IRC log for #brlcad on 20080712

00:11.49 yukonbob Ralith: re: source -- yes. It's in DocBook format, suitable for html if you like.
00:12.06 yukonbob grab the distro from svn and checkout /doc
00:12.16 yukonbob s/checkout/look in/
00:12.20 yukonbob ~svn
00:12.20 ibot Subversion (aka SVN) is version control software that aims to be a better CVS than CVS. See http://subversion.tigris.org/.
00:12.55 yukonbob ~distribution
00:12.55 ibot distribution is probably a collection of goodies built around a kernel, also a whole lot of infrastructure and people.
00:13.00 yukonbob gah
00:13.19 pacman87 ~cadsvn
00:13.20 ibot To obtain BRL-CAD from Subversion: svn checkout https://brlcad.svn.sourceforge.net/svnroot/brlcad/brlcad/trunk brlcad
00:13.39 yukonbob ya, what he said.
00:13.43 yukonbob :P
00:13.48 yukonbob pacman87: hi :)
00:13.53 pacman87 yukonbob: howdy
00:14.02 yukonbob happy friday
00:14.25 CIA-60 BRL-CAD: 03andrecastelo * r31803 10/brlcad/trunk/misc/win32-msvc9/libged/libged.vcproj: Added files to libged.vcproj.
00:17.49 Ralith yukonbob: cool, tanks. Guess you wouldn't know where to find technical docs on the file format?
00:22.45 yukonbob well, there's the source, for one -- otherwise, I don't think I've personally come across a technical paper describing it, no...
00:22.58 pacman87 g2asc?
00:25.58 Ralith what about it?
00:25.59 Ralith also, brb
00:26.16 Ralith yukonbob: so long as the relevant code's well commented that's not too bad.
00:36.24 brlcad Ralith: no, v5 is the current .g file format revision
00:36.36 brlcad the database format is versioned separately from the rest of brl-cad
00:37.01 brlcad v4 and v5 are all that you'd ever encounter
00:37.26 brlcad it's been v5 since about release 5.0 (just coincidence they match)
00:37.41 brlcad andrecastelo: he's on vacation, gets back tomorrow
00:38.34 brlcad Ralith: and docs for the .g format are on the website, under documentation iirc
00:38.46 brlcad best reference are the headers and sources, though
00:39.00 brlcad there are a few minor items out of sync
01:22.32 Ralith Ah, I thought the versioning thing might be the case.
01:30.18 andrecastelo brlcad: hm ok ok :D
01:30.36 andrecastelo I was kind of worried since the mid term evaluations end monday
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02:00.48 brlcad starseeker: other huge payoff I forgot to mention, decoupling from X11 on Mac -- having a "BRL-CAD Shell" and MGED that work identical and natively on Mac and Windows
02:01.15 brlcad andrecastelo: no worries on your part, the admins back the mentors up if needed
02:01.41 Ralith that reminds me
02:02.06 Ralith why does brl-cad have its own command window thing instead of just opening the shell in the terminal it was launched from?
02:02.30 pacman87 Ralith: that's classic mode
02:02.33 pacman87 mged -c
02:02.52 Ralith oh, cool.
02:03.42 brlcad you can run both simultaneously too
02:03.57 brlcad mged -c, select nu or X, then run "gui"
02:04.50 brlcad another fun way, mged -c, select nu or X, then run "attach X" for as many window views as you want
02:07.31 Ralith fun!
02:09.08 Ralith how hard would it be to get the command equivalent of arbitrary GUI actions automatically?
02:15.28 brlcad depends which gui actions, what actions they're taking
02:15.48 brlcad some of the tcl logic is actually processed in tcl for the tcl/tk interface
02:15.54 brlcad most of it isn't though
02:16.21 Ralith was imagining that it might be educational to have that sort of thing dumped to stdout or somewhere every time an action was performed
02:16.26 brlcad for editing, you can get most of the options on the faceplate with the 'press' command
02:16.40 brlcad the geometry browser does exactly that
02:17.03 brlcad it'll output every command that corresponds to what it's showing
02:17.24 brlcad the main menu actions, though, are a hybrid mix
02:17.30 Ralith neat
02:17.35 Ralith kk
02:17.57 brlcad "press help" to get a list of built-in actions press supports
02:18.56 brlcad if you "sed some_primitive" .. it goes into edit mode, with the faceplate gui enabled, you get a menu in the graphics context. you can run: press "Menu Option" to press most of the edit operations and run the "p" command or mouse edit from there
02:19.46 Ralith sounds useful
02:19.50 Ralith especially if I ever have to script something
02:25.22 brlcad yep
02:25.51 brlcad the mged quick reference card is a good starting point for learning what commands are available, and their categorization
02:25.56 brlcad (tis on the website)
02:26.38 brlcad ~botmail for mafm: http://www.ogre3d.org/docs/api/html/classOgre_1_1ManualObject.html .. looks like what we'd need for rendering wireframes/points manually
02:27.50 Ralith Hm. In following the tutorials in the introduction to mged, it's apparent that the raytracer makes visible objects which are arguably hidden, such as the intersection between a two objects rendered along with the difference between two objects taken in both directions.
