Hello again,
I hope people will indulge me in my idiocy a bit longer on this forum as I'm having a bit of trouble getting the "OpenGL Frame Buffer Object 101" to work properly... Basically I'm trying to render the images to a depth buffer in the hopes of achieving a higher color resolution. I read somewhere that pixels rendered to the color buffer are all clamped and to 0-255 values where as the same is not true for example the depth buffer...? Perhaps I am wrong in this assumption? Anyways - I am hoping someone has the time to glance at some of my code and see if they can spot anything out of order...
Just to get something out of of the way - If I do NOT render to the FBO object - i.e call "" before rendering, I get a pretty blue/white rotating wierd triangle.
Some initialization code
gpuAiVertexProgram = cgCreateProgramFromFile(gpuAiContext,
CG_SOURCE,
"testShader.cg",
gpuAiVertexProfile,
"main",
NULL);
if(gpuAiVertexProgram != NULL)
{
/* Vertex shader only needs to be loaded once */
cgGLLoadProgram(gpuAiVertexProgram);
/* Bind parameters to give access to variables in the shader */
//KdParam = cgGetNamedParameter(VertexProgram, "Kd");
ModelViewProjParam = cgGetNamedParameter(gpuAiVertexProgram, "ModelViewProj");
ModelViewProjITParam = cgGetNamedParameter(gpuAiVertexProgram, "ModelViewProjIT");
//VertexColorParam = cgGetNamedParameter(VertexProgram, "IN.VertexColor");
}
// Generate Frame buffer so we can use it!
glGenFramebuffersEXT(1, &fbo); // Get a handle
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo); // GL_FRAMEBUFFER_EXT is apparently the only bindable destination right now.
// Generate a Renderbuffer for the FBO
glGenRenderbuffersEXT(1, &depthbuffer); // Get a handle
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, 512, 512); // Define storage space for the renderbuffer
// Generate a texture
glGenTextures(1, &img);
glBindTexture(GL_TEXTURE_2D, img);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, 512, 512, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
// Attach function FBO<->Renderbuffer
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depthbuffer);
// Attach function FBO<->Texture
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, img, 0);
if (checkFramebufferStatus()) {
printf("Successfully attached FBO to Depthbuffer! \n");
} else {
exit(-3);
}
The display code...
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glPushMatrix();
glRotatef(angle,0.0,1.0,0.0);
if (enableCG) {
cgGLBindProgram(gpuAiVertexProgram);
if(ModelViewProjParam != NULL)
cgGLSetStateMatrixParameter(ModelViewProjParam, CG_GL_MODELVIEW_PROJECTION_MATRIX,
CG_GL_MATRIX_IDENTITY);
if(ModelViewProjITParam != NULL)
cgGLSetStateMatrixParameter(ModelViewProjITParam,
CG_GL_MODELVIEW_MATRIX,
CG_GL_MATRIX_INVERSE_TRANSPOSE);
cgGLEnableProfile(gpuAiVertexProfile);
}
glPushAttrib(GL_VIEWPORT_BIT);
glViewport(0,0,512, 512);
glBegin(GL_TRIANGLE_STRIP);
{
glVertex3f(-0.8,-0.8,0.0);
glVertex3f(0.8,-0.8,0.0);
glVertex3f(0.0,0.8,0.0);
//glVertex3f(-0.8f, 0.8f, -114.0f);
//glVertex3f(-0.7f, 0.8f, -114.0f);
//glVertex3f(-0.75f, 0.9f, -114.0f);
glVertex3f(-0.65f, 0.9f, 2.0f);
//glVertex3f(-0.6f, 0.8f, -114.0f);
}
glEnd();
glPopAttrib();
if (enableCG) {
cgGLDisableProfile(gpuAiVertexProfile);
}
glPopMatrix();
// swapping the buffers causes the rendering above to be
// shown
glutSwapBuffers();
// finally increase the angle for the next frame
angle++;
glFlush();
I'm using imdebug (which is a small tool to read an image into an extra tool and then look closer at it) to peer into the various buffers and have a look at whats inside. Here are the calls I use... The odd thing is... If I use imdebug to read from the screen it works fine when I render to it, but also when rendering to the depth buffer is active (or should be) - only then I see the blue triangle basically overwriting itself creating lots of layers of itself... Hmmm perhaps that needs clarification...
switch(key) {
case GLUT_KEY_F1 :
if (enableCG) {
enableCG = false;
printf("Cg Disabled...\n");
} else {
enableCG = true;
printf("Cg Enabled...\n");
}
break;
case GLUT_KEY_F2 :
if (rendertoBF) {
rendertoBF = false;
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
} else {
rendertoBF = true;
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
}
break;
case GLUT_KEY_F3 :
// Try to use imdebug to display whats in the texture attached to the depthbuffer
imdebug("rgba w=%d h=%d %p", 512, 512, &img);
break;
case GLUT_KEY_F4 :
// Try to use imdebug to render directly from the depth buffer
imdebugDepth(0,0,512,512);
break;
case GLUT_KEY_F5 :
printf("Read pixel from screen (color buffer?) into imdebug");
imdebugPixels(0,0,512,512,GL_RGBA);
break;
}
Any and all answers are much appreciated!
Regards,
Gazoo
