG = 1.0 / TransformedG.z;\n"
    "   float RecipZB = 1.0 / TransformedB.z;\n"
    "   vec2 FlattenedR = vec2 ( TransformedR.x * RecipZR, TransformedR.y * RecipZR );\n"
    "   vec2 FlattenedG = vec2 ( TransformedG.x * RecipZG, TransformedG.y * RecipZG );\n"
    "   vec2 FlattenedB = vec2 ( TransformedB.x * RecipZB, TransformedB.y * RecipZB );\n"

    // These are now still in TanEyeAngle space.
    // Scale them into the correct [0-1],[0-1] UV lookup space (depending on eye)
    "   vec2 SrcCoordR = FlattenedR * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   vec2 SrcCoordG = FlattenedG * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   vec2 SrcCoordB = FlattenedB * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   oTexCoord0 = SrcCoordR;\n"
    "   oTexCoord0.y = 1.0-oTexCoord0.y;\n"
    "   oTexCoord1 = SrcCoordG;\n"
    "   oTexCoord1.y = 1.0-oTexCoord1.y;\n"
    "   oTexCoord2 = SrcCoordB;\n"
    "   oTexCoord2.y = 1.0-oTexCoord2.y;\n"
    "   oColor = vec4(Color.r, Color.r, Color.r, Color.r);\n"              // Used for vignette fade.
    "}\n";

static const char* PostProcessMeshPositionalTimewarpVertexShaderSrc =
#if 1 //TODO: Disabled until we fix positional timewarp and layering on GL.
PostProcessMeshTimewarpVertexShaderSrc;
#else
    "#version 150\n"

    "uniform sampler2D Texture0;\n"
    "uniform vec2 EyeToSourceUVScale;\n"
    "uniform vec2 EyeToSourceUVOffset;\n"
    "uniform vec2 DepthProjector;\n"
    "uniform vec2 DepthDimSize;\n"
    "uniform mat4 EyeRotationStart;\n"
    "uniform mat4 EyeRotationEnd;\n"

    "attribute vec2 Position;\n"
    "attribute vec4 Color;\n"
    "attribute vec2 TexCoord0;\n"
    "attribute vec2 TexCoord1;\n"
    "attribute vec2 TexCoord2;\n"

    "varying vec4 oColor;\n"
    "varying vec2 oTexCoord0;\n"
    "varying vec2 oTexCoord1;\n"
    "varying vec2 oTexCoord2;\n"

    "vec4 PositionFromDepth(vec2 inTexCoord)\n"
    "{\n"
    "   vec2 eyeToSourceTexCoord = inTexCoord * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   eyeToSourceTexCoord.y = 1.0 - eyeToSourceTexCoord.y;\n"
    "   float depth = texelFetch(Texture0, ivec2(eyeToSourceTexCoord * DepthDimSize), 0).x;\n" //FIXME: Use Texture2DLod for #version 110 support.
    "   float linearDepth = DepthProjector.y / (depth - DepthProjector.x);\n"
    "   vec4 retVal = vec4(inTexCoord, 1, 1);\n"
    "   retVal.xyz *= linearDepth;\n"
    "   return retVal;\n"
    "}\n"

    "vec2 TimewarpTexCoordToWarpedPos(vec2 inTexCoord, float a)\n"
    "{\n"
    // Vertex inputs are in TanEyeAngle space for the R,G,B channels (i.e. after chromatic aberration and distortion).
    // These are now "real world" vectors in direction (x,y,1) relative to the eye of the HMD.
    // Apply the 4x4 timewarp rotation to these vectors.
    "   vec4 inputPos = PositionFromDepth(inTexCoord);\n"
    "   vec3 transformed = mix ( EyeRotationStart * inputPos,  EyeRotationEnd * inputPos, a ).xyz;\n"
    // Project them back onto the Z=1 plane of the rendered images.
    "   vec2 flattened = transformed.xy / transformed.z;\n"
    // Scale them into ([0,0.5],[0,1]) or ([0.5,0],[0,1]) UV lookup space (depending on eye)
    "   vec2 noDepthUV = flattened * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    //"   float depth = texture2D(Texture0, noDepthUV).r;\n"
    "   return noDepthUV.xy;\n"
    "}\n"

    "void main()\n"
    "{\n"
    "   gl_Position.x = Position.x;\n"
    "   gl_Position.y = Position.y;\n"
    "   gl_Position.z = 0.0;\n"
    "   gl_Position.w = 1.0;\n"

    // warped positions are a bit more involved, hence a separate function
    "   oTexCoord0 = TimewarpTexCoordToWarpedPos(TexCoord0, Color.a);\n"
    "   oTexCoord0.y = 1.0 - oTexCoord0.y;\n"
    "   oTexCoord1 = TimewarpTexCoordToWarpedPos(TexCoord1, Color.a);\n"
    "   oTexCoord1.y = 1.0 - oTexCoord1.y;\n"
    "   oTexCoord2 = TimewarpTexCoordToWarpedPos(TexCoord2, Color.a);\n"
    "   oTexCoord2.y = 1.0 - oTexCoord2.y;\n"

    "   oColor = vec4(Color.r, Color.r, Color.r, Color.r);  // Used for vignette fade.\n"
    "}\n";
#endif


static const char* PostProcessHeightmapTimewarpVertexShaderSrc =
#if 1 //TODO: Disabled until we fix positional timewarp and layering on GL.
PostProcessMeshTimewarpVertexShaderSrc;
#else
    "#version 150\n"

    "uniform sampler2D Texture0;\n"
    "uniform vec2 EyeToSourceUVScale;\n"
    "uniform vec2 EyeToSourceUVOffset;\n"
    "uniform vec2 DepthDimSize;\n"
    "uniform mat4 EyeXformStart;\n"
    "uniform mat4 EyeXformEnd;\n"
    //"uniform mat4 Projection;\n"
    "uniform mat4 InvProjection;\n"

    "attribute vec2 Position;\n"
    "attribute vec3 TexCoord0;\n"

    "varying vec2 oTexCoord0;\n"

    "vec4 PositionFromDepth(vec2 position, vec2 inTexCoord)\n"
    "{\n"
    "   float depth = texelFetch(Texture0, ivec2(inTexCoord * DepthDimSize), 0).x;\n" //FIXME: Use Texture2DLod for #version 110 support.
    "   vec4 retVal = vec4(position, depth, 1);\n"
    "   return retVal;\n"
    "}\n"

    "vec4 TimewarpPos(vec2 position, vec2 inTexCoord, mat4 rotMat)\n"
    "{\n"
    // Apply the 4x4 timewarp rotation to these vectors.
    "   vec4 transformed = PositionFromDepth(position, inTexCoord);\n"
    "   transformed = InvProjection * transformed;\n"
    "   transformed = rotMat * transformed;\n"
    //"   transformed = mul ( Projection, transformed );\n"
    "   return transformed;\n"
    "}\n"

    "void main()\n"
    "{\n"
    "   vec2 eyeToSrcTexCoord = TexCoord0.xy * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "   oTexCoord0 = eyeToSrcTexCoord;\n"

    "   float timewarpLerpFactor = TexCoord0.z;\n"
    "   mat4 lerpedEyeRot;  // GL cannot mix() matrices :-( \n"
    "   lerpedEyeRot[0] = mix(EyeXformStart[0], EyeXformEnd[0], timewarpLerpFactor);\n"
    "   lerpedEyeRot[1] = mix(EyeXformStart[1], EyeXformEnd[1], timewarpLerpFactor);\n"
    "   lerpedEyeRot[2] = mix(EyeXformStart[2], EyeXformEnd[2], timewarpLerpFactor);\n"
    "   lerpedEyeRot[3] = mix(EyeXformStart[3], EyeXformEnd[3], timewarpLerpFactor);\n"
    //"    float4x4 lerpedEyeRot = EyeXformStart;\n"

