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Hi,

I want to run custom vertex shaders (on the GPU) to perform stream reduction on a data set, reading back the results to main memory buffers.

1. I set up a set of texture/vertex buffers for the input to the custom shaders.

2. I call them, they do their thing and output to other texture/vertex buffers.

Question is, how do I read back the contents of the modified texture/vertex buffer after the shader has finished?

I'm pretty sure this is possible with DirectX (it is with OpenGL anyway), so is there a way to do this with Dark GDK/Physics calls, or do I need to go to the DirectX API directly?

As an asside, what are the implications of using the DirectX API directly along side Dark GDK/Physics/Lights etc...?

Regards, Dan...

After some more reading, it looks like it's not possible to create a custom Vertex/Texture/Constant buffer in DirectX 9 that is in video memory and can be read back (readable) from the CPU side of things.

I.e. "Steam out" is a new feaure in DirectX 10.

I see that DirectX 10 is at release candidate stage for Windows XP, are there any plans/roadmap for integrating Dark GDK/Physics/Lights etc... with DirectX 10?

There may be an alternative, but this is just an idea at the moment... Is it possible to use CUDA at the same time as DirectX 9? I.e. could I use Dark GDK/Physics/Lights etc and at the same time also use the same video card for CUDA processing?

If this is the way the industry is going, "Stream Out" is going to be an essential tool for next generation games, so DirectX 10 support in Dark GDK would be highly desirable.

Regards, Dan...

Aparently you can render to texture buffers in DX9 HLSL and read the data back, so I might be able to pull this off after all.