Getting vertex-shader transformed geometry back from the gpu in OpenGL

Question

I would like to generate vertex geometry on the cpu and then pass it to the GPU and run a number of vertex shaders on the vertices and then get these transformed vertices back to the cpu. I dont want to render the vertices or run any fragment shaders.

Is it possible to get the vertex-shader transformed vertices back from the gpu onto the cpu? If so how?

Answer 1

Yes, the facility required is called "Transform Feedback Buffers". Extension to OpenGL-2 http://www.opengl.org/registry/specs/ARB/transform_feedback2.txt

Introduced to being official OpenGL functionality with OpenGL-3.0