    // warped positions are a bit more involved, hence a separate function
    "   gl_Position = TimewarpPos(Position.xy, oTexCoord0, lerpedEyeRot);\n"
    "}\n";
#endif
    
// Shader with lens distortion and chromatic aberration correction.
static const char* PostProcessFragShaderWithChromAbSrc =
    "#version 110\n"
    
    "uniform sampler2D Texture;\n"
    "uniform vec3 DistortionClearColor;\n"
    "uniform float EdgeFadeScale;\n"
    "uniform vec2 EyeToSourceUVScale;\n"
    "uniform vec2 EyeToSourceUVOffset;\n"
    "uniform vec2 EyeToSourceNDCScale;\n"
    "uniform vec2 EyeToSourceNDCOffset;\n"
    "uniform vec2 TanEyeAngleScale;\n"
    "uniform vec2 TanEyeAngleOffset;\n"
    "uniform vec4 HmdWarpParam;\n"
    "uniform vec4 ChromAbParam;\n"

    "varying vec4 oPosition;\n"
    "varying vec2 oTexCoord;\n"
    
    "void main()\n"
    "{\n"
    // Input oTexCoord is [-1,1] across the half of the screen used for a single eye.
    "   vec2 TanEyeAngleDistorted = oTexCoord * TanEyeAngleScale + TanEyeAngleOffset;\n" // Scales to tan(thetaX),tan(thetaY), but still distorted (i.e. only the center is correct)
    "   float  RadiusSq = TanEyeAngleDistorted.x * TanEyeAngleDistorted.x + TanEyeAngleDistorted.y * TanEyeAngleDistorted.y;\n"
    "   float Distort = 1.0 / ( 1.0 + RadiusSq * ( HmdWarpParam.y + RadiusSq * ( HmdWarpParam.z + RadiusSq * ( HmdWarpParam.w ) ) ) );\n"
    "   float DistortR = Distort * ( ChromAbParam.x + RadiusSq * ChromAbParam.y );\n"
    "   float DistortG = Distort;\n"
    "   float DistortB = Distort * ( ChromAbParam.z + RadiusSq * ChromAbParam.w );\n"
    "   vec2 TanEyeAngleR = DistortR * TanEyeAngleDistorted;\n"
    "   vec2 TanEyeAngleG = DistortG * TanEyeAngleDistorted;\n"
    "   vec2 TanEyeAngleB = DistortB * TanEyeAngleDistorted;\n"

    // These are now in "TanEyeAngle" space.
    // The vectors (TanEyeAngleRGB.x, TanEyeAngleRGB.y, 1.0) are real-world vectors pointing from the eye to where the components of the pixel appear to be.
    // If you had a raytracer, you could just use them directly.

    // Scale them into ([0,0.5],[0,1]) or ([0.5,0],[0,1]) UV lookup space (depending on eye)
    "   vec2 SourceCoordR = TanEyeAngleR * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "    SourceCoordR.y = 1.0 - SourceCoordR.y;\n"
    "   vec2 SourceCoordG = TanEyeAngleG * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "    SourceCoordG.y = 1.0 - SourceCoordG.y;\n"
    "   vec2 SourceCoordB = TanEyeAngleB * EyeToSourceUVScale + EyeToSourceUVOffset;\n"
    "    SourceCoordB.y = 1.0 - SourceCoordB.y;\n"

    // Find the distance to the nearest edge.
    "   vec2 NDCCoord = TanEyeAngleG * EyeToSourceNDCScale + EyeToSourceNDCOffset;\n"
    "   float EdgeFadeIn = clamp ( EdgeFadeScale, 0.0, 1e5 ) * ( 1.0 - max ( abs ( NDCCoord.x ), abs ( NDCCoord.y ) ) );\n"
    "   if ( EdgeFadeIn < 0.0 )\n"
    "   {\n"
    "       gl_FragColor = vec4(DistortionClearColor.r, DistortionClearColor.g, DistortionClearColor.b, 1.0);\n"
    "       return;\n"
    "   }\n"
    "   EdgeFadeIn = clamp ( EdgeFadeIn, 0.0, 1.0 );\n"

    // Actually do the lookups.
    "   float ResultR = texture2D(Texture, SourceCoordR).r;\n"
    "   float ResultG = texture2D(Texture, SourceCoordG).g;\n"
    "   float ResultB = texture2D(Texture, SourceCoordB).b;\n"

    "   gl_FragColor = vec4(ResultR * EdgeFadeIn, ResultG * EdgeFadeIn, ResultB * EdgeFadeIn, 1.0);\n"
    "}\n";



static const char* VShaderSrcs[VShader_Count] =
{
    DirectVertexShaderSrc,
    StdVertexShaderSrc,
    PostProcessVertexShaderSrc,
    PostProcessMeshVertexShaderSrc,
    PostProcessMeshTimewarpVertexShaderSrc,
    PostProcessMeshPositionalTimewarpVertexShaderSrc,
    PostProcessHeightmapTimewarpVertexShaderSrc,
};
static const char* FShaderSrcs[FShader_Count] =
{
    SolidFragShaderSrc,
    GouraudFragShaderSrc,
    TextureFragShaderSrc,
    AlphaTextureFragShaderSrc,
    AlphaBlendedTextureFragShaderSrc,
    PostProcessFragShaderWithChromAbSrc,
    LitSolidFragShaderSrc,
    LitTextureFragShaderSrc,
    MultiTextureFragShaderSrc,
    PostProcessMeshFragShaderSrc,
    PostProcessMeshTimewarpFragShaderSrc,
    PostProcessMeshPositionalTimewarpFragShaderSrc,
    PostProcessHeightmapTimewarpFragShaderSrc
};


RenderDevice::RenderDevice(const RendererParams&)
  : VertexShaders(),
    FragShaders(),
    DefaultFill(),
    Proj(),
    Vao(0),
    CurRenderTarget(),
    DepthBuffers(),
    CurrentFbo(0),
    MsaaFbo(0),
    GLVersionInfo(),
    DebugCallbackControl(),
    Lighting(NULL)
{
    DebugCallbackControl.Initialize();

    GetGLVersionAndExtensions(GLVersionInfo);

    OVR_ASSERT(GLVersionInfo.MajorVersion >= 2);
    
    for (int i = 0; i < VShader_Count; i++)
    {
        OVR_ASSERT ( VShaderSrcs[i] != NULL );      // You forgot a shader!
        VertexShaders[i] = *new Shader(this, Shader_Vertex, VShaderSrcs[i]);
    }

    for (int i = 0; i < FShader_Count; i++)
    {
        OVR_ASSERT ( FShaderSrcs[i] != NULL );      // You forgot a shader!
        FragShaders[i] = *new Shader(this, Shader_Fragment, FShaderSrcs[i]);
    }
    
    Ptr<ShaderSet> gouraudShaders = *new ShaderSet();
    gouraudShaders->SetShader(VertexShaders[VShader_MVP]);
    gouraudShaders->SetShader(FragShaders[FShader_Gouraud]);
    DefaultFill = *new ShaderFill(gouraudShaders);

    glGenFramebuffers(1, &CurrentFbo);
    glGenFramebuffers(1, &MsaaFbo);
    
    if (GLVersionInfo.SupportsVAO)
    {
        glGenVertexArrays(1, &Vao);
    }
}

RenderDevice::~RenderDevice()
{
    Shutdown();
}

void RenderDevice::Shutdown()
{
    // Release any other resources first.
    OVR::Render::RenderDevice::Shutdown();
    
