How To Do a Transform Feedback on Vertex Shader

Help & Support
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1

I need to read Shader Updated data in CPU, I guess its possible to do this with Transform Feedback, how to do a Transform Feedback on Vertex Shader or Fragment Shader , or Just somehow read Shader Updated data on CPU

2

I’m not sure WebGL supports ready GPU vertex buffer data back to CPU.
I think your better option would be to store data in a texture, and use fragment shader to process them to another texture, and download that.

3

Thank you very much for your reply. I’ve been stuck on this for two days now.

If possible, could you please briefly describe how I can do it?

Edit:
like this ?

https://playcanvas.vercel.app/#/graphics/multi-render-targets

and this ?

https://playcanvas.vercel.app/#/graphics/render-to-texture

4

I’ve done similar stand alone example before, so something like that.
1.zip (225.5 KB)

This loads the textures (your input data), processes them using a shader to a different texture. We just need to download it, not part of this example.

5

Thank you so much! I will check it out.

6

Had meeting, back now. This is not the simplest code, it generates the shader based on the number of textures for example, to prototype a generic texture layers processing tool in a way. But the idea is there. Write a custom shader and do it. Allocate texture with 32bit floats instead of 8bit and similar. Even MRT if you need to output more data.

7

yes but in my cause it will be little hard or Impossible to do that, I’m making a water shader and I need to get the water height using local coord of water entity so I switch to texture approach, but still cant get the correct height