IRC log for #brlcad on 20071025

06:29.32 *** join/#brlcad tom_ (n=chatzill@mmds-216-19-44-150.sqpk.az.commspeed.net)
06:34.48 *** join/#brlcad tom___ (n=tom@mmds-216-19-44-150.sqpk.az.commspeed.net)
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16:51.53 *** join/#brlcad waterpie (n=waterpie@athedsl-336989.home.otenet.gr)
16:52.15 waterpie hi all
16:55.28 waterpie q: i have no knowledge of brlcad. i just want to convert an iges file to eg dxf. i try "iges-g -3 -o f3.g f.iges" and then "g-dxf -o f3.dxf f3.g" but does nothing. it seems that it misses a "sample-object" at the end, but i have no idea what it is/how to make it. any help pls?
17:06.56 brlcad when you do g-dxf, you have to tell it what object(s) to convert
17:07.10 brlcad when you did iges-g, it created at least one object for you
17:07.18 brlcad run mged -c f3.g tops
17:07.31 brlcad that should list the top-level objects, you can then use that name for g-dxf
17:14.15 waterpie brlcad: mged -c f3.g tops --> _GLOBAL running: g-dxf -o f3.dxf f3.g _GLOBAL --> _GLOBAL is not a drawable database object 0 triangles written
17:14.42 brlcad yeah _GLOBAL is not a geometry object
17:14.48 brlcad is there no other object listed?
17:15.07 waterpie no
17:15.28 brlcad then there wasn't any geometry detected/converted during iges-g
17:15.45 brlcad it should have said in the output that there were 0 objects converted
17:15.59 brlcad can you pastebin the output from iges-g?
17:16.02 brlcad ~pastebin
17:16.03 ibot [pastebin] a place to paste your stuff without flooding the channel - try http://pastebin.ca, or http://channels.debian.net/paste, or http://rafb.net/paste/, or http://pastebin.com is usually painfully too slow and unresponsive to use, use one of the other pastebin sites, or dpaste.com is a very nice pastebin as well
17:16.12 brlcad er
17:16.15 brlcad ~bzpaste
17:16.20 brlcad ~bzpastebin
17:16.20 ibot somebody said bzpastebin was http://pastebin.bzflag.bz a place to put large chunks of text to not flood a channel
17:16.29 brlcad yeah, there
17:19.07 waterpie http://pastebin.bzflag.bz/d4b57b251
17:21.10 brlcad ah, several 'issues'
17:21.59 brlcad "Unrecognized IGES version" for starters, meaning that solidworks is probably exporting one of the newer iges formats, but it still finds 1001 entities, so should be fine for conversion
17:22.07 brlcad but at the bottom it says the problem
17:22.31 brlcad it contains spline surfaces, so you need the -n option
17:23.06 brlcad either -n or -t
17:23.18 brlcad try both, should get different results
17:24.01 waterpie it is either or. each one looses the info of the other?
17:24.23 brlcad yeah, not both
17:24.43 brlcad it's not so much that it looses information moreso than it tries a different conversion approach
17:25.28 *** join/#brlcad Z80-Boy (n=clock@zux221-122-143.adsl.green.ch)
17:25.32 brlcad just about every format conversion looses information of some type, it's really rare that *something* doesn' change
17:26.01 waterpie -t core dumps
17:26.20 brlcad hm, that's not a good sign
17:26.57 brlcad can you paste the fin_assembly.igs somewhere where I can test it?
17:27.04 brlcad s/paste/post/
17:32.34 waterpie i give up. i will try to get the file in different format in the first place.
17:32.40 waterpie thanks for your help
18:15.08 *** join/#brlcad yukonbob (n=yukonbob@CPE001125477e9c-CM0011e6be27b1.cpe.net.cable.rogers.com)
18:18.55 yukonbob hello, cadheads
18:58.32 louipc damned vampires
19:14.45 yukonbob halloween coming early for you louipc?
19:16.39 louipc they don't only come out on halloween
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21:11.48 *** join/#brlcad IriX64 (n=mariodot@bas2-sudbury98-1177871835.dsl.bell.ca)
21:34.18 *** join/#brlcad yukonbob (n=yukonbob@CPE001125477e9c-CM0011e6be27b1.cpe.net.cable.rogers.com)
22:05.21 starseeker brlcad: Is the facetizer part of the converter?
22:05.30 brlcad it's part of a lot of the converter
22:05.41 brlcad it's what turns a given model into a set of polygons
22:06.15 brlcad not so much heavy math as an utter slew of logic
22:06.27 starseeker ah
22:06.30 brlcad euler operations on meshes, dealing with floating point arithmetic
22:06.49 brlcad tons of O(n^2) and O(n^3) algorithms
22:06.58 brlcad some that are worse..
22:07.10 brlcad it's the nature of the problem, it's np-complete to start with
22:07.29 starseeker Oh, OK - so it's not the "well, this one is easier to implement" effect?