    // This runs before the subclass's Shutdown(), where the context, etc, may be deleted.

    glDeleteFramebuffers(1, &CurrentFbo);
    glDeleteFramebuffers(1, &MsaaFbo);
    
    if (GLVersionInfo.SupportsVAO)
    {
        glDeleteVertexArrays(1, &Vao);
    }
    
    for (int i = 0; i < VShader_Count; ++i)
    {
        VertexShaders[i].Clear();
    }

    for (int i = 0; i < FShader_Count; ++i)
    {
        FragShaders[i].Clear();
    }

    DefaultFill.Clear();
    DepthBuffers.Clear();

    DebugCallbackControl.Shutdown();
}


void RenderDevice::FillTexturedRect(float left, float top, float right, float bottom, float ul, float vt, float ur, float vb, Color c, Ptr<OVR::Render::Texture> tex)
{
	Render::RenderDevice::FillTexturedRect(left, top, right, bottom, ul, vt, ur, vb, c, tex);
}


Shader *RenderDevice::LoadBuiltinShader(ShaderStage stage, int shader)
{
    switch (stage)
    {
    case Shader_Vertex: return VertexShaders[shader];
    case Shader_Fragment: return FragShaders[shader];
    default:
        return NULL;
    }
}


void RenderDevice::BeginRendering()
{
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    glFrontFace(GL_CW);

    glEnable(GL_LINE_SMOOTH);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
}

void RenderDevice::SetDepthMode(bool enable, bool write, CompareFunc func)
{
    if (enable)
    {
        glEnable(GL_DEPTH_TEST);
        glDepthMask(write);
        switch (func)
        {
        case Compare_Always:  glDepthFunc(GL_ALWAYS); break;
        case Compare_Less:    glDepthFunc(GL_LESS); break;
        case Compare_Greater: glDepthFunc(GL_GREATER); break;
        default: assert(0);
        }
    }
    else
        glDisable(GL_DEPTH_TEST);
}

void RenderDevice::SetViewport(const Recti& vp)
{
	glViewport(vp.x, vp.y, vp.w, vp.h);
}

void RenderDevice::Flush()
{
    glFlush();
}

void RenderDevice::WaitUntilGpuIdle()
{
    glFlush();
    glFinish();
}

void RenderDevice::Clear(float r, float g, float b, float a, float depth, bool clearColor /*= true*/, bool clearDepth /*= true*/)
{
    glClearColor(r,g,b,a);
    glClearDepth(depth);
    glClear(
        ( clearColor ? ( GL_COLOR_BUFFER_BIT ) : 0 ) |
        ( clearDepth ? ( GL_DEPTH_BUFFER_BIT ) : 0 )
        );
}

Texture* RenderDevice::GetDepthBuffer(int w, int h, int ms)
{
    for (unsigned i = 0; i < DepthBuffers.GetSize(); i++)
        if (w == DepthBuffers[i]->Width && h == DepthBuffers[i]->Height && ms == DepthBuffers[i]->GetSamples())
            return DepthBuffers[i];

    Ptr<Texture> newDepth = *CreateTexture(Texture_Depth|Texture_RenderTarget|ms, w, h, NULL);
    DepthBuffers.PushBack(newDepth);
    return newDepth.GetPtr();
}

void RenderDevice::ResolveMsaa(OVR::Render::Texture* msaaTex, OVR::Render::Texture* outputTex)
{
    bool isMsaaTarget = msaaTex->GetSamples() > 1;
    glBindFramebuffer( GL_READ_FRAMEBUFFER, MsaaFbo );
    glFramebufferTexture2D( GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                            isMsaaTarget ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D,
                            ((Texture*)msaaTex)->TexId, 0);
    glFramebufferRenderbuffer(GL_READ_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, 0);
    OVR_ASSERT(glCheckFramebufferStatus(GL_READ_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);

    glBindFramebuffer( GL_DRAW_FRAMEBUFFER, CurrentFbo );
    glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, ((Texture*)outputTex)->TexId, 0);
    glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, 0);

    OVR_ASSERT(glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);

    //glReadBuffer(GL_TEXTURE_2D_MULTISAMPLE);
    //glDrawBuffer(GL_COLOR_ATTACHMENT0);
    glBlitFramebuffer( 0, 0, msaaTex->GetWidth(), msaaTex->GetHeight(),
                       0, 0, outputTex->GetWidth(), outputTex->GetHeight(), GL_COLOR_BUFFER_BIT, GL_NEAREST );
    glBindFramebuffer( GL_FRAMEBUFFER, 0 );
    GLint err = glGetError();
    OVR_ASSERT(!err); OVR_UNUSED(err);
}

void RenderDevice::SetRenderTarget(Render::Texture* color, Render::Texture* depth, Render::Texture* stencil)
{
    OVR_UNUSED(stencil);

    CurRenderTarget = (Texture*)color;
    if (color == NULL)
    {
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        return;
    }

    int sampleCount = CurRenderTarget->GetSamples();

    if (depth == NULL)
        depth = GetDepthBuffer(color->GetWidth(), color->GetHeight(), sampleCount);

    glBindFramebuffer(GL_FRAMEBUFFER, CurrentFbo);

    GLenum texTarget = (sampleCount > 1) ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D;

    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, texTarget, ((Texture*)color)->TexId, 0);
    if (depth)
        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, texTarget, ((Texture*)depth)->TexId, 0);
    else
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, 0);

    GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if (status != GL_FRAMEBUFFER_COMPLETE)
        OVR_DEBUG_LOG(("framebuffer not complete: %x", status));
}


void RenderDevice::SetWorldUniforms(const Matrix4f& proj)
{
    Proj = proj.Transposed();
}

void RenderDevice::SetTexture(Render::ShaderStage, int slot, const Texture* t)
{
    glActiveTexture(GL_TEXTURE0 + slot);
    glBindTexture((t->GetSamples() > 1) ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D, ((Texture*)t)->TexId);
}

Buffer* RenderDevice::CreateBuffer()
{
    return new Buffer(this);
}

Fill* RenderDevice::CreateSimpleFill(int flags)
{
    OVR_UNUSED(flags);
    return DefaultFill;
}
    
void RenderDevice::Render(const Matrix4f& matrix, Model* model)
{
    if (GLVersionInfo.SupportsVAO)
    {
        glBindVertexArray(Vao);
    }

    // Store data in buffers if not already
    if (!model->VertexBuffer)
    {
        Ptr<Render::Buffer> vb = *CreateBuffer();
        vb->Data(Buffer_Vertex | Buffer_ReadOnly, &model->Vertices[0], model->Vertices.GetSize() * sizeof(Vertex));
        model->VertexBuffer = vb;
    }

    if (!model->IndexBuffer)
    {
        Ptr<Render::Buffer> ib = *CreateBuffer();
        ib->Data(Buffer_Index | Buffer_ReadOnly, &model->Indices[0], model->Indices.GetSize() * 2);
        model->IndexBuffer = ib;
    }

