#gemrb@irc.freenode.net logs for 24 Dec 2009 (GMT)

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[20:45:12] <Nomad010> hello
[20:48:55] <Lightkey> "None of the official names for South Africa can be abbreviated to ZA, which is an abbreviation of the Dutch Zuid-Afrika." hehe, did not know that
[20:50:20] <Nomad010> lol
[20:50:39] <Nomad010> i didn't pay much attention to why it was ZA
[20:50:47] <Nomad010> and i live there :p
[20:51:12] <Lightkey> I know, that is why I looked it up
[20:51:41] <Nomad010> i don't suppose you know the gemRB source code inside out?
[20:52:11] <fuzzie> what do you need to know? :)
[20:53:36] <Nomad010> first off, i am bored
[20:53:49] <Lightkey> okay...
[20:54:10] <Nomad010> i was reading the gemrb source code
[20:54:17] <Lightkey> <_<
[20:54:21] <Lightkey> >_>
[20:55:01] <Nomad010> and i saw in Core/Polygon.cpp there was a TODO about the sweepline algorithm in the ComputeTrapezoids function
[20:55:35] <Lightkey> just talk to wjp and fuzzie, they know the code inside out, they live in nederlands
[20:55:45] * Lightkey ducks and cover
[20:55:48] <Nomad010> lol
[20:55:59] <wjp> ZA is close enough :-)
[20:56:22] <wjp> ah, yes, that's my code
[20:56:37] <fuzzie> i was about to comment based on blame :)
[20:56:45] <Nomad010> hehe
[20:57:35] <Nomad010> so i am guessing that you take in a polygon and you convert it into a sequence of trapezoids
[20:57:44] <wjp> exactly
[20:57:46] <Nomad010> using line intersection line sweep
[20:57:51] <wjp> yes
[20:59:04] <Nomad010> hmm, so i'm guessing it's ok if i change the linesweep to keep track of the active list
[20:59:35] <wjp> sure. If it's faster and the result is the same :-)
[21:00:01] <Nomad010> cool, i think it's asymptotically faster
[21:00:07] <fuzzie> lots of varied polygon examples to make results obvious, i guess
[21:00:18] <Nomad010> yeah, i was about to ask
[21:00:30] <Nomad010> are polygons simple
[21:01:25] <Nomad010> and then convex or concave
[21:03:24] <wjp> the current code doesn't assume convex
[21:04:12] <wjp> as for simple... hmm...
[21:07:17] <fuzzie> i seem to remember that convex is required by the original engine for at least some things
[21:07:28] <Nomad010> ahh, what i thought you were doing something else
[21:07:33] <Nomad010> http://www.cs.unc.edu/~dm/CODE/GEM/chapter.html
[21:08:16] <Nomad010> something like that in the picture is what you are doing?
[21:08:27] <wjp> yes, but only step 1
[21:08:31] <Nomad010> yeah ok
[21:09:14] <wjp> (sprite rendering is done line by line, so we want to be able to quickly determine the intersection of a scanline and a polygon. Trapezoids work pretty good for that)
[21:09:25] <wjp> s/good/well/...
[21:11:04] <Nomad010> i learnt about this algorithm in my graphics course
[21:11:06] <fuzzie> we still need a better algorithm for approaching trap polygons
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[21:11:17] <fuzzie> if anyone has time to actually think about this sort of thing
[21:11:30] <Nomad010> trap polygons?
[21:11:57] <Nomad010> oh
[21:12:06] <Nomad010> polygons denoting the area traps are active in
[21:12:09] <fuzzie> mmhm
[21:12:45] <fuzzie> when disarming them the pathfinder needs to find a position which is not inside the trap but is sufficiently close to it
[21:13:21] <fuzzie> just picking a position on the outside of the nearest edge is probably sufficient, it's just someting on my 'think about' list
[21:13:25] <Nomad010> i seem to recall that the original baldur's gate had trouble with that
[21:13:55] <fuzzie> yes :)
[21:13:57] <Nomad010> i recall a few times when imoen would fry herself
[21:14:06] <Nomad010> and everyone else :p
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[22:23:30] <Nomad010> hey fuzzie, one last thing
[22:23:47] <Nomad010> do the polygons come in a specific order
[22:23:53] <Nomad010> CCW/CW
[22:25:54] <Nomad010> oh wait, thats wjp :p
[22:27:52] <wjp> I think they do, but I don't remember
[22:28:05] <Nomad010> ok
[22:28:33] <wjp> it might be in the IESDP file format specs somewhere
[22:28:40] <Nomad010> ahh thanks