02:27.54 Ralith Is this intentional?
02:31.11 brlcad hm?
02:32.37 brlcad what section/page?
02:32.51 Ralith when you create a rcc, then a sph with a centerpoint on the center of the top of the rcc and a radius equal to that of the rcc, then render sph + rcc (an inverted dome) and sph - rcc (an upright dome) and rcc - sph (a cylinder with an inverted dome cutout) you can see a sliver of the sph + rcc.
02:32.58 Ralith sec
02:33.17 brlcad or screenshot
02:33.17 Ralith pdf page 57 == real page 45
02:33.28 Ralith said sliver is visible both in the image in the pdf and in the actual rendering
02:38.30 brlcad ah! I see what you're getting at
02:39.27 brlcad they're not hidden, for that particular intersection it just numerically happens to work out that there is overlap on the tangency (which naturally extends all the way to the surface)
02:40.12 Ralith tangency?
02:40.46 brlcad where the cynlinder meets the sphere, it's perfectly tangent to the sphere's surface
02:41.21 brlcad so there is a thin sliver of material there where they both exist on the exterior
02:41.34 Ralith isn't that infinitely thin, though?
02:41.40 Ralith and therefore invisible?
02:41.51 Ralith or does the raytracer make approximations necessary for performance reasons?
02:42.37 brlcad sure, that sliver's thickness numerically approaches being infinitely thin with inifinite precision arithmetic
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02:43.15 brlcad but yes, performing infininte precision or even fixed precision is two-to-three orders of magnitude slower than floating point
02:43.16 Ralith ahh.
02:43.36 Ralith so it's proportional to the actual way the math is being performed.
02:43.37 Ralith neat!
02:43.50 Ralith thanks for the in-depth answer
02:44.23 brlcad and for the sake of being a *solid* modeling engine and a solid model ray-tracer, you want all sements and objects have some real non-infinite thickness when sampled for analytic purposes
02:44.34 Ralith I had no idea that that was the sort of place floating point imprecision became visible, but I guess if it's reasonable anywhere it's places like that.
02:45.16 Ralith yeah, I thought it might actually be intentional for those reasons, but sacrificing accuracy because of that alone seemed strange.
02:45.39 brlcad oh yeah, floating point precision can wreak absolute hell if it's not managed consistently and robust -- our librt library goes through extensive hoops to validate and do its best to stabilize the numerics
02:57.29 Ralith the primitive selection menu appears to be broken in the latest release.
02:57.44 Ralith when I click an item, the console gives this error:
02:57.45 Ralith db_lookup(-n) failed: -n does not exist
02:57.45 Ralith bgerror failed to handle background error.
02:57.45 Ralith Original error:
02:57.45 Ralith Error in bgerror: window name "_secErrorDialog" already exists in parent
03:25.29 Ralith brlcad: any ideas?
04:20.53 Ralith I can't work out how to do this on the command line, so it's blocking my use of brl-cad just as I was learning enough to do cool things :/
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18:47.46 Ralith anybody about?
18:49.24 Ralith I'm getting progress-halting errors when progressing through the goblet tutorial
18:52.06 Ralith Specifically, when I try to use the GUI primitive selection tool, I get the following errors (one is printed each time I click on a primitive in the list): http://codepad.org/YHA1WcK4
19:08.21 Ralith ah, *there's* the command line version. The gui bug is still annoying, though.
19:15.46 Ralith also, occasionally the command window opens at a very small size.
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20:32.57 ``Erik O.o
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20:57.18 brlcad Ralith: howdy
20:58.53 brlcad yeah, that's a known bug that happened in the latest release, you can either revert to a previous binary or ..
20:59.03 brlcad follow the suggestion I mention here: http://sourceforge.net/forum/message.php?msg_id=5088783
21:16.04 Ralith cool, thank
21:16.04 Ralith s
21:44.42 brlcad dives into obscene quantities of sushi he picked up on the way home
21:52.21 ``Erik heh
21:52.26 ``Erik that tofi place?
22:27.04 Ralith mm, sushi
22:45.49 brlcad yeah, pretty decent
22:46.06 brlcad huge thick pieces of sashimi
22:46.48 Ralith I need to get more good sushi
22:46.56 Ralith standard store stuff sucks
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