    Render(model->Fill ? (const Fill*)model->Fill : (const Fill*)DefaultFill,
           model->VertexBuffer, model->IndexBuffer,
           matrix, 0, (int)model->Indices.GetSize(), model->GetPrimType());
}

void RenderDevice::Render(const Fill* fill, Render::Buffer* vertices, Render::Buffer* indices,
                      const Matrix4f& matrix, int offset, int count, PrimitiveType rprim, MeshType meshType /*= Mesh_Scene*/)
{
    ShaderSet* shaders = (ShaderSet*) ((ShaderFill*)fill)->GetShaders();

    GLenum prim;
    switch (rprim)
    {
    case Prim_Triangles:
        prim = GL_TRIANGLES;
        break;
    case Prim_Lines:
        prim = GL_LINES;
        break;
    case Prim_TriangleStrip:
        prim = GL_TRIANGLE_STRIP;
        break;
    default:
        assert(0);
        return;
    }

    fill->Set();
    if (shaders->ProjLoc >= 0)
        glUniformMatrix4fv(shaders->ProjLoc, 1, 0, &Proj.M[0][0]);
    if (shaders->ViewLoc >= 0)
        glUniformMatrix4fv(shaders->ViewLoc, 1, 0, &matrix.Transposed().M[0][0]);

    if (shaders->UsesLighting && Lighting->Version != shaders->LightingVer)
    {
        shaders->LightingVer = Lighting->Version;
        Lighting->Set(shaders);
    }

    glBindBuffer(GL_ARRAY_BUFFER, ((Buffer*)vertices)->GLBuffer);
    for (int i = 0; i < 5; i++)
        glEnableVertexAttribArray(i);

    switch (meshType)
    {
    case Mesh_Distortion:
        glVertexAttribPointer(0, 2, GL_FLOAT, false, sizeof(DistortionVertex), reinterpret_cast<char*>(offset) + offsetof(DistortionVertex, Pos));
        glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, true, sizeof(DistortionVertex), reinterpret_cast<char*>(offset) + offsetof(DistortionVertex, Col));
        glVertexAttribPointer(2, 2, GL_FLOAT, false, sizeof(DistortionVertex), reinterpret_cast<char*>(offset) + offsetof(DistortionVertex, TexR));
        glVertexAttribPointer(3, 2, GL_FLOAT, false, sizeof(DistortionVertex), reinterpret_cast<char*>(offset) + offsetof(DistortionVertex, TexG));
        glVertexAttribPointer(4, 2, GL_FLOAT, false, sizeof(DistortionVertex), reinterpret_cast<char*>(offset) + offsetof(DistortionVertex, TexB));
        break;

    case Mesh_Heightmap:
        glVertexAttribPointer(0, 2, GL_FLOAT, false, sizeof(HeightmapVertex), reinterpret_cast<char*>(offset) + offsetof(HeightmapVertex, Pos));
        glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(HeightmapVertex), reinterpret_cast<char*>(offset) + offsetof(HeightmapVertex, Tex));
        break;

    default:
        glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(Vertex), reinterpret_cast<char*>(offset) + offsetof(Vertex, Pos));
        glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, true, sizeof(Vertex), reinterpret_cast<char*>(offset) + offsetof(Vertex, C));
        glVertexAttribPointer(2, 2, GL_FLOAT, false, sizeof(Vertex), reinterpret_cast<char*>(offset) + offsetof(Vertex, U));
        glVertexAttribPointer(3, 2, GL_FLOAT, false, sizeof(Vertex), reinterpret_cast<char*>(offset) + offsetof(Vertex, U2));
        glVertexAttribPointer(4, 3, GL_FLOAT, false, sizeof(Vertex), reinterpret_cast<char*>(offset) + offsetof(Vertex, Norm));
    }

    if (indices)
    {
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ((Buffer*)indices)->GLBuffer);
        glDrawElements(prim, count, GL_UNSIGNED_SHORT, NULL);
    }
    else
    {
        glDrawArrays(prim, 0, count);
    }

    for (int i = 0; i < 5; i++)
        glDisableVertexAttribArray(i);
}

void RenderDevice::RenderWithAlpha(const Fill* fill, Render::Buffer* vertices, Render::Buffer* indices,
                                   const Matrix4f& matrix, int offset, int count, PrimitiveType rprim)
{
    //glEnable(GL_BLEND);
    Render(fill, vertices, indices, matrix, offset, count, rprim);
    //glDisable(GL_BLEND);
}

void RenderDevice::SetLighting(const LightingParams* lt)
{
    Lighting = lt;
}

Buffer::~Buffer()
{
    if (GLBuffer)
        glDeleteBuffers(1, &GLBuffer);
}

bool Buffer::Data(int use, const void* buffer, size_t size)
{
    switch (use & Buffer_TypeMask)
    {
    case Buffer_Index:     Use = GL_ELEMENT_ARRAY_BUFFER; break;
    default:               Use = GL_ARRAY_BUFFER; break;
    }

    if (!GLBuffer)
        glGenBuffers(1, &GLBuffer);

    int mode = GL_DYNAMIC_DRAW;
    if (use & Buffer_ReadOnly)
        mode = GL_STATIC_DRAW;

    glBindBuffer(Use, GLBuffer);
    glBufferData(Use, size, buffer, mode);
    return 1;
}

void* Buffer::Map(size_t, size_t, int)
{
    int mode = GL_WRITE_ONLY;
    //if (flags & Map_Unsynchronized)
    //    mode |= GL_MAP_UNSYNCHRONIZED;
    
    glBindBuffer(Use, GLBuffer);
    void* v = glMapBuffer(Use, mode);
    return v;
}

bool Buffer::Unmap(void*)
{
    glBindBuffer(Use, GLBuffer);
    int r = glUnmapBuffer(Use);
    return r != 0;
}

Shader::~Shader()
{
    if (GLShader)
        glDeleteShader(GLShader);
}

bool Shader::Compile(const char* src)
{
    if (!GLShader)
        GLShader = glCreateShader(GLStage());

    glShaderSource(GLShader, 1, &src, 0);
    glCompileShader(GLShader);
    GLint r;
    glGetShaderiv(GLShader, GL_COMPILE_STATUS, &r);
    if (!r)
    {
        GLchar msg[1024];
        glGetShaderInfoLog(GLShader, sizeof(msg), 0, msg);
        if (msg[0])
            OVR_DEBUG_LOG(("Compiling shader\n%s\nfailed: %s\n", src, msg));
        if (!r)
            return 0;
    }
    return 1;
}

ShaderSet::ShaderSet() :
  //Prog(0),
    UniformInfo(),
    ProjLoc(0),
    ViewLoc(0),
  //TexLoc[8];
    UsesLighting(false),
    LightingVer(0)
{
    memset(TexLoc, 0, sizeof(TexLoc));
    Prog = glCreateProgram();
}
ShaderSet::~ShaderSet()
{
    glDeleteProgram(Prog);
}

void ShaderSet::SetShader(Render::Shader *s)
{
    Shaders[s->GetStage()] = s;
    Shader* gls = (Shader*)s;
    glAttachShader(Prog, gls->GLShader);
    if (Shaders[Shader_Vertex] && Shaders[Shader_Fragment])
        Link();
}

void ShaderSet::UnsetShader(int stage)
{
    Shader* gls = (Shader*)(Render::Shader*)Shaders[stage];
    if (gls)
        glDetachShader(Prog, gls->GLShader);
    Shaders[stage] = NULL;
}

bool ShaderSet::Link()
{
    glBindAttribLocation(Prog, 0, "Position");
    glBindAttribLocation(Prog, 1, "Color");
    glBindAttribLocation(Prog, 2, "TexCoord");
    glBindAttribLocation(Prog, 3, "TexCoord1");
    glBindAttribLocation(Prog, 4, "Normal");

    glLinkProgram(Prog);
    GLint r;
    glGetProgramiv(Prog, GL_LINK_STATUS, &r);
    if (!r)
    {
        GLchar msg[1024];
        glGetProgramInfoLog(Prog, sizeof(msg), 0, msg);
        OVR_DEBUG_LOG(("Linking shaders failed: %s\n", msg));
        if (!r)
            return 0;
    }
    glUseProgram(Prog);