22:07.33 brlcad aside from the practicle aspects of dealing with floating point and modeling issues
22:07.43 brlcad oh no, not at all
22:08.12 brlcad it's actually not a bad approach, just exceptionally hard to implement well as you're already starting from a degraded state
22:08.33 starseeker Are the major formats at least well documented, or is it kind of a CAD version of the MS Word effect?
22:09.02 brlcad it's not really a format, it's the core "how do you deal with solid geometry in a mesh format"
22:09.11 starseeker Oh, OK.
22:09.25 brlcad at least, the "format" is just a "boundary representation"
22:09.40 brlcad there are some choices there, whether it be something like brl-cad's n-manifold geometry
22:09.48 brlcad or winged edge data structures, or others
22:10.16 brlcad but the base problem is "give me a mesh of this object that is guaranteed to be solid geometry" .. and that turns out to being a pretty hard problem
22:10.33 starseeker Oh, OK.
22:10.37 brlcad especially with floating point math and "unclean" geometry that you always encounter
22:11.43 starseeker Can you help by doing related/derivative dimensions? (I.e. "this length is always exactly 2x the length of this" - not sure what the technical term would be)
22:13.35 brlcad there is some book-keeping you can do, but you very quickly/often end up with a situation where code-wise you don't really know the intent, so either case for A or B can be wrong
22:14.03 brlcad that would be a dimensioning constraint
22:14.33 brlcad you still are trying to make a mesh, and all you have to go with is a mess of polygon soup
22:14.49 brlcad a closed mesh
22:15.14 starseeker Hmm
22:15.24 starseeker nasty
22:15.30 brlcad most of content packages (e.g. blender) can get away with a lot of the mesh operations because they rarely ever have to ensure closure, just how it looks
22:16.04 starseeker So as long as the imperfection there is "non-visual" on some scale, it doesn't matter?
22:16.30 brlcad anyways, that's one of the reasons for wanting b-rep support at our primitive level, and b-rep csg operations
22:16.41 starseeker right
22:17.22 brlcad that would let us retain the topological structure all the way up to the point that the mesh itself is created, and can then be directly done given the already evaluated surfaces instead of evaluating csg on mesh after mesh
22:18.34 starseeker Elegant.
22:19.22 starseeker How disruptive is primitive b-rep support?
22:19.36 brlcad disruptive?
22:19.44 brlcad not at all
22:19.50 brlcad just an entirely different paradigm :)
22:20.02 starseeker So it can be added without disturbing too much of the existing code?
22:20.03 brlcad some of the work is already complete, massive undertaking
22:20.06 brlcad oh yeah
22:20.08 brlcad easily
22:20.13 brlcad some of it's already there
22:20.15 starseeker Cool - that helps
22:20.31 brlcad for maybe three or four of the primtiives, plus the entire brep/nurbs representation support is pretty much done
22:20.49 starseeker cool!
22:21.03 brlcad so have to add the rest of the primitives, then work on csg evaluation of brep on brep and work on fast brep tessellation
22:21.28 brlcad those three pieces done, then we have clean facetization of any csg model as well as things like opengl shaded displays
22:22.13 starseeker Nice!
22:24.41 starseeker Naive question - the existence of brep at a primitive level - how does that make the core logic of model -> mesh simpler? Would it mean that models would have to be rebuilt with the new primitive or would the conversion of old primitives to brep be less expensive?
22:25.55 starseeker IriX64: Dare we ask?
22:26.07 IriX64 vista64 :)
22:26.54 IriX64 heh i haven't tossed my cookies .... yet :)
22:27.22 starseeker Sooo... does BRL-CAD work on it? ;-)
22:27.40 IriX64 yes actually more to come on that :)
22:28.43 IriX64 brlcad=busy man
22:29.14 starseeker Heh - one dumb question too many I guess
22:29.36 IriX64 no such thing as dumb question if i don't know the answer someone else does said somebody to me
22:31.31 starseeker The thought skittered through my brain that the fundamental problem of converting shapes to meshes has to be solved somewhere - maybe std. primitive -> brep -> mesh is cleaner theoretically than std. primitive -> mesh?
22:43.25 yukonbob starseeker: yesterday (?) I posted some diffs that might help you w/ running tcl/tk 8.4; (it was you that was interested in this, right? With ebuilds?)
22:43.33 louipc hmm I don't know why I'd want to change a csg model to brep
22:44.21 IriX64 http://www.irix32.spaces.live.com/photos/brlcaddoesvista64 and also /vista64 :)
22:45.02 starseeker yukonbob: Not me per-say - Gentoo devs would probably like it, but I'm OK with using the internal one
22:45.26 IriX64 well the brlcad albumn :)
22:45.43 louipc starseeker: no ebuilds for tcl8.5a?
