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SteveDeFacto

How to set back buffer format?

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[quote name='Brother Bob' timestamp='1313447573' post='4849600']
The back buffer has the same format as the front buffer. If you need a buffer with an arbitrary format, then you need to look into offscreen framebuffer objects.
[/quote]

That's actually the reason I need to do this. I'm using a framebuffer to render my effects but I need multi-sampling and I have to use OpenGL 3.1 which does not support multi sampled textures.(Ironically GL 3.2 does)The only thing I could think to do was draw to the back buffer with multi sampling and then copy it to a texture. This works great but the one flaw with this is that the back buffer is not a floating point texture which prevents me from using HDR effects...

I think what I need to do is create my frame buffer like this:


[code]
glGenFramebuffers(1, &rendertarget->frameBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, rendertarget->frameBuffer);

//// Multi sample colorbuffer
glGenRenderbuffers(1, &rendertarget->colorBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, rendertarget->colorBuffer);
glRenderbufferStorageMultisample(GL_RENDERBUFFER, 4, GL_RGBA16F, WindowRect.right - WindowRect.left, WindowRect.bottom - WindowRect.top);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, rendertarget->colorBuffer);

// Multi sample depth buffer
glGenRenderbuffers(1, &rendertarget->depthBuffer);
glBindRenderbuffer(GL_RENDERBUFFER, rendertarget->depthBuffer);
glRenderbufferStorageMultisample(GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT24, WindowRect.right - WindowRect.left, WindowRect.bottom - WindowRect.top);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, rendertarget->depthBuffer);[/code]


Then I bind the buffer, render to it, then copy the texture information from the frame buffer to a texture. Is that right? If so then how do I copy the frame buffer to a texture without binding a texture to the frame buffer?

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You can get the supported formats with DescribePixelFormat or use the the modern version which I can't remember off the top of my head. Check out the functions for FSAA.
Normally, the backhuffer doesn't support floating point formats.

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