    UniformInfo.Clear();
    LightingVer = 0;
    UsesLighting = 0;

    GLint uniformCount = 0;
    glGetProgramiv(Prog, GL_ACTIVE_UNIFORMS, &uniformCount);
    OVR_ASSERT(uniformCount >= 0);

    for(GLuint i = 0; i < (GLuint)uniformCount; i++)
    {
        GLsizei namelen;
        GLint size = 0;
        GLenum type;
        GLchar name[32];
        glGetActiveUniform(Prog, i, sizeof(name), &namelen, &size, &type, name);

        if (size)
        {
            int l = glGetUniformLocation(Prog, name);
            char *np = name;
            while (*np)
            {
                if (*np == '[')
                    *np = 0;
                np++;
            }
            Uniform u;
            u.Name = name;
            u.Location = l;
            u.Size = size;
            switch (type)
            {
            case GL_FLOAT:      u.Type = 1; break;
            case GL_FLOAT_VEC2: u.Type = 2; break;
            case GL_FLOAT_VEC3: u.Type = 3; break;
            case GL_FLOAT_VEC4: u.Type = 4; break;
            case GL_FLOAT_MAT3: u.Type = 12; break;
            case GL_FLOAT_MAT4: u.Type = 16; break;
            default:
                continue;
            }
            UniformInfo.PushBack(u);
            if (!strcmp(name, "LightCount"))
                UsesLighting = 1;
        }
        else
            break;
    }

    ProjLoc = glGetUniformLocation(Prog, "Proj");
    ViewLoc = glGetUniformLocation(Prog, "View");
    for (int i = 0; i < 8; i++)
    {
        char texv[32];
        OVR_sprintf(texv, 10, "Texture%d", i);
        TexLoc[i] = glGetUniformLocation(Prog, texv);
        if (TexLoc[i] < 0)
            break;

        glUniform1i(TexLoc[i], i);
    }
    if (UsesLighting)
        OVR_ASSERT(ProjLoc >= 0 && ViewLoc >= 0);
    return 1;
}

void ShaderSet::Set(PrimitiveType) const
{
    glUseProgram(Prog);
}

bool ShaderSet::SetUniform(const char* name, int n, const float* v)
{
    for (unsigned int i = 0; i < UniformInfo.GetSize(); i++)
        if (!strcmp(UniformInfo[i].Name.ToCStr(), name))
        {
            OVR_ASSERT(UniformInfo[i].Location >= 0);
            glUseProgram(Prog);
            switch (UniformInfo[i].Type)
            {
            case 1:   glUniform1fv(UniformInfo[i].Location, n, v); break;
            case 2:   glUniform2fv(UniformInfo[i].Location, n/2, v); break;
            case 3:   glUniform3fv(UniformInfo[i].Location, n/3, v); break;
            case 4:   glUniform4fv(UniformInfo[i].Location, n/4, v); break;
            case 12:  glUniformMatrix3fv(UniformInfo[i].Location, 1, 1, v); break;
            case 16:  glUniformMatrix4fv(UniformInfo[i].Location, 1, 1, v); break;
            default: OVR_ASSERT(0);
            }
            return 1;
        }

    OVR_DEBUG_LOG(("Warning: uniform %s not present in selected shader", name));
    return 0;
}

bool ShaderSet::SetUniform4x4f(const char* name, const Matrix4f& m)
{
    for (unsigned int i = 0; i < UniformInfo.GetSize(); i++)
        if (!strcmp(UniformInfo[i].Name.ToCStr(), name))
        {
            glUseProgram(Prog);
            glUniformMatrix4fv(UniformInfo[i].Location, 1, 1, &m.M[0][0]);
            return 1;
        }

    OVR_DEBUG_LOG(("Warning: uniform %s not present in selected shader", name));
    return 0;
}

Texture::Texture(RenderDevice* r, int w, int h, int samples) : Ren(r), Width(w), Height(h), Samples(samples)
{
    glGenTextures(1, &TexId);
}

Texture::~Texture()
{
    if (TexId)
        glDeleteTextures(1, &TexId);
}

void Texture::Set(int slot, Render::ShaderStage stage) const
{
    Ren->SetTexture(stage, slot, this);
}

void Texture::SetSampleMode(int sm)
{
    glBindTexture((GetSamples() > 1) ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D, TexId);
    switch (sm & Sample_FilterMask)
    {
    case Sample_Linear:
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 1);
        break;

    case Sample_Anisotropic:
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 4);
        break;

    case Sample_Nearest:
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 1);
        break;
    }

    switch (sm & Sample_AddressMask)
    {
    case Sample_Repeat:
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
        break;

    case Sample_Clamp:
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        break;

    case Sample_ClampBorder:
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
        break;
    }
}

ovrTexture Texture::Get_ovrTexture()
{
    ovrTexture tex;
    OVR::Sizei newRTSize(Width, Height);

    ovrGLTextureData* texData = (ovrGLTextureData*)&tex;
    texData->Header.API            = ovrRenderAPI_OpenGL;
    texData->Header.TextureSize    = newRTSize;
    texData->Header.RenderViewport = Recti(newRTSize);
    texData->TexId                 = TexId;

    return tex;
}

Texture* RenderDevice::CreateTexture(int format, int width, int height, const void* data, int mipcount)
{
    GLenum   glformat, gltype = GL_UNSIGNED_BYTE;
    switch(format & Texture_TypeMask)
    {
    case Texture_RGBA:  glformat = GL_RGBA; break;
    case Texture_R:     glformat = GL_RED; break;
    case Texture_Depth: glformat = GL_DEPTH_COMPONENT; gltype = GL_FLOAT; break;
    case Texture_DXT1:  glformat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT; break;
    case Texture_DXT3:  glformat = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT; break;
    case Texture_DXT5:  glformat = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT; break;
    default:
        return NULL;
    }
    int samples = format & Texture_SamplesMask;
    if(samples < 1 ||
        GLVersionInfo.WholeVersion < 302) // disallow MSAA for low GL context versions
    {
        samples = 1;
    }

    GLenum textureTarget = (samples > 1) ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D;

    Texture* NewTex = new Texture(this, width, height, samples);
    glBindTexture(textureTarget, NewTex->TexId);
    GLint err = glGetError();

    #if ! defined(OVR_OS_MAC)
    OVR_ASSERT(!err);
    #endif

    if( err )
    {
        printf("RenderDevice::CreateTexture glGetError result: %d\n", err);
    }
    
    if (format & Texture_Compressed)
    {
        const unsigned char* level = (const unsigned char*)data;
        int w = width, h = height;
        for (int i = 0; i < mipcount; i++)
        {
            int mipsize = GetTextureSize(format, w, h);
            glCompressedTexImage2D(GL_TEXTURE_2D, i, glformat, w, h, 0, mipsize, level);

            level += mipsize;
            w >>= 1;
            h >>= 1;
            if (w < 1) w = 1;
            if (h < 1) h = 1;
        }
    }
    else
    {
        bool isSRGB = ((format & Texture_TypeMask) == Texture_RGBA && (format & Texture_SRGB) != 0);
        bool isDepth = ((format & Texture_Depth) != 0);
        GLenum internalFormat = (isSRGB) ? GL_SRGB8_ALPHA8 : (isDepth) ? GL_DEPTH_COMPONENT32F : glformat;

        if (samples > 1)
            glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, internalFormat, width, height, false);
        else
            glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, width, height, 0, glformat, gltype, data);
    }

