I tried to implement transform feedback in my app, but I seem to be stuck in a seemingly weird situation (or stupid bug).
I want to record the GL_POSITION, without rasterizing.
The problem is :
If I use a vertex shader, hell breaks loose, numbers are whacko.
If I use fixed function for vertex shader, or fixed function for both vs & fs, everything is allright.
The shader I tried is the most minimalistic possible
( void main() {gl_Position = ftransform();} ). If a make a shader with the most minimal fs, and no vs ( to use fixed func ), then it works ok.
As always, ensure your transform feedback VBOs are large enough to hold the results.
Oddly enough, I’ve sometimes needed to clear the color buffer before using transform feedback, or else I get odd results when resizing the window (even though I’m not rasterizing).
The glTransformFeedbackAttribsNV() function is only to be used with fixed function (or assembly shaders, as I just discovered from the specification). Try using glTransformFeedbackVaryingsNV() with a shader.