Sector portal can be rendered on lines

[Fishytza]

Tested with GZDoom 3.3.0 64-bit
Both software and hardware renderer.

I'm reporting this because I cannot tell if this is undefined behavior or intentional.

Similar to the old sky hack, a sector portal can bleed onto a two-sided line that has no upper/lower texture, and the sector where the portal is in use is higher/lower than its neighbor which has no portal.

sector-portal-on-line-test.wad

In this test map the gravity has been lowered so it's easy to jump through the portals. And even though the portals are being rendered on the lines as well, they are purely solid.

They are rendered all the time without a hitch in the hardware renderer.
In software, the upper one turns into a HOM effect when you jump up (not through the portal) while the lower one behind your start position is a HOM until you jump.

[Graf Zahl]

Missing textures in unexpected places are always undefined behavior. The portals and skies share a lot of the same logic so this is not surprising.

[Fishytza]

So I take it I shouldn't be doing this?

[Marisa the Magician]

I'd assume if this doesn't break anything it could just be a "bug ascended to feature". Does it work on all renderers?

[Graf Zahl]

This won't work as a feature because portal content gets clipped by the portal plane so it may glitch. If this gets done properly it will be done like in Eternity where the portal on the wall must be set explicitly.

[Gez]

In software, the upper one turns into a HOM effect when you jump up (not through the portal) while the lower one behind your start position is a HOM until you jump.

So I take it I shouldn't be doing this?

Undefined behavior that doesn't work in one of the renderers is best avoided, yes.

[Graf Zahl]

It should be noted that sector portals are very, very limited in the software renderer so that's no indicator here.