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    if (format == (Texture_RGBA|Texture_GenMipmaps)) // not render target
    {
        int srcw = width, srch = height;
        int level = 0;
        uint8_t* mipmaps = NULL;
        do
        {
            level++;
            int mipw = srcw >> 1; if (mipw < 1) mipw = 1;
            int miph = srch >> 1; if (miph < 1) miph = 1;
            if (mipmaps == NULL)
                mipmaps = (uint8_t*)OVR_ALLOC(mipw * miph * 4);
            FilterRgba2x2(level == 1 ? (const uint8_t*)data : mipmaps, srcw, srch, mipmaps);
            glTexImage2D(GL_TEXTURE_2D, level, glformat, mipw, miph, 0, glformat, gltype, mipmaps);
            srcw = mipw;
            srch = miph;
        } while (srcw > 1 || srch > 1);
        if (mipmaps)
            OVR_FREE(mipmaps);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, level);
    }
    else
    {
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, mipcount-1);
    }

    OVR_ASSERT(!glGetError());
    return NewTex;
}

RBuffer::RBuffer(GLenum format, GLint w, GLint h)
{
    Width = w;
    Height = h;
    glGenRenderbuffers(1, &BufId);
    glBindRenderbuffer(GL_RENDERBUFFER, BufId);
    glRenderbufferStorage(GL_RENDERBUFFER, format, w, h);
    glBindRenderbuffer(GL_RENDERBUFFER, 0);
}

RBuffer::~RBuffer()
{
    if (BufId)
        glDeleteRenderbuffers(1, &BufId);
}






DebugCallback::DebugCallback()
  : Initialized(false),
    MinLogSeverity(SeverityHigh),
    MinAssertSeverity(SeverityHigh),
    glDebugMessageCallback(NULL),
    glDebugMessageControl(NULL),
    glDebugMessageCallbackARB(NULL),
    glDebugMessageControlARB(NULL),
    glDebugMessageCallbackAMD(NULL),
    glDebugMessageControlAMD(NULL)
{
}


DebugCallback::~DebugCallback()
{
    Shutdown();
}


bool DebugCallback::GetGLDebugCallback(PFNGLDEBUGMESSAGECALLBACKPROC* debugCallback, const void** userParam) const
{
    // Curiously, the KHR and ARB callbacks use the same glGetPointerv defines, which means you can only have 
    // one of them active concurrently. This also implies that an OpenGL implementation which implements both
    // KHR and ARB implements the latter as simply a passthrough (or alias) of the former.
    #if defined(GL_ARB_debug_output) || defined(GL_KHR_debug)
        // glGetPointerv requires at least OpenGL 4.3 headers and implementation, 
        // but will be present in the headers if GL_ARB_debug_output or GL_KHR_debug are.
        if(glDebugMessageCallback || glDebugMessageCallbackARB)
        {
            glGetPointerv(GL_DEBUG_CALLBACK_FUNCTION, reinterpret_cast<GLvoid**>(debugCallback));
            glGetPointerv(GL_DEBUG_CALLBACK_USER_PARAM, const_cast<GLvoid**>(userParam));
            return true;
        }
    #endif

    // AMD_debug_output doesn't provide an option to get the debug callback.
    debugCallback = NULL;
    userParam = NULL;
    return false;
}


void DebugCallback::DebugCallbackInternal(Severity s, const char* pSource, const char* pType, GLuint id, const char* pSeverity, const char* message)
{
    if(s >= MinLogSeverity)
    {
        OVR::LogError("{ERR-xxxx} [GL Error] %s %s %#x %s: %s", pSource, pType, id, pSeverity, message);
    }

    if(s >= MinAssertSeverity)
    {
        OVR_ASSERT(s < MinAssertSeverity); // Unilateral fail.
    }
}


void DebugCallback::Initialize()
{
    if(!Initialized)
    {
        Initialized = true;

        int err = glGetError();
        OVR_UNUSED(err);

        // Used to see if a callback was already registered.
        PFNGLDEBUGMESSAGECALLBACKPROC debugCallbackPrev = NULL;
        const void* userParamPrev = NULL;

        // Try getting the KHR interface.
        #if defined(OVR_OS_MAC) // With Mac OpenGL, functions aren't dynamically linked. They are only directly called.
          //glDebugMessageCallback = ::glDebugMessageCallback; // We can enable this some day when Apple includes support 
          //glDebugMessageControl  = ::glDebugMessageControl;  // for glDebugMessageCallback in their headers and SDK.
        #else
            glDebugMessageCallback = (PFNGLDEBUGMESSAGECALLBACKPROC) GetFunction("glDebugMessageCallback");
            glDebugMessageControl  = (PFNGLDEBUGMESSAGECONTROLPROC) GetFunction("glDebugMessageControl");
        #endif

        if(glDebugMessageCallback) 
        {
            GetGLDebugCallback(&debugCallbackPrev, &userParamPrev);

            if(!debugCallbackPrev) // If a callback isn't already registered...
            {
                glDebugMessageCallback(GLDEBUGPROC(DebugMessageCallback), this);
                err = glGetError();
                if(err)
                {
                	glDebugMessageCallback = NULL;
                	glDebugMessageControl = NULL;
                	OVR_DEBUG_LOG(("glDebugMessageCallback error: %x (%d)\n", err, err));
            	}

                glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
                err = glGetError();
                if(err)
                {
                	OVR_DEBUG_LOG(("GL_DEBUG_OUTPUT_SYNCHRONOUS error: %x (%d)\n", err, err));
                }

                // To consider: disable marker/push/pop
                // glDebugMessageControl(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_MARKER,     GL_DONT_CARE, 0, NULL, GL_FALSE);
                // glDebugMessageControl(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_PUSH_GROUP, GL_DONT_CARE, 0, NULL, GL_FALSE);
                // glDebugMessageControl(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_POP_GROUP,  GL_DONT_CARE, 0, NULL, GL_FALSE);
            }
        }

        if(!glDebugMessageCallback) // If KHR_debug wasn't found, try ARB_debug_output.
        {
            #if !defined(OVR_OS_MAC)
                glDebugMessageCallbackARB = (PFNGLDEBUGMESSAGECALLBACKARBPROC) GetFunction("glDebugMessageCallbackARB");
                glDebugMessageControlARB  = (PFNGLDEBUGMESSAGECONTROLARBPROC) GetFunction("glDebugMessageControlARB");
            #endif

            if(glDebugMessageCallbackARB)
            {
                GetGLDebugCallback(&debugCallbackPrev, &userParamPrev);

                if(!debugCallbackPrev) // If a callback isn't already registered...
                {
                    glDebugMessageCallbackARB(GLDEBUGPROCARB(DebugMessageCallback), this);
                    err = glGetError();
                    if(err)
                    {
                    	glDebugMessageCallbackARB = NULL;
                    	glDebugMessageControlARB = NULL;
                    	OVR_DEBUG_LOG(("glDebugMessageCallbackARB error: %x (%d)\n", err, err));
                	}

                    glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS);
                    err = glGetError();
                    if(err)
                    {
                    	OVR_DEBUG_LOG(("GL_DEBUG_OUTPUT_SYNCHRONOUS error: %x (%d)\n", err, err));
                    }

