Bug 1020 - First MSAA FBO frame on a mac osx nvidia card not antialiased

OSX/Nvidia's FBO needs to be cleared before blitting,
otherwise first MSAA frame lacks antialiasing.

GLFBODrawableImpl.initialize(..) can clear
GL.GL_COLOR_BUFFER_BIT and GL.GL_DEPTH_BUFFER_BIT, if used.

FBObject cannot clear the buffer(s) due to it's low-level API,
i.e. it cannot know when the first bind occurs _after_ user
completed FBO setup (attaching buffers).

Hence plain FBObject usage required manual injection
of glClear(..) after setup as demonstrated in GLJPanel.

We may need to elaborate in this case,
i.e. add an FBObject API entry like 'fbo.postInitNotify()'.

2 files changed, 18 insertions, 2 deletions

diff --git a/src/jogl/classes/javax/media/opengl/awt/GLJPanel.java b/src/jogl/classes/javax/media/opengl/awt/GLJPanel.java
index e2ccc1097..cfb11a2b0 100644
--- a/src/jogl/classes/javax/media/opengl/awt/GLJPanel.java
+++ b/src/jogl/classes/javax/media/opengl/awt/GLJPanel.java
@@ -1636,6 +1636,11 @@ public class GLJPanel extends JPanel implements AWTGLAutoDrawable, WindowClosing
               helper.setAutoSwapBufferMode(false); // we handle swap-buffers, see handlesSwapBuffer()
 
               final GL gl = offscreenContext.getGL();
+              // Remedy for Bug 1020, i.e. OSX/Nvidia's FBO needs to be cleared before blitting,
+              // otherwise first MSAA frame lacks antialiasing.
+              // Clearing of FBO is performed within GLFBODrawableImpl.initialize(..):
+              //   gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
+
               final GLCapabilitiesImmutable chosenCaps = offscreenDrawable.getChosenGLCapabilities();
               final boolean glslCompliant = !offscreenContext.hasRendererQuirk(GLRendererQuirks.GLSLNonCompliant);
               final boolean useGLSLFlip = useGLSLFlip_pre && gl.isGL2ES2() && glslCompliant;
@@ -1653,6 +1658,7 @@ public class GLJPanel extends JPanel implements AWTGLAutoDrawable, WindowClosing
                       fboFlipped.reset(gl, fboDrawable.getSurfaceWidth(), fboDrawable.getSurfaceHeight(), 0, false);
                       fboFlipped.attachColorbuffer(gl, 0, chosenCaps.getAlphaBits()>0);
                       // fboFlipped.attachRenderbuffer(gl, Attachment.Type.DEPTH, 24);
+                      gl.glClear(GL.GL_COLOR_BUFFER_BIT); // Bug 1020 (see above), cannot do in FBObject due to unknown 'first bind' state.
                       glslTextureRaster = new GLSLTextureRaster(fboDrawable.getTextureUnit(), true);
                       glslTextureRaster.init(gl.getGL2ES2());
                       glslTextureRaster.reshape(gl.getGL2ES2(), 0, 0, fboDrawable.getSurfaceWidth(), fboDrawable.getSurfaceHeight());
diff --git a/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java b/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java
index a779fed3b..9694ca9a9 100644
--- a/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java
+++ b/src/jogl/classes/jogamp/opengl/GLFBODrawableImpl.java
@@ -60,9 +60,9 @@ public class GLFBODrawableImpl extends GLDrawableImpl implements GLFBODrawable {
     private int fboIBack;  // points to GL_BACK buffer
     private int fboIFront; // points to GL_FRONT buffer
     private int pendingFBOReset = -1;
-    /** Indicated whether the FBO is bound. */
+    /** Indicates whether the FBO is bound. */
     private boolean fboBound;
-    /** Indicated whether the FBO is swapped, resets to false after makeCurrent -> contextMadeCurrent. */
+    /** Indicates whether the FBO is swapped, resets to false after makeCurrent -> contextMadeCurrent. */
     private boolean fboSwapped;
 
     /** dump fboResetQuirk info only once pre ClassLoader and only in DEBUG mode */
@@ -189,7 +189,17 @@ public class GLFBODrawableImpl extends GLDrawableImpl implements GLFBODrawable {
                     fbos[i].setSamplingSink(ssink);
                     fbos[i].resetSamplingSink(gl); // validate
                 }
+                // Clear the framebuffer allowing defined state not exposing previous content.
+                // Also remedy for Bug 1020, i.e. OSX/Nvidia's FBO needs to be cleared before blitting,
+                // otherwise first MSAA frame lacks antialiasing.
+                fbos[i].bind(gl);
+                if( useDepth ) {
+                    gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
+                } else {
+                    gl.glClear(GL.GL_COLOR_BUFFER_BIT);
+                }
             }
+            fbos[fbosN-1].unbind(gl);
             fbos[0].formatToGLCapabilities(chosenFBOCaps);
             chosenFBOCaps.setDoubleBuffered( chosenFBOCaps.getDoubleBuffered() || samples > 0 );
         } else {