GL_EXT_depth_bounds_test http://www.nvidia.com/dev_content/nvopenglspecs/GL_EXT_depth_bounds_test.txt GL_EXT_depth_bounds_test GL_DEPTH_BOUNDS_TEST_EXT 0x8890 GL_DEPTH_BOUNDS_EXT 0x8891 void glDepthBoundsEXT (GLclampd zmin, GLclampd zmax)