                    // To consider: disable marker/push/pop
                    // glDebugMessageControlARB(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_MARKER,     GL_DONT_CARE, 0, NULL, GL_FALSE);
                    // glDebugMessageControlARB(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_PUSH_GROUP, GL_DONT_CARE, 0, NULL, GL_FALSE);
                    // glDebugMessageControlARB(GL_DEBUG_SOURCE_APPLICATION, GL_DEBUG_TYPE_POP_GROUP,  GL_DONT_CARE, 0, NULL, GL_FALSE);
                }
            }
        }

		if(!glDebugMessageCallback && !glDebugMessageCallbackARB)// If ARB_debug_output also wasn't found, try AMD_debug_output.
		{
			#if !defined(OVR_OS_MAC)
				glDebugMessageCallbackAMD = (PFNGLDEBUGMESSAGECALLBACKAMDPROC) GetFunction("glDebugMessageCallbackAMD");
				glDebugMessageControlAMD  = (PFNGLDEBUGMESSAGEENABLEAMDPROC) GetFunction("glDebugMessageControlAMD");
			#endif

			if(glDebugMessageCallbackAMD)
			{
				if(!debugCallbackPrev) // If a callback isn't already registered...
				{
					glDebugMessageCallbackAMD(GLDEBUGPROCAMD(DebugMessageCallbackAMD), this);
                    err = glGetError();
                    if(err)
                    {
                    	glDebugMessageCallbackAMD = NULL;
                    	glDebugMessageControlAMD = NULL;
                    	OVR_DEBUG_LOG(("glDebugMessageCallbackAMD error: %x (%d)\n", err, err));
                	}
					// There is no control for synchronous/asynchronous with AMD_debug_output.
				}
			}
		}
    }
}


void DebugCallback::Shutdown()
{
    if(Initialized)
    {
        if(glDebugMessageCallbackAMD)
        {
            glDebugMessageCallbackAMD(NULL, NULL);
            glDebugMessageCallbackAMD = NULL;
        }

        if(glDebugMessageCallbackARB)
        {
            glDebugMessageCallbackARB(NULL, NULL);
            glDebugMessageCallbackARB = NULL;
        }

        if(glDebugMessageCallback)
        {
            glDebugMessageCallback(NULL, NULL);
            glDebugMessageCallback = NULL;
        }

        Initialized = false;
    }
}


void DebugCallback::SetMinSeverity(Severity minLogSeverity, Severity minAssertSeverity)
{
    MinLogSeverity    = minLogSeverity;
    MinAssertSeverity = minAssertSeverity;
}


DebugCallback::Implementation DebugCallback::GetImplementation() const
{
    if(glDebugMessageCallbackAMD)
        return ImplementationAMD;

    if(glDebugMessageCallbackARB)
        return ImplementationARB;

    if(glDebugMessageCallback)
        return ImplementationKHR;

    return ImplementationNone;
}


void DebugCallback::DebugMessageCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei /*length*/, const GLchar* message, GLvoid* userParam)
{
    const char* pSource   = GetSource(source);
    const char* pType     = GetType(type);
    const char* pSeverity = GetSeverity(severity);
    Severity    s;

    switch(severity)
    {
        default:
        case GL_DEBUG_SEVERITY_NOTIFICATION:
            s = SeverityNotification;
            break;
        case GL_DEBUG_SEVERITY_LOW:
            s = SeverityLow;
            break;
        case GL_DEBUG_SEVERITY_MEDIUM:
            s = SeverityMedium;
            break;
        case GL_DEBUG_SEVERITY_HIGH:
            s = SeverityHigh;
            break;
    }

    DebugCallback* pThis = reinterpret_cast<DebugCallback*>(userParam);
    pThis->DebugCallbackInternal(s, pSource, pType, id, pSeverity, message);
}


const char* DebugCallback::GetSource(GLenum Source)
{
    // There is one contiguous section of GL_DEBUG_SOURCE values.
    static_assert((GL_DEBUG_SOURCE_OTHER - GL_DEBUG_SOURCE_API) == 5, "GL_DEBUG_SOURCE constants are not contiguous.");

    static const char* GL_SourceStrings[] =
    {
        "API",             // GL_DEBUG_SOURCE_API
        "System",          // GL_DEBUG_SOURCE_WINDOW_SYSTEM
        "ShaderCompiler",  // GL_DEBUG_SOURCE_SHADER_COMPILER
        "ThirdParty",      // GL_DEBUG_SOURCE_THIRD_PARTY
        "Application",     // GL_DEBUG_SOURCE_APPLICATION
        "Other"            // GL_DEBUG_SOURCE_OTHER
    };
    
    if ((Source >= GL_DEBUG_SOURCE_API) && (Source <= GL_DEBUG_SOURCE_OTHER))
        return GL_SourceStrings[Source - GL_DEBUG_SOURCE_API];
        
    return "Unknown";
}



const char* DebugCallback::GetType(GLenum Type)
{
    // There are two contiguous sections of GL_DEBUG_TYPE values.
    static_assert((GL_DEBUG_TYPE_OTHER - GL_DEBUG_TYPE_ERROR) == 5, "GL_DEBUG_TYPE constants are not contiguous.");
    static const char* TypeStrings[] =
    {
        "Error",                // GL_DEBUG_TYPE_ERROR
        "Deprecated",           // GL_DEBUG_TYPE_DEPRECATED_BEHAVIOR
        "UndefinedBehavior",    // GL_DEBUG_TYPE_UNDEFINED_BEHAVIOR
        "Portability",          // GL_DEBUG_TYPE_PORTABILITY
        "Performance",          // GL_DEBUG_TYPE_PERFORMANCE
        "Other"                 // GL_DEBUG_TYPE_OTHER
    };

    if ((Type >= GL_DEBUG_TYPE_ERROR) && (Type <= GL_DEBUG_TYPE_OTHER))
        return TypeStrings[Type - GL_DEBUG_TYPE_ERROR];

    // KHR_debug marker/push/pop functionality.
    static_assert((GL_DEBUG_TYPE_POP_GROUP - GL_DEBUG_TYPE_MARKER) == 2, "GL_DEBUG_TYPE constants are not contiguous.");
    static const char* TypeStrings2[] =
    {
        "Marker",       // GL_DEBUG_TYPE_MARKER
        "PushGroup",    // GL_DEBUG_TYPE_PUSH_GROUP
        "PopGroup",     // GL_DEBUG_TYPE_POP_GROUP
    };

    if ((Type >= GL_DEBUG_TYPE_MARKER) && (Type <= GL_DEBUG_TYPE_POP_GROUP))
        return TypeStrings2[Type - GL_DEBUG_TYPE_MARKER];

    return "Unknown";
}


const char* DebugCallback::GetSeverity(GLenum Severity)
{
    // There are two sections of GL_DEBUG_SEVERITY.
    static_assert((GL_DEBUG_SEVERITY_LOW - GL_DEBUG_SEVERITY_HIGH) == 2, "GL_DEBUG_SEVERITY constants are not contiguous.");
    static const char* SeverityStrings[] =
    {
        "High",
        "Medium",
        "Low"
    };

    if ((Severity >= GL_DEBUG_SEVERITY_HIGH) && (Severity <= GL_DEBUG_SEVERITY_LOW))
        return SeverityStrings[Severity - GL_DEBUG_SEVERITY_HIGH];

