OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Configuring Transform Feedback Varyings

While the buffer bindings used for transform feedback are associated with a transform feedback object, the configuration of which outputs of the vertex (or geometry) shader are to be recorded into those buffers is stored in the active program object. To specify which varyings will be recorded during transform feedback, call:

void glTransformFeedbackVaryings(GLuint program,                         GLsizei count,                         const GLchar ** varyings,                         GLenum bufferMode);

Sets the varyings to be recorded by transform feedback for the program specified by program. count specifies the number of strings contained in the array varyings, which contains the names of the varyings ...