From BlenderWiki
Feedback
These functions will transform a coordinate using the parameters stored by the appropriate state latching and matrix functions.
Header File: GPU_matrix.h
void GPU_freeback_vertex_3fv(GLenum type, GLfloat x, GLfloat y, GLfloat z, GLfloat out[3]); void GPU_freeback_vertex_4fv(GLenum type, GLfloat x, GLfloat y, GLfloat z, GLfloat w, GLfloat out[4]);
Header File: GPU_state_latch.h
GLfloat GPU_feedback_depth_range(GLfloat z); void GPU_freeback_viewport_2fv(GLfloat x, GLfloat y, GLfloat out[2]);