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Author:  obsidian [ 06-14-2008 03:45 PM ]
Post subject:  Antiportal

I was wondering if anyone who has had some luck using antiportals can shed some light on the proper use of them. I've been trying for a while to figure out the finer details of how they work, but I keep getting HoM in one place or another. Raven has been a big help by sending me some docs and pictures to look at, but I still can't see to figure out exactly how to place them.

Here's a test map that I've been working on. Stick it in your maps directory and compile. If you can figure out the right placement of the antiportal brushes, I'll be grateful.


Raven wrote:

Quick definition: An antiportal brush acts like both a hint brush and an areaportal brush mashed into one single entity. Unlike areaportals, antiportals are not restricted to the inside of door brushes. Unlike hint brushes, antiportals do not create VIS splits and add to the visdata size.

Antiportal restrictions:
  • Antiportals cannot be lined up with structural brushes or the default 1024X1024 engine splits or they will cause a leak in your level. This is because they are like a void to existing portals and will devour them causing a tear in the level's hull. They can be lined up with detail brushes.
  • Antiportals cannot be visible in playable space or they will give you the nasty HOM effect. You must bury the antiportal faces of the brush inside of detail and/or structural brushes.

Uses and other information:
  • You always use the skip texture in conjunction with the antiportal texture. Only one face of a brush needs to have the antiportal texture. The rest should have the skip texture.
  • Antiportals are easiest explained by trying to think of an Areaportal and a Hint brush all in one without a great deal of the downfalls.
  • Antiportals are best used in terrain maps, where a designer is trying to find ways to have VIS blockage in between terrain sections.
    • A structural brush (caulk or sky) that is jammed into the terrain and lifted to just under the top of the terrain or to the ceiling in the case of a skybox brush adds to the visdata size. This in turn can result in adding bulk to the .bsp file.
    • A well placed antiportal brush can be used to create the same VIS blocking wall in a specific terrain piece. The benefit over structural brushes comes in the form of no extraneous VIS splits. Using structural brushes and/or hint brushes to block VIS creates VIS splits and increases the .bsp file size. Antiportals do not cause VIS splits, yet they give you the same VIS blocking effect that hint and/or structural brushes give you.

Also, I suppose by "cannot be lined up with structural brushes...", it means that they can't be coplanar? But I assume they can be tangent.

Author:  wattro [ 06-15-2008 12:01 AM ]
Post subject:  Re: Antiportal

i can't help, but i do have a question...

isn't it a bit odd to put an antiportal inside of a structural brush? won't it get tossed away?

Author:  wattro [ 06-15-2008 12:07 AM ]
Post subject:  Re: Antiportal

does this help?


edit: what if you just put it across the whole map as one brush, splitting the area down the middle? Or it seems like it should go inside of other geometry or in the void to block other zones from showing up

Author:  obsidian [ 06-15-2008 07:15 AM ]
Post subject:  Re: Antiportal

No, Unreal antiportals work fairly different than Q3. Same idea of sorts, trying to achieve the same thing, but the Unreal ones are newer technology and more elegant. Q3 antiportals are sort of a mashup of the existing portaling technology that was added after the fact without modifying the engine.

Q3 antiportals are supposed to create a bsp split and then hide everything beyond it. The tricky thing is to get it to do that in a way that the player doesn't notice.

I'd post up the original stuff Raven sent me, but I'm not sure about the rights to that stuff since it was documentation from work.

Author:  wattro [ 06-15-2008 01:54 PM ]
Post subject:  Re: Antiportal

right, so assuming you have a large terrain map with... say... a mountain in the middle... you would put the antiportal inside the mountain to prevent things behind the antiportal (from the player's pov) from being drawn. the advantage is there is no vis split, but it also improves performance.

i think it works like a vis curtain if i am not mistaken. (anything behind the curtain is not drawn/seen)

though i am purely speculating as i haven't fired up radiant or tested anything for eons.

i would guess with your map (ok, i did fire up radiant) that you would want the areaportal to be embedded within the detail brushes, but not into any visible space.

edit: i ain't tech, but it looks like your map *should* do the trick

Author:  Raven [ 09-29-2008 08:35 AM ]
Post subject:  Re: Antiportal

Ydnar made these for very specific reasons and they are a bit touchy. If you lined the antiportal up with any structural splits or the 1024X1024 grid splits it will HOM. You have to make sure it is not lined up with any structural splits already in the map.

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