IRC log for #brlcad on 20090716

00:17.40 starseeker brlcad: cool, I hadn't heard of the FLOSS weekly
00:17.52 Ralith plugging is good.
00:19.26 starseeker is curious if Ralith can write down his insights on what it would take to do shared context Qt/Ogre
00:19.35 starseeker still wants to do that, somehow or other
00:19.39 Ralith starseeker: did you already read the wiki entry?
00:20.30 Ralith it wouldn't be hard, really
00:21.05 Ralith just take things back to when the OgreScene approach was fully implemented, and add hello->show(); after the rest of the widget test code, and remove the resize call
00:21.10 Ralith from main
00:21.21 Ralith and if that doesn't work, try the same thing on the QtRenderListener approach
00:21.35 Ralith and if that doesn't work, then I guess we're doing things this as best we can right now.
00:21.41 starseeker nods
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01:07.48 ``Erik *pant* 80 pounds of empty boxes, paper bags, junkmail and newpapers prepped for recycling day
01:09.03 Ralith starseeker: you gunna take a whack at it?
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02:22.08 ``Erik ~seen madant
02:22.09 ibot madant <i=cb7baf0f@gateway/web/freenode/x-a32eed164597bd06> was last seen on IRC in channel #brlcad, 12d 6h 15s ago, saying: 'nothing more disastrous than non-cooperative softwares ;)'.
02:22.26 ``Erik ~seen homovulgaris
02:22.27 ibot homovulgaris <n=d@117.196.131.215> was last seen on IRC in channel #brlcad, 338d 22h 29m 56s ago, saying: 'sean, on a scale of 1 to 10 how much trouble would one face when trying to make a .deb package for brlcad ?'.
02:22.37 ``Erik hm.
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02:32.06 ``Erik oscilloscope spam, wow
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04:00.35 starseeker Ralith: probably at some point
04:10.34 Ralith cool :)
04:10.55 Ralith I'll try to code everything else such that it'll be easy to transition if you get it working
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08:38.29 CIA-30 BRL-CAD: 03d_rossberg * r35148 10/brlcad/trunk/src/libbn/multipoly.c:
08:38.30 CIA-30 BRL-CAD: replaced c99 idiom with c89 compatible one
08:38.32 CIA-30 BRL-CAD: (all declarations have to be on top of a block)
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10:14.32 d-lo ~seen d-lo
10:14.33 ibot d-lo <n=claymore@bz.bzflag.bz> was last seen on IRC in channel #brlcad, 1s ago, saying: '~seen d-lo'.
10:14.40 d-lo muwahaha
10:14.48 d-lo mernin all!
10:16.53 ``Erik yaegh
10:17.08 ``Erik yargh, even
10:17.11 d-lo whoa. up early or up late?
10:17.42 ``Erik earlyish
10:18.08 ``Erik been getting up at five something the last few weeks
10:18.51 d-lo nice.
11:56.16 CIA-30 BRL-CAD: 03erikgreenwald * r35149 10/brlcad/trunk/src/rt/viewweight.c: slightly more verbose logging if no density file is handy.
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12:47.48 starseeker winces as he now begins to understand some of the design considerations that may have driven the original design of opennurbs_ext
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12:49.02 brlcad ``Erik: you have a pine session going nuts
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13:05.09 ``Erik that machine gets gimpy with locks :/ I can't even start mutt due to mail locks going wonky
13:07.30 ``Erik lame, sometimes we get .so.0 and sometimes .so.0.0
13:08.35 brlcad needs a -version-info 19:1 LDFLAGS in the makeifle.amd
13:10.43 ``Erik hrm *shrug* fbsd6 gives .so.0 and fbsd7+ gives .so.0.0 on our core libs, supposedly
13:11.12 ``Erik ah, wait, no, not our core
13:11.15 brlcad hm, doesn't sound right
13:11.17 ``Erik just the step stuff
13:11.21 brlcad yeah, the new libs
13:11.26 ``Erik http://people.freebsd.org/~amdmi3/brlcad-7.14.8.log
13:11.26 brlcad none of them have -version-info
13:12.53 brlcad with it, they should list better and the packing list can be fixed
13:13.39 ``Erik yeah, editing now
13:13.54 ``Erik but I blew away my macports stuff, so I gotta get that up enough to test
13:15.43 brlcad probably shouldn't be 19:1
13:16.18 brlcad don't know what it "should" be without re-reading the libtool docs on verison-info and checking up on step's version
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15:16.20 ``Erik O.o http://www.alexa.com/siteinfo/brlcad.org
15:18.47 louipc canada wins
15:18.58 louipc ok not really
15:20.42 starseeker brlcad: when will they post your interview?