    // There is just one value in this second section.
    if(Severity == GL_DEBUG_SEVERITY_NOTIFICATION)
        return "Notification";

    return "Unknown";
}


void DebugCallback::DebugMessageCallbackAMD(GLuint id, GLenum category, GLenum severity, GLsizei /*length*/, const GLchar *message, GLvoid *userParam)
{
    static_assert(GL_DEBUG_SEVERITY_LOW_AMD == GL_DEBUG_SEVERITY_LOW, "Severity mismatch"); // Verify that AMD_debug_output severity constants are identical to KHR_debug severity contstants.

    const char* pSource   = GetCategoryAMD(category);
    const char* pSeverity = GetSeverity(severity);
    Severity    s;

    switch(severity)
    {
        default:
        case GL_DEBUG_SEVERITY_NOTIFICATION:
            s = SeverityNotification;
            break;
        case GL_DEBUG_SEVERITY_LOW:
            s = SeverityLow;
            break;
        case GL_DEBUG_SEVERITY_MEDIUM:
            s = SeverityMedium;
            break;
        case GL_DEBUG_SEVERITY_HIGH:
            s = SeverityHigh;
            break;
    }

    DebugCallback* pThis = reinterpret_cast<DebugCallback*>(userParam);
    pThis->DebugCallbackInternal(s, pSource, "Other", id, pSeverity, message);
}


const char* DebugCallback::GetCategoryAMD(GLenum Category)
{
    static_assert((GL_DEBUG_CATEGORY_OTHER_AMD - GL_DEBUG_CATEGORY_API_ERROR_AMD) == 7, "GL_DEBUG_CATEGORY constants are not contiguous.");
    static const char* CategoryStrings[] =
    {
        "API",                  // GL_DEBUG_CATEGORY_API_ERROR_AMD
        "System",               // GL_DEBUG_CATEGORY_WINDOW_SYSTEM_AMD
        "Deprecation",          // GL_DEBUG_CATEGORY_DEPRECATION_AMD
        "UndefinedBehavior",    // GL_DEBUG_CATEGORY_UNDEFINED_BEHAVIOR_AMD
        "Performance",          // GL_DEBUG_CATEGORY_PERFORMANCE_AMD
        "ShaderCompiler",       // GL_DEBUG_CATEGORY_SHADER_COMPILER_AMD
        "Application",          // GL_DEBUG_CATEGORY_APPLICATION_AMD
        "Other"                 // GL_DEBUG_CATEGORY_OTHER_AMD
    };

    if((Category >= GL_DEBUG_CATEGORY_API_ERROR_AMD) && (Category <= GL_DEBUG_CATEGORY_OTHER_AMD))
        return CategoryStrings[Category - GL_DEBUG_CATEGORY_API_ERROR_AMD];

    return "Unknown";
}








void GLVersionAndExtensions::ParseGLVersion()
{
    const char* version = (const char*)glGetString(GL_VERSION);
    int fields = 0, major = 0, minor = 0;
    bool isGLES = false;

    OVR_ASSERT(version);
    if (version)
    {
        OVR_DEBUG_LOG(("GL_VERSION: %s", (const char*)version));

        // Skip all leading non-digits before reading %d.
        // Example GL_VERSION strings:
        //   "1.5 ATI-1.4.18"
        //   "OpenGL ES-CM 3.2"
        OVR_DISABLE_MSVC_WARNING(4996) // "scanf may be unsafe"
        fields = sscanf(version, isdigit(*version) ? "%d.%d" : "%*[^0-9]%d.%d", &major, &minor);
        isGLES = (strstr(version, "OpenGL ES") != NULL);
        OVR_RESTORE_MSVC_WARNING()
    }
    else
    {
        LogText("Warning: GL_VERSION was NULL\n");
    }

    // If two fields were not found,
    if (fields != 2)
    {
        static_assert(sizeof(major) == sizeof(GLint), "type mis-match");

        glGetIntegerv(GL_MAJOR_VERSION, &major);
        glGetIntegerv(GL_MINOR_VERSION, &minor);
    }

    // Write version data
    MajorVersion = major;
    MinorVersion = minor;
    WholeVersion = (major * 100) + minor;
    IsGLES = isGLES;
    IsCoreProfile = (MajorVersion >= 3); // Until we get a better way to detect core profiles, we err on the conservative side and set to true if the version is >= 3.
}


bool GLVersionAndExtensions::HasGLExtension(const char* searchKey) const
{
    if (Extensions && Extensions[0]) // If we have an extension string to search for individual extensions...
    {
        const int searchKeyLen = (int)strlen(searchKey);
        const char* p = Extensions;

        for (;;)
        {
            p = strstr(p, searchKey);

            // If not found,
            if (p == NULL)
            {
                break;
            }

            // Only match full string
            if ((p == Extensions || p[-1] == ' ') &&
                (p[searchKeyLen] == '\0' || p[searchKeyLen] == ' '))
            {
                return true;
            }

            // Skip ahead
            p += searchKeyLen;
        }
    }
    else
    {
        if (MajorVersion >= 3) // If glGetIntegerv(GL_NUM_EXTENSIONS, ...) is supported...
        {
            GLint extensionCount = 0;
            glGetIntegerv(GL_NUM_EXTENSIONS, &extensionCount);
            GLenum err = glGetError();

            if (err == 0)
            {
                for (GLint i = 0; i != extensionCount; ++i)
                {
                    const char* extension = (const char*)glGetStringi(GL_EXTENSIONS, (GLuint)i);

                    if (extension) // glGetStringi returns NULL upon error.
                    {
                        if (strcmp(extension, searchKey) == 0)
                            return true;
                    }
                    else
                        break;
                }
            }
        }
    }

    return false;
}

void GLVersionAndExtensions::ParseGLExtensions()
{
    if (MajorVersion >= 3)
    {
        // Set to empty because we need to use glGetStringi to read extensions on recent OpenGL.
        Extensions = "";
    }
    else
    {
        const char* extensions = (const char*)glGetString(GL_EXTENSIONS);

        OVR_ASSERT(extensions);
        if (!extensions)
        {
            extensions = ""; // Note: glGetString() can return null
            LogText("Warning: GL_EXTENSIONS was NULL\n");
        }
        else
        {
            // Cannot print this to debug log: It's too long!
            //OVR_DEBUG_LOG(("GL_EXTENSIONS: %s", (const char*)extensions));
        }

        Extensions = extensions;
    }

    // To do: revise the code below to loop through calls to glGetStringi(GL_EXTENSIONS, ...) so that all extensions below 
    // can be searched with a single pass over the extensions instead of a full loop per HasGLExtensionCall. 

    if (MajorVersion >= 3)
    {
        SupportsVAO = true;
    }
    else
    {
        SupportsVAO =
            HasGLExtension("GL_ARB_vertex_array_object") ||
            HasGLExtension("GL_APPLE_vertex_array_object");
    }

    SupportsDrawBuffers = HasGLExtension("GL_EXT_draw_buffers2");

    // Add more extension checks here...
}

void GetGLVersionAndExtensions(GLVersionAndExtensions& versionInfo)
{
    versionInfo.ParseGLVersion();
    // GL Version must be parsed before parsing extensions:
    versionInfo.ParseGLExtensions();
    // To consider: Call to glGetStringi(GL_SHADING_LANGUAGE_VERSION, ...) check/validate the GLSL support.
}


}}} // namespace OVR::Render::GL