glViewport(0, 0, width, height);
glDisable(GL_BLEND);
glEnable(GL_DEPTH_TEST);
+ glDepthMask(GL_TRUE);
glDepthFunc(GL_LESS); // We store the difference between I_0 and I_1, where less difference is good. (Default 1.0 is effectively +inf, which always loses.)
fbos.render_to(depth_rb, flow_tex);