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16:22.00 CIA-30 BRL-CAD: 03starseeker * r35150 10/brlcad/trunk/include/opennurbs_ext.h: BASegment isn't serving any purpose - remove it.
16:33.38 CIA-30 BRL-CAD: 03starseeker * r35151 10/brlcad/trunk/include/opennurbs_ext.h: Don't use intersectedBy for a SubcurveBANode
16:44.51 CIA-30 BRL-CAD: 03starseeker * r35152 10/brlcad/trunk/include/opennurbs_ext.h: Add a few comments, formatting.
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17:46.18 jdoliner indianlarry you around?
17:49.06 CIA-30 BRL-CAD: 03starseeker * r35153 10/brlcad/trunk/ (4 files in 3 dirs): Merge BANode and SubcurveBANode classes into one BANode class
18:00.03 ``Erik jabs indianlarry with a pointy stick
18:00.24 indianlarry hey joe what's up
18:04.10 CIA-30 BRL-CAD: 03starseeker * r35154 10/brlcad/trunk/include/opennurbs_ext.h: Move CurveTree class before BVNode definitions
18:06.26 jdoliner hi
18:07.20 indianlarry hey joe
18:07.34 jdoliner and it seems that even the numerical solutions use some algebraic stuff
18:08.57 jdoliner it seems they're needed for finding basepoints
18:09.17 indianlarry basepoints?
18:09.30 jdoliner yeah what I mean by that
18:09.45 jdoliner is that if we want to march along the intersection
18:10.08 jdoliner we need a place to start that's on the intersection
18:10.11 jdoliner curve
18:13.14 jdoliner So I've been looking through a couple of CAS implementations to see how they handle these sorts of things
18:14.03 indianlarry what's in the algebra, do they subdivide into near flat pieces like the raytracing and then intersect planes for a starting point?
18:14.53 indianlarry could use bounding box to see what parts of the surface a near
18:15.01 indianlarry are near
18:15.56 jdoliner no they use the high level stuff like Groebner bases to solve things
18:16.48 ``Erik *yawn*
18:17.12 CIA-30 BRL-CAD: 03erikgreenwald * r35155 10/brlcad/trunk/src/other/step/src/ (6 files in 6 dirs): chuck in some version info for installed libraries. Mimick BRL-CAD lib version (for now).
18:18.17 jdoliner describe to me more how subdividing would work
18:20.31 indianlarry for raytracing we currently subdivide each surface (in UV) until it is near flat
18:22.21 indianlarry a 3D bounding box is computed for each near flat surface and put into a surface tree
18:22.33 jdoliner okay
18:22.52 indianlarry rays are first cast against the bounding boxes
18:23.53 indianlarry for bounding boxes hit an iterative approach is used
18:24.22 indianlarry two intersecting/perp planes are used to represent the ray
18:25.09 indianlarry and an initial starting point in that sub-surfaces UV (possibly multiple start points)
18:28.49 indianlarry given two bboxes from seperate surfaces overlap
18:29.40 indianlarry use normals of each subsurface to setup walking direction
18:30.14 indianlarry adjust normals as you walk
18:33.09 jdoliner okay that makes sense
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18:33.21 indianlarry walk on each surface, plane of two normals along with the plane of from surface normals and a perp plane along their average
18:33.38 indianlarry just thinkin out load
18:33.41 indianlarry loud
18:34.56 jdoliner so yeah if we have two surface's and a point on their intersection curve, then going iteratively from the point along the cross of the normals will keep us on the curve?
