Impossible Portal Trick

[Xaser]

Hey all,

I'm in a pickle as far as mapping is concerned. I could've sworn this was doable at some point, but I can't figure out how the bloody hell to do this using a certain feature.

Here's the basic setup:


Basically, I've got a short "gazebo" thing that's made to look 3D via the age-old "lowered sky" trick (see 1st panel). Trouble is, I'm adding some buildings to the outlying areas, and these can appear cut-off if you view them from the other side of the gazebo (an effect I call "sky clipping"). I'd like to avoid this by using portals, but is there any way to portal only the lowered sky (as shown in the 2nd panel) and get it to work? Chopping the entire area in half (e.g. 3rd panel) is pretty much a non-option given the complexity of the neighboring outdoor area, and it's something I want to avoid at all costs. Also, I realize you can't have wall portals in ZDoom, but I've been unable to do this with slopes either because of the fact that Sector_SetPortal is one-way, making the inner slope in the portal sector still appear.

Anyone think they can lend a hand in making this work? Here it is in wad form, with a placeholder portal that (obviously) doesn't work. If someone can figure out how to get it to work without slicing the entire area in half horizontally, you'd be my hero. Or something equally cheesy.

Another catch: this is for Hacx, so I can't use portal things (which might actually solve the problem easily since they're two-way), since it also needs to be compatible with EE, which has a version of Sector_SetPortal that works well cross-port.

Also, before someone asks "why on Earth did you set it up that way?", don't ask me, ask Stephen Watson, the original author of this particular Hacx map.

Anyone have any advice? I'm a stump.

[alysiumX]

Took a look at that map, I believe portals work by looking into sectors to see geometry, due to this it seems like it would be impossible to see through. However, you can use the new 2.60 zdoom to use 3d floor to accomplish this effect

[Nash]

Pretty sure he's avoiding 3-d floors to maintain EE compatibility.

[Xaser]

As an update of sorts, I actually managed to figure this out, sorta. Not quite the solution I had in mind, but I was able to get it working with minimal copy+pasting, hence the recent portal screens in that other thread.

Thanks anyhow, though. Took me long enough to realize that the trouble is that ZDoom just doesn't like recursive portals yet.

[Graf Zahl]

What you mark 'trying to avoid' is the only decent way to prevent GZDoom from puking all over it. Any setup that has the view traverse from the main area through a portal to another part of the main area are an absolute no-go. Allowing these would hang the engine with little chance to avoid it.

[printz]

So using portals is really like fabricating multiple layers using different masks... Nice.

[Xaser]

What you mark 'trying to avoid' is the only decent way to prevent GZDoom from puking all over it. Any setup that has the view traverse from the main area through a portal to another part of the main area are an absolute no-go. Allowing these would hang the engine with little chance to avoid it.

The software renderer exhibits this trouble as well, at least to some extent. When trying to set up that very thing, in the few cases where it did attempt to render recursively, the framerate dropped to near-unplayable levels.

What I ended up doing is a "halfway point" between the two in which I copied over the vista buildings into the portal sector and skipped the split-everything-in-the-old-area-in-half part. The net effect is that you get what you see in these shots with the fun bit of trivia that the portion of the distant building you see above the building is actually an entirely different set of lines than the lower half. Not that you can tell if they're identically positioned, of course.

The good part is that ZDoom, GZDoom, and Eternity all render it the same. Crisis averted.

[Graf Zahl]

The software renderer exhibits this trouble as well, at least to some extent. When trying to set up that very thing, in the few cases where it did attempt to render recursively, the framerate dropped to near-unplayable levels.

Yeah, same cause. The only difference being that the software renderer has more precise clipping information to avoid an infinite recursion. GZDoom can't really decide if a portal needs to be rendered or not so I did it the hard way and don't allow any recursions.

(Anyway, nice to see that someone actually tries to make maps that work with both ZDoom and Eternity while using some of their shared enhanced features.)

[Xaser]

Anyway, nice to see that someone actually tries to make maps that work with both ZDoom and Eternity while using some of their shared enhanced features.

The tricky part is the actor definitions, since everything needs to be done twice. The idea, though, is to have a nice editing featurebase for Hacx set up so that anyone can come in and easily make maps for it that work in both engines.