Wall portal discussion

There's a looming problem with wall portals in Eternity. As you know, walkable lines can be skipped by ultra-fast running things, most notably projectiles (monster projectiles under -fast are the most likely due to technical details)! With wall portals this looks much worse and game-breaking than classic W* linedef specials.

A solution to this would be replacing the "thing crosses line" trigger with a "thing enters sector", which is much more stable (much easier for an ultra-fast thing to hit a sector than a line). The sector through which it enters is most likely the one behind the line. Unfortunately, this may break existing maps (works in progress, if not even released ones!) where multiple different line portals, pointing to separate areas, share the same sector behind them. Of course, maybe I can apply a partitioning of sectors behind linedefs if this happens…

Are you fine with this?

Doesn't sound like a problem.

And what it never enters the sector? If it can pass the portal line without the hit being detected it may just as easily escape through one of the back walls - even in the same movement step.

Try to avoid it as much as you want to - I think the only robust solution for fast moving projectiles that doesn't result in a mess is to split up the move into smaller parts so that it can't miss the line.

Graf Zahl said:

I think the only robust solution for fast moving projectiles that doesn't result in a mess is to split up the move into smaller parts so that it can't miss the line.

I guess I can make a case for overly long distances where line portals (and only they) will be checked in interpolated positions as needed, while the rest of the "buggy" Doom behavior is preserved (i.e. not handled, so classic linedef walk-over actions can still be skipped).

printz said:

while the rest of the "buggy" Doom behavior is preserved

I can understand why this needs to be preserved for old maps, but I really don't understand why preservation of these things is so important that it gets in the way of one of the engine's main features.

I can see how this may be a problem with the player and wallrunning - no idea if a fast player can skip over the portal line, but for projectiles at least I wouldn't really expect any problems. They never slide along walls and they rarely interact with linedef triggers.

But well, looks like you are caught between a rock and a hard place here. Either you fix it and compromise one of Doom's most famous glitches or you preserve the glitch and compromise the portals...

If possible, it'd probably make the most sense to toggle that sort of behavior on and off globally based on whether or not a map uses portals, similarly to how the 3D thing clipping compatibility flag is auto-enabled on maps containing portals.