Hi folks,
I am really struggling with FBO’s on various ATI cards. Currently I am testing on a laptop with ATI X2300HD.
I am actually having a lot of different problems. One biggie is that it crashes immediately if I try to call glGenerateMipmapsEXT() on it. This has been the topic of lots of discussions here, none of the solutions posted have worked for me. Anyway, I have just given up on that at the moment and disabled mipmaps for FBO cards.
The issue this time is that I use FBO’s for render to texture, and some of the resulting textures become garbled (not all though…). This works perfectly on NVIDIA hardware on different platforms (we have tested on Linux, Windows and Mac), but not on ATI.
An example of the result can be seen here:
http://www.worldbeside.com/screenshots/fbo-error.jpg
Here is the FBO setup code:
// create objects
glGenFramebuffersEXT(1, &fb_); // Frame buffer object
glGenTextures(1, &handle_); // Texture handle
if(z_depth_ > 0)
glGenRenderbuffersEXT(1, &depth_rb_); // Render buffer for z buffering
Btk::logDebug("GngTools") << "GngFBOTexture::initBuffers(): handle = " << handle_ << Btk::endl;
// Make frame buffer active
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb_);
// Mipmap generation for FBO's on ATI just doesn't work :-(
if(GngGL::getVendor() == GngGL::VENDOR_ATI)
{
if(min_filter_ != GL_LINEAR && min_filter_ != GL_NEAREST)
min_filter_ = GL_LINEAR;
if(mag_filter_ != GL_LINEAR && mag_filter_ != GL_NEAREST)
mag_filter_ = GL_LINEAR;
}
// Initialize texture
glBindTexture(GL_TEXTURE_2D, handle_);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrap_s_);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrap_s_);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, mag_filter_);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, min_filter_);
if(min_filter_ != GL_NEAREST &&
min_filter_ != GL_LINEAR)
{
int mm_level = MtkTools::ilog2(std::min(width_, height_));
Btk::logDebug("GngTools") << "GngFBOTexture: Max mipmap level = " << mm_level << ", size = " << width_ << " x " << height_ << Btk::endl;
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, mm_level);
}
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width_, height_, 0, GL_RGB, GL_UNSIGNED_BYTE, (GLvoid*)NULL);
// Establish a mipmap chain
if(min_filter_ != GL_NEAREST &&
min_filter_ != GL_LINEAR)
{
Btk::logDebug("GngTools") << "GngFBOTexture: Enable automatic Mipmap generation" << Btk::endl;
#ifdef ATI_GENERATE_MIPMAP_HACK
if(GngGL::getVendor() == GngGL::VENDOR_ATI)
ctx->enable(GL_TEXTURE_2D); // Bug in many ATI drivers!
#endif
glGenerateMipmapEXT(GL_TEXTURE_2D);
}
// Attach texture to framebuffer color buffer
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, handle_, 0);
err_code = glGetError();
if (err_code != GL_NO_ERROR)
{
char* err_str = (char*)gluErrorString(err_code);
Btk::logError("GngTools") << "GngFBOTexture [2] GL error: " << err_str << Btk::endl;
}
// Initialize depth renderbuffer
if(z_depth_ > 0)
{
Btk::logDebug("GngTools") << "GngFBOTexture: Set up depth render buffer: z = " << z_depth_ << ", w = " << width_ << ", h = " << height_ << Btk::endl;
glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, depth_rb_);
GLenum depth_fmt = GL_DEPTH_COMPONENT16;
/*
if(z_depth_ == 16)
depth_fmt = GL_DEPTH_COMPONENT16;
else if(z_depth_ == 24)
depth_fmt = GL_DEPTH_COMPONENT24;
else if(z_depth_ == 32)
depth_fmt = GL_DEPTH_COMPONENT32;
*/
glRenderbufferStorageEXT(GL_RENDERBUFFER_EXT, depth_fmt, width_, height_);
err_code = glGetError();
if (err_code != GL_NO_ERROR)
{
char* err_str = (char*)gluErrorString(err_code);
Btk::logError("GngTools") << "GngFBOTexture [4] GL error: " << err_str << Btk::endl;
}
glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, depth_rb_);
}
bool result = checkFBOStatus();
// Set rendering to window
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, prev_fb_);
The FBO status is GL_FRAMEBUFFER_COMPLETE and no GL errors are detected after the setup.
When rendering to the texture, I do the following:
glPushAttrib(GL_VIEWPORT_BIT);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb_);
glViewport/modelview/projection
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
... render ...
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
glPopAttrib();
… and when applying the texture, simply:
glBindTexture(GL_TEXTURE_2D, handle_);
If anyone can help me with this I’d be extremely happy 
Cheers
