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Topic Starter Topic: -skyfix vs culling
RojaN Returned
Trainee
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Joined: 25 May 2016
Posts: 41
PostPosted: 07-08-2019 04:18 PM           Profile Send private message  E-mail  Edit post Reply with quote


Hello all, I have made a curious discovery.

While optimizing a map I noticed that when running Quake 3 Arena with r_showtris 1, There was no culling happening, either from occlusion or my areaportals. Every goldarned triangle was drawing.

After much experimentation, I narrowed it down to the -skyfix command while building (I had it after -meta but before vis). Removal of this item from bsp allowed sections of the map to be culled. Some of my areaportals even worked!

I'm on GTK Radiant 1.6.6, a recent switch. I tried building with the q3map2 from 1.6.5 and this seemed to improve culling with -skyfix slightly, but still much worse than without -skyfix.

For now, I'm just building without. Any thought as to why this might happen?
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dONKEY
The Afflicted
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Joined: 14 Oct 2001
Posts: 579
PostPosted: 07-08-2019 08:47 PM           Profile Send private message  E-mail  Edit post Reply with quote


Why are you using area portals?
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ToKu
Warrior
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Joined: 19 Sep 2012
Posts: 79
PostPosted: 07-09-2019 06:14 PM           Profile Send private message  E-mail  Edit post Reply with quote


@RojaN Returned To be honest, I don't really know the answer to your question/problem. The only thing that I know is that -skyfix is/was a hack to get rid of some artefacts on some skyboxes with some graphics cards.
You can have a look at the README from q3map2 here: https://gitlab.com/xonotic/netradiant/b ... 2.txt#L111
This means to me -skyfix has nothing to to with culling. Moreover iirc you should NOT use -skyfix anymore (the drivers have changed, and I think some idtech3 engines fixed this bug as well (ioquake3, Xreal)).
It was a hack in the past, and it is very likely that this hack nowadays produces an error.
Do you have rendering issues with your skybox? If no, than avoid using this switch. I have to admit that his is not really a technical explanation why you have this bug.
Culling can be done either by HINT brushes or Areaportals etc.

@dONKEY Why should he NOT? It's the correct way of sealing doors and cull vis.
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dONKEY
The Afflicted
The Afflicted
Joined: 14 Oct 2001
Posts: 579
PostPosted: 07-09-2019 08:59 PM           Profile Send private message  E-mail  Edit post Reply with quote


I didn’t say you shouldn’t use area portals, I just asked why. It struck me that it wouldn’t necessarily be a first call to controlling vis in Q3A. Doors a a bit more SP. Also areaportaled doors have a nasty bug in spectator mode, certainly in VQ3.
Again, no biggy if someone wants doors in their map, I just thought it was unusual.
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RojaN Returned
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Joined: 25 May 2016
Posts: 41
PostPosted: 07-11-2019 06:03 AM           Profile Send private message  E-mail  Edit post Reply with quote


Thanks, guys. I've seen the black borders in Q3 with my old ATi/AMD card, but I'm on Nvidea now, which never had the bug -skyfix adresses. Ioquake fixes the bug even for AMD. I was told to use it here by Eraser a couple of years back.

Quote:
-skyfix

Enables fix for buggy ATI GL_CLAMP behavior. Always use this.
Sidenote: ATI's behavior is correct. The bug was with *NVIDIA* drivers not distinguishing between GL_CLAMP and GL_CLAMP_TO_EDGE, and Q3 using the wrong one: since Q3 development was done predominantly on nVidia hardware, nobody noticed it until too late.


Anyhow, only ATi/AMD users with the original ID builds should see the cracks. Just strange that it would create this performance issue.

As to why areaportals: one, my maps are big and could use the help, and two, there's a definite SP/narrative aspect. This stuff is moving towards an actual SP game, eventually, and these would then be the MP versions of the maps from the SP game. :D
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