// This is the Vertex Shader for three dimensional polka dots.
//
// author(s): Joshua Doss
//
// Copyright (C) 2002-2004 3Dlabs Inc. Ltd.
//Create uniform variables for lighting to allow user interaction
//uniform float SpecularContribution;
//uniform vec3 LightPosition;
const float SpecularContribution = 0.36;
const vec3 LightPosition = vec3 (0, 4, 5);
varying vec3 MCPosition;
varying float LightIntensity;
void main(void)
{
float diffusecontribution = 1.0 - SpecularContribution;
// compute the vertex position in eye coordinates
vec3 ecPosition = vec3(gl_ModelViewMatrix * gl_Vertex);
// compute the transformed normal
vec3 tnorm = normalize(gl_NormalMatrix * gl_Normal);
// compute a vector from the model to the light position
vec3 lightVec = normalize(LightPosition - ecPosition);
// compute the reflection vector
vec3 reflectVec = reflect(-lightVec, tnorm);
// compute a unit vector in direction of viewing position
vec3 viewVec = normalize(-ecPosition);
// calculate amount of diffuse light based on normal and light angle
float diffuse = max(dot(lightVec, tnorm), 0.0);
float spec = 0.0;
// if there is diffuse lighting, calculate specular
if(diffuse > 0.0)
{
spec = max(dot(reflectVec, viewVec), 0.0);
spec = pow(spec, 16.0);
}
// add up the light sources, since this is a varying (global) it will pass to frag shader
LightIntensity = diffusecontribution * diffuse * 1.5 +
SpecularContribution * spec;
// the varying variable MCPosition will be used by the fragment shader to determine where
// in model space the current pixel is
MCPosition = vec3 (gl_Vertex);
// send vertex information
gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
}
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