CODEWITHSUNDEEP
opengltextures
user46759
user46759

Reputation: 15

Read back data stored in a texture

I have got a texture which is updated from a fragment shader that calculates points positions.

What is the good way to read it back so it could be drawn as primitives ?

Upvotes: 1

Views: 352

Answers (1)

jozxyqk
jozxyqk

Reputation: 17396

If you want to draw using the data from the texture, reading back to host memory is a waste and slow (But for reference you could use glGetTexImage or glReadPixels).

  • Instead, you can draw primitives without providing vertex positions and read them from your texture in the vertex shader (bound as a sampler and using texelFetch for example).

    The coordinates for texel fetch can come from a per-vertex attribute (just like regular texture coordinates), or you can use gl_VertexID to calculate them implicitly.

  • As @ColonelThirtyTwo said, you can also use transform feedback. Not using your texture and doing the computation in the fragment shader, but replacing it with computation in a vertex shader. Here the varying variables normally interpolated to the fragment shader get packed and saved in a buffer, still on the GPU.

Upvotes: 1

Related Questions