Question

I am drawing a cube and a line grid in 3D in OpenGL:

glBegin(GL_QUADS);
...
glEnd();

glBegin(GL_LINES);
...
glEnd();

Now, independent of the order (if I draw the lines first or the quads first) and independent of the position it always happens that the lines are draw over the cube. I thought OpenGL draws front to back.

What I tried is to use:

glEnable(GL_BLEND);
glBlendFunc (GL_ONE, GL_ONE);

which does work but part of the cube is transparent now.
I also tried glDepthFunc(GL_NEVER) with disabling glEnable (GL_DEPTH_TEST) but I get the same problem that the cube appears transparent.

Does anyone have a hint to overcome this problem?

Answer 1

If you want to draw the lines in the background, just draw them (and the rest of the background) first, clear the depth buffer, then render the rest of the scene.

Or you can just give the lines a depth such that they will always be behind everything else, but then you have to make sure that none of your gameworld objects go behind it.