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silvermace

Float PBuffers, CG and an ATI card.

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So i've created a floating point 128bit PBuffer (FPB), i've rendered my scene to the PBuffer, and i've sent it down to the CG fragment shader. Questions: 1. Can i use tex2D(...) as normal, will this work for ATI hardware? 2. Are there any special things i need to watch out for when using FPB in CG with ATI hardware? 3. Are there any examples availible of FPB+Cg+ATI action? Cheers, Danu EDIT: my Machine specs: VS 7.1, WinXP SP2, Radeon 9500 Pro, Cat 4.7's, 512 MB ram, P4-3.0 [Edited by - silvermace on September 26, 2004 5:08:47 AM]

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One thing to watch out for: alpha blending does not seem to work properly on float targets, it runs very very slowly - when I tried it on my X800 Pro it dropped to literally 1/100th the speed. I doubt that a 9500 is any better at it.

It may be only certain blending modes that aren't well supported, haven't messed with it enough to find out.

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Quote:
Original post by uavfun
One thing to watch out for: alpha blending does not seem to work properly on float targets, it runs very very slowly - when I tried it on my X800 Pro it dropped to literally 1/100th the speed. I doubt that a 9500 is any better at it.

It may be only certain blending modes that aren't well supported, haven't messed with it enough to find out.

Geforce 6800 is the only card that supports floating-point blending.. :/

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hm, so im wondering how to do my HDR rendering if i cant do
floating point blending...

rendering the HDR blurred image over the current scene, but
how if i cant do alpha blending?

i just realised i have no idea HOW to do alpha blending in Cg
any tips/sample code?

Cheers,
Danu

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Cg does vertex and fragment processing, not (per se) other parts of the pipeline, like vertex fetch, triangle set-up, depth test or framebuffer blending. Now, there is the CGFX format which is very similar to the D3D .FX file format, which allows you to specify techniques, passes, and render states (such as blending), but I know people who have had trouble trying to make that work well on GL.

Typically, when you do HDR effects, you render to a buffer, which you then bind (or copy) to a texture, and render to another buffer, texturing out of the first texture where the "previous color value" is needed.

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im really kind of lost with the whole process, do i need to
find the average luminiance value and all that stuff?

is that the only way to do HDR in realtime?

all the demo's on the net don't do any generation as such
rather they use already generated HDR images to do the rendering
in realtime, have you implemented some (usfull) HDR in OpenGL?

/gets back to work on HDR demo

Cheers,
Danu

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