[1.0.29 and previous] Seeing behind the horizon

[Gez]

The map where I noticed this is the first of episode 2 of the Demon Eclipse. Just start a new game, select the "Pandemonium Fortress" episode, and it's just in front of you.

Basically, there are dummy sectors containing various monsters (imps, demons, cacos, plus the DECORATE bloodfiends and guardian cubes -- I've put a blue border around them on the pic) that are behind this Line_Horizon wall. And they are rendered, even though they shouldn't be.

Depending on the player's view pitch and height, their rendering is toggled on or off. The higher we are, the higher we look, the more likely the glitch will be there.

[Graf Zahl]

I don't know what to about this because it's caused by a limitation of the engine. The engine renders every sprite in all visible sectors and these sprites are in a sector that shares a part with the visible world.

[Nash]

Maybe you should just get Eriance to fix it by moving the monster cells away.

[Graf Zahl]

Or by reassigning a separate sector to them.

[Graf Zahl]

I finally, finally found the flaw in the logic that caused this glitch. No wonder that all previous attempts failed because they always tried to doctor the symptoms, not the cause.

Horizons are drawn without depth buffer so I use a simpler stencil setup that only initializes the stencil buffer without messing around with the depth buffer. But what I completely forgot to consider is that in this case there won't be a depth pass after rendering the horizon stuff. So the initial stencil pass must set the depth buffer which it did not. So everything behind the portal line bled through...

[Gez]

Great!