I am having a hell of a time generating mipmaps for my FBO texture. My mipmaps just aren't being generated properly. I render a grid to the FBO on every frame, and try to generate a full set of mipmaps immediately. Then I draw my FBO texture to the screen:
When I move the camera back from the render position, the grid disappears completely within my black quad. Obviously, the renderer is trying to use my mipmaps to render my quad to the screen, but those mipmap texture levels haven't been generated.
My FBO texture is 1024x1024. I'm using OpenGL Version 3.2 on an nVidia Quadro 4800 card, Windows 7.
Here is my code for creating my FBO:
texData.width = w;
texData.height = h;
texData.bFlipTexture = true;
texData.glType = GL_RGB;
this->autoClear = autoClear;
// create & setup texture
glGenTextures(1, (GLuint *)texData.textureName); // could be more then one, but for now, just one
glEnable(GL_TEXTURE_2D);
const GLubyte* ver = glGetString(GL_VERSION);
glBindTexture(GL_TEXTURE_2D, (GLuint)texData.textureName[0]);
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_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); //GL_LINEAR
//glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); // automatic mipmap - when I include this line and draw my texture
//at a small scale, I see the imagery, but it does not appear to be mipmapped -- it looks like a typical (jagged) linear shrinkage. (See image below)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8 , texData.tex_w, texData.tex_h, 0, /*texData.glType*/ GL_RGB, GL_UNSIGNED_BYTE, 0);
// when I use glGenerateMipmapEXT(), I see proper transitions between mipmap levels as I scale down my texture, but every mipmap level
//is just black with no imagery. (See image above.) Level 0 crossfades to black as it reaches a 50% scale.
glGenerateMipmapEXT(GL_TEXTURE_2D); //Allocate necessary space for mipmaps
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
// create & setup FBO
glGenFramebuffersEXT(1, &fbo);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
// attach it to the FBO so we can render to it
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, (GLuint)texData.textureName[0], 0);
glGenRenderbuffersEXT(1, &depthBuffer);
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depthBuffer);
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, GL_DEPTH_COMPONENT, texData.tex_w, texData.tex_h);
// Attach the depth render buffer to the FBO as it's depth attachment
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depthBuffer);
GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
if(status != GL_FRAMEBUFFER_COMPLETE_EXT) {
cout<<"glBufferTexture failed to initialize. Perhaps your graphics card doesnt support the framebuffer extension? If you are running osx prior to system 10.5, that could be the cause"<<endl;
std::exit(1);
}
In the code above, you may notice the commented line in which I set:
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
...if I use this call instead of glGenerateMipmapEXT(), then I can see my entire FBO texture rendered in my quad, but it is obviously NOT mipmapped:
Anyway, when it's time to actually render to my FBO texture, here is my pseudocode:
glBindTexture(GL_TEXTURE_2D, 0);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
//DRAW to FBO
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0); //unbind the FBO
glBindTexture(GL_TEXTURE_2D, (GLuint)texData.textureName);
//glEnable(GL_TEXTURE_2D); //I'm told I need this on an ATI card, but not necessary for nVidia?
glGenerateMipmapEXT(GL_TEXTURE_2D);
I have tried lots of combinations of tiny tweaks to the different calls, especially glTexImage2D, but haven't gotten anywhere. I've tried to mimic every example usage of glGenerateMipmapEXT() I can find online. I'd rather not deal with gluBuild2DMipmaps(), and I don't know why it should work where these other methods fail. Please help! I've been stuck on this for two days!