22:46.29 starseeker louipc: They are but they are "masked" meaning they are unstable
22:46.53 starseeker BRL-CAD isn't unstable, so I would prefer not to rely on an unstable ebuild when it is merged (IF it is merged... grumble...)
22:47.23 starseeker yukonbob: I think I saw some of that - how extensive are the diffs?
22:47.33 louipc I think they're only classified as unstable because it's alpha
22:47.54 starseeker louipc: Right, but that doesn't change it unfortunately - we would need a stable 8.5
22:48.09 louipc unless you use tcl for other things I bet it's ok to install them seperately
22:48.35 starseeker yukonbob: I already need to patch once for tcl, so patching to work with 8.4 actually isn't impossible
22:48.36 louipc brl-cad is distributing the tcl8.5a though
22:49.10 starseeker louipc: Right. That's my preference, but it seems to give some of the devs hives...
22:49.21 louipc same as you get anywhere else
22:49.32 louipc eg. in the 8.5a ebuild
22:50.05 louipc you should try it though ;)
22:50.07 starseeker Once we install into /opt all the nasty problems go away. To me that seems to be the obvious way to go - if we end up having to have a binary install it would go there anyway...
22:50.22 louipc yeap opt helps
22:50.36 starseeker yukonbob: Still here?
22:50.46 louipc but there's no use having tcl installed twice hah
22:50.53 starseeker That's their thinking
22:51.04 louipc but there isn't...
22:51.41 starseeker I suppose, but it's simpler to just have brlcad install exactly what it needs and we don't have to argue about the mask on tcl 8.5...
22:51.44 louipc did it not work with 8.5a installed separately?
22:51.49 starseeker probably it does
22:51.58 starseeker I can try it
22:52.30 louipc yeah I would
22:52.58 starseeker hard drives are so cheap today the simpler solution appeals though
22:53.40 louipc not to me, and probably a lot of other folks :P
22:54.05 starseeker So I've noticed.
22:54.22 starseeker All I need to do is install it, and the rest should follow.
22:54.59 starseeker The ebuild actually doesn't specify one way or the other, so if you install tcl 8.5 it SHOULD work.
22:55.49 louipc yeah true the config will pick it up
22:56.41 starseeker Putting tcl and tk in the package.keywords file didn't bump the upgrades - they must be hard masked
22:57.16 starseeker Yep - hard masked in /usr/portage/profiles/package.mask
22:59.58 yukonbob louipc: re: unstable -- there still seems to be legitimate issues around 8.5 that would be "unstable"... which is why it's still beta (not alpha anymore)... but that said, it's got some new work under the hood that won't be proven stable until it's more widely deployed/tested... so in that case, basing a product (ie: brl-cad) on it is a bit risky...
23:00.49 starseeker Generally I don't mess with something that is hard masked - it's a bit of a pain and oftentimes risky
23:01.33 louipc yeah brl-cad already uses it though hehe
23:02.02 starseeker yukonbob: Are the patches still online somewhere? Maybe including those patches will push brl-cad into the acceptable category
23:04.19 yukonbob starseeker: I posted them in pastebin.bzflag.bz -- my build env is pkgsrc on netbsd, so w/i that framework (and setting up working dependencies, configs for the env), the mods I made swap-out 8.6 for tcl/tk for 8.4 (there is no tcl/tk 8.6), and I also completely remove itcl, itk, urt, and a few others where I can properly modularize the build and use itcl packages, urt packages, etc., etc.
23:06.10 louipc yeah I have to make itcl, itk, etc packages
23:06.37 louipc tcl extensions are kinda odd
23:06.55 yukonbob louipc: that's the smart way to go -- that way you can manage it w/ your package tools...
23:07.14 louipc (the way you're supposed to keep sources, build-stubs)
23:07.15 yukonbob rather than having it as a non-defined "lump" that's part of a bigger install (brlcad).
23:07.37 louipc yukonbob: yea it's ideal
23:07.52 louipc even brlcad can be broken up into a few
23:07.55 yukonbob http://pastebin.bzflag.bz/m2121d14e
23:08.35 yukonbob <PROTECTED>
23:08.47 louipc mged, librt, rt, conv, ...
23:09.08 yukonbob http://pastebin.bzflag.bz/meb2598chttp://pastebin.bzflag.bz/meb2598c
23:09.13 yukonbob http://pastebin.bzflag.bz/meb2598c
23:10.05 starseeker yukonbob: Thanks!
23:10.13 yukonbob (last one gets rid of bwish, which I don't use, and I'm experimenting w/ setting up a loadable lib for plain-jane tclsh/wish, rather than "another" wish client...
23:10.16 yukonbob )
23:10.28 yukonbob starseeker: np -- hope you find something useful.
23:15.59 yukonbob I use pkgs for libpng, urt (Utah Raster Toolkit), tcl, tk, incr tcl (itcl/itk), blt, and tkimg. configure is instructed to not build included copies, and I also disable jove, because I just use whatever my favourite already-installed editor is...

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