18:35.12 jdoliner provided we take small steps
18:35.32 jdoliner and our geometry is "nice"
18:36.28 indianlarry that can be a problem
18:37.02 indianlarry especially with boundary trims where the UV extent is the intersection
18:37.42 indianlarry you will also need to check in/out of trim
18:38.02 indianlarry unless you just start with untrimmed surfaces
18:38.06 indianlarry your call
18:38.25 indianlarry i'd start with the untrimmed surfaces ;^)
18:39.39 indianlarry though wwe do have trim in/out closeness checking
18:40.06 jdoliner do you mean by "the UV extent is the intersection"
18:41.20 jdoliner what do you mean by the above?
18:41.21 jdoliner whoops
18:43.14 jdoliner also have we considered adding in some algebraic geometry functionality in brlcad?
18:45.21 CIA-30 BRL-CAD: 03erikgreenwald * r35156 10/brlcad/trunk/src/librt/primitives/nmg/nmg_manif.c: fix some sign issues with the paint table? maybe?
18:46.27 indianlarry the intersection between to surfaces can lie along one of the surfaces UV boundary
18:47.19 indianlarry two
18:48.03 indianlarry have to make sure the iterator doesn't step out of UV that's all
18:48.29 jdoliner yeah that would be a problem
18:49.37 indianlarry if your up to it try out the algebraic solution and if it looks a bit much we'll go back to iterative approach
18:51.26 jdoliner k I like that idea
18:52.06 jdoliner groebner bases and stuff can be really powerful
18:52.46 indianlarry cool, look forward to seeing what you come up with
18:53.25 jdoliner does this go in libbn you think?
18:54.14 ``Erik dang that indianlarry is a slavedriver O.o
18:55.22 indianlarry up to you, if you'd like to keep it in procdb while your testing i'm okay with it
18:56.07 jdoliner also a question on etiquette because I haven't really done this before
18:56.30 jdoliner I'm planning to draw heavily from an opensource library called CoCoa in my implementation
18:56.39 indianlarry indianlarry looks for dictionary
18:57.06 ``Erik jdoliner is out to confuse us mac weenies
18:57.23 jdoliner I don't think we want to just include their library as external code, because a lot of it isn't going to be that useful
18:58.12 jdoliner it's GPLed and all so I think this is okay
18:58.30 ``Erik um, we're not gpl
18:58.46 ``Erik we're bsd and a little lgpl, some of our consumers cannot abide by gpl
18:58.58 jdoliner I see
18:59.05 ``Erik (like, consumers that let us have paychecks) :)
18:59.24 jdoliner ah that kind of consumer I see
19:00.49 jdoliner so if we just "stole" the code and put it in our project, we would need that code to be gpled or our entire project. either way it doesn't seem like we can do that
19:02.47 indianlarry it's not unheard of to get special author permission but that would have to be formalized
19:03.13 indianlarry probably more trouble than worth
19:04.07 jdoliner I see
19:04.46 indianlarry erik pointed out that is especially hard with multiple authors as is typical in an open source gpl environment
19:04.46 jdoliner k 2 questions then
19:05.01 jdoliner yeah that would become difficult
19:05.17 jdoliner that license would something have to be under for us not to have to worry at all
19:05.36 ``Erik bsd, mit, apache, ... even lgpl
19:05.58 jdoliner okay then that becomes and option, also how much borrowing will we get in trouble for?
19:07.18 ``Erik if it's a license that permits it, as much as ya want as long as you abide
19:07.55 ``Erik for a bsd style license, that just means you give credit where it's due
19:07.56 indianlarry we don't want to borrow anything we shouldn't
19:08.43 ``Erik but we have code that links to and are linked to by proprietary shtuff, so we cannot snarf gpl stuff :(
19:09.34 ``Erik (we probably have a couple small executables that may be gpl, but the libraries and headers have to be clean)
19:10.28 ``Erik (billy holiday to tool, my playlist is awesome)
19:11.05 jdoliner okay sounds good
19:11.18 ``Erik there's a little discussion in the HACKING file about license crap
19:12.31 jdoliner I guess I just have a good reference to look at for stuff
19:12.53 jdoliner oh well their code isn't actually such a good fit anyways :)
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19:15.10 ``Erik hm, gotta kinda be careful of doing that, the whole 'clean room' issue
19:15.41 ``Erik (I wanna be a coder, not a lawyer, waahhhhh)
19:17.50 CIA-30 BRL-CAD: 03starseeker * r35157 10/brlcad/trunk/ (5 files in 3 dirs): Merge BVNode and SubsurfaceBVNode classes into one BVNode class
19:21.14 jdoliner well along those lines, this algorithm actually doesn't look all that though. I think I can probably just do it from scratch.
