Hi @all,
I have a few questions about the possibilities in shader programming.
Is it possible to write more than one RGBA-value to the frame buffer by a fragment program?
Can the result of any computation be written to a texture from within a shader?
What does multipass rendering look like? I’ve read about it very often but I don’t know what that means. Does that mean that the whole scene is rendered several times with the last result as an input oder is a for-loop also a kind of multipass?
I’m writing al little thesis about raytracing on programmable graphics hardware and these topics were mentioned as requisites.
Thanks for your time.
jlukas
>> Is it possible to write more than one RGBA-value to the frame buffer by a fragment program?
It’s possible on the latest generation of graphics cards, like the GF6800 by using the multiple render target (MRT) extension
>> Can the result of any computation be written to a texture from within a shader?
No, you’ll have to do a multipass algorithm by using copytex(sub)image or render to texture
>> What does multipass rendering look like? I’ve read about it very often but I don’t know what that means. Does that mean that the whole scene is rendered several times with the last result as an input oder is a for-loop also a kind of multipass?
In practice, with multipass rendering you draw the same geometry multiple times with different functionality. eg. a diffuse pass, a specular pass, gloss map, etc. Many passes can be combined to a single pass with multitexturing. Sometimes 2d post processing is also referred to as multipass.
>> I’m writing al little thesis about raytracing on programmable graphics hardware and these topics were mentioned as requisites.
Here are some usefull links:
A small FX composer raytrace application
http://download.nvidia.com/developer/SDK/Individual_Samples/MEDIA/HLSL/scene_raytrace.fx
A dissertation about ray tracing on a stream processor:
http://graphics.stanford.edu/papers/tpurcell_thesis/
Greetz,
Nico
Thanx that helps.
Chao
jlukas
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