19:21.54 jdoliner Perhaps this is Stallman's desired effect from the LGPL
19:21.57 jdoliner and GPL
19:24.12 ``Erik stallman is pushing a religion *shrug*
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19:56.29 brlcad cheers as he gets the big endian to chatter over serial
19:56.58 brlcad starseeker: in a couple days I believe
19:57.43 brlcad ``Erik: heh, I saw that stats site .. most interesting is that it thinks we could make about 8 bucks a day on ads, heh
19:59.05 brlcad jdoliner: if you look at CAS, you're going to find computational geometry approaches, they kinda go hand in hand but aren't the only way to approach the problem (and often suffer massively in terms of performance)
20:04.19 brlcad jdoliner: and yeah, GPL code is certainly out -- we're clean-scrubbed to LGPL or better so at best you can get someone to "explain to you" a technique used in some GPL code, but the code itself cannot be used
20:05.31 brlcad but more to the point of the approach, I'd personally prefer keeping your work isolated in proc-db (could be a subdir for that matter) before injecting a bunch of computational geometry/algebra routines into libbn/librt until we know it works well, at least proof of concept
20:06.29 jdoliner k I've gotten myself a nice Algebra folder setup in proc-db
20:06.36 brlcad otherwise, to add directly to libbn/librt before it's known to be viable, that'd be worthy of a branch
20:06.54 jdoliner do you think Groebner bases are prohibitively inefficient
20:06.55 jdoliner ?
20:07.06 brlcad I think they probably will be :)
20:07.18 jdoliner rats
20:07.46 brlcad most of the algebra-based approaches require stable numerics, with many/most falling back to fixed- or infinite-precision numerics in order for them to work
20:08.09 brlcad which are anywhere from two to four orders of magnitude slower than other approaches
20:08.16 jdoliner the numeric algorithms I've found still use algebra at the starting point though
20:08.28 brlcad it's mostly how do you solve
20:10.26 brlcad I mean you're more than welcome to give it a shot, but you should be rather cautious that it might mean you end up with squat in terms of useful code
20:10.54 brlcad we need surface surface intersections to be fast slightly more than we need them to be exact :)
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20:11.43 jdoliner K
20:12.01 jdoliner well as you can see from my talk with IL
20:12.19 jdoliner the simple approach of just marching the normal's cross seems pretty viable
20:12.31 jdoliner it fails in some boundary cases
20:12.59 brlcad the primary use is going to be for calculating booleans so we can go CSG+primitives -> CSG+NURBS -> untrimmed evaluated NURBS -> polygonal mesh -> triangle mesh
20:13.34 jdoliner oh
20:13.46 jdoliner okay so if a bit of inaccuracy creeps in it might be okay
20:14.01 brlcad as long as it's controlled inaccuracy, sure
20:14.13 brlcad it can't end up with non-solid geometry
20:14.40 jdoliner yeah that's the apocalypse
20:15.22 jdoliner okay well using the normal marching is pretty well setup already seeing as ON already has normal eval builtin.
20:15.26 brlcad that's an axiomatic requirement, and it has to keep the same topological structure/manifolds (if was a 3-manifold when we started, it should be a 3-manifold regardless of the transformation)
20:28.35 CIA-30 BRL-CAD: 03starseeker * r35158 10/brlcad/trunk/ (3 files in 3 dirs): Start preparing to move responsibility for Curve Tree generation and use to the Surface Tree builder, rather than calling it from brep.cpp.
20:57.51 ``Erik ho hum
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