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Re: T-Junctions re-visited
March 20, 2013 11:18AM
Quote
Travis Cobbs
The expectation here is that LDraw files start out with fixed point coordinates, and very often, the transformed coordinate will also be very close to fixed point values (due to transformation matrices often being simple translations, or 90-degree increment rotations). So I wanted to prevent floating point innacuracies from separating two points from each other that were expected to be together.

Ah - I think that the expectation is correct for untransformed locations but likely to be incorrect for transformed ones.

For the untransformed point what you've basically said is: users shouldn't use more than 0.001 LDU, so I'll set up a grid of that spacing, with the gridlines at the half-way points between the canonical values, then bucket. And that makes sense.

But once the transform _stack_ is applied, how do you know where the 'grid lines' in the theoretical 1/1000th LDU grid are? Ignoring scaling, I think that just rotations will hose you. The result of the rotations may be totally misaligned with the grid, and thus two points that were near an even mili-LDU (mLDU?? :-) and would round together now span a 'split point (the points half-way between the canonical values where rounding has to go one way or another).

In other words, I think for untransformed parts your code works but for transformed ones some small sub-set of points that should have been locked together will be pulled apart.

cheers
Ben
SubjectAuthorViewsPosted
T-Junctions re-visited Travis Cobbs670March 11, 2013 10:38PM
Re: T-Junctions re-visited Tim Gould319March 11, 2013 11:31PM
Re: T-Junctions re-visited Roland Melkert306March 12, 2013 11:17AM
Re: T-Junctions re-visited Ben Supnik307March 12, 2013 11:17AM
Re: T-Junctions re-visited Roland Melkert285March 12, 2013 11:22AM
Re: T-Junctions re-visited Ben Supnik288March 12, 2013 11:32AM
Re: T-Junctions re-visited Roland Melkert275March 12, 2013 11:41AM
Re: T-Junctions re-visited Ben Supnik290March 12, 2013 11:55AM
Re: T-Junctions re-visited Roland Melkert294March 13, 2013 10:08AM
Re: T-Junctions re-visited Travis Cobbs301March 13, 2013 11:27AM
Re: T-Junctions re-visited Allen Smith320March 12, 2013 02:01PM
Re: T-Junctions re-visited Michael Heidemann287March 13, 2013 09:27AM
Re: T-Junctions re-visited Ben Supnik285March 13, 2013 10:37AM
Re: T-Junctions re-visited Tim Gould282March 13, 2013 02:31PM
Re: T-Junctions re-visited Michael Heidemann276March 13, 2013 03:42PM
Re: T-Junctions re-visited Michael Heidemann288March 17, 2013 04:35AM
Re: T-Junctions re-visited Ben Supnik252March 17, 2013 08:43AM
Re: T-Junctions re-visited Michael Heidemann251March 17, 2013 08:59AM
Re: T-Junctions re-visited Ben Supnik259March 17, 2013 09:02AM
Re: T-Junctions re-visited Magnus Forsberg250March 17, 2013 09:15AM
Re: T-Junctions re-visited Travis Cobbs331March 17, 2013 10:09PM
Re: T-Junctions re-visited Ben Supnik283March 18, 2013 07:30AM
Re: T-Junctions re-visited Travis Cobbs292March 18, 2013 10:57AM
Re: T-Junctions re-visited Ben Supnik300March 18, 2013 11:27AM
Re: T-Junctions re-visited Travis Cobbs284March 18, 2013 12:23PM
Re: T-Junctions re-visited Ben Supnik302March 18, 2013 01:41PM
Re: T-Junctions re-visited Roland Melkert312March 18, 2013 02:51PM
Re: T-Junctions re-visited Travis Cobbs281March 18, 2013 02:59PM
Re: T-Junctions re-visited Roland Melkert331March 18, 2013 03:41PM
Re: T-Junctions re-visited Ben Supnik317March 18, 2013 06:09PM
Re: T-Junctions re-visited Roland Melkert303March 19, 2013 11:38AM
Re: T-Junctions re-visited Ben Supnik326March 19, 2013 11:43AM
Re: T-Junctions re-visited Roland Melkert336March 19, 2013 07:07PM
Re: T-Junctions re-visited Travis Cobbs311March 19, 2013 10:13PM
Re: T-Junctions re-visited Tim Gould294March 20, 2013 03:56AM
Re: T-Junctions re-visited Travis Cobbs286March 20, 2013 10:13AM
Re: T-Junctions re-visited Ben Supnik273March 20, 2013 10:23AM
Re: T-Junctions re-visited Travis Cobbs283March 20, 2013 10:29AM
Re: T-Junctions re-visited Travis Cobbs290March 20, 2013 10:26AM
Re: T-Junctions re-visited Ben Supnik273March 20, 2013 11:18AM
Re: T-Junctions re-visited Ben Supnik284March 20, 2013 06:42AM
Re: T-Junctions re-visited Roland Melkert274March 20, 2013 11:36AM
Re: T-Junctions re-visited Philippe Hurbain280March 20, 2013 06:36AM
Re: T-Junctions re-visited Ben Supnik309March 20, 2013 06:58AM
Re: T-Junctions re-visited Allen Smith304March 20, 2013 09:08AM
Re: T-Junctions re-visited Roland Melkert305March 20, 2013 11:35AM
Re: T-Junctions re-visited Ben Supnik705March 20, 2013 11:50AM
Re: T-Junctions re-visited Michael Heidemann303March 18, 2013 03:54PM
Re: T-Junctions re-visited Roland Melkert276March 13, 2013 10:03AM
Re: T-Junctions re-visited Tim Gould256March 13, 2013 03:56PM
Re: T-Junctions re-visited Sergio Reano264March 13, 2013 03:51PM
Re: T-Junctions re-visited Roland Melkert326March 13, 2013 04:36PM
Re: T-Junctions re-visited Tim Gould294March 13, 2013 05:10PM
Re: T-Junctions re-visited Ben Supnik278March 14, 2013 08:17PM
Re: T-Junctions re-visited Tim Gould341March 14, 2013 08:41PM
Re: T-Junctions re-visited Ben Supnik335March 15, 2013 10:56AM
Re: T-Junctions re-visited Roland Melkert283March 15, 2013 11:36AM
Re: T-Junctions re-visited Ben Supnik253March 13, 2013 06:58PM
Re: T-Junctions re-visited Roland Melkert271March 13, 2013 07:27PM
Re: T-Junctions re-visited Ben Supnik247March 13, 2013 07:37PM
Re: T-Junctions re-visited Roland Melkert267March 13, 2013 07:59PM
Re: T-Junctions re-visited Ben Supnik295March 13, 2013 08:18PM
Re: T-Junctions re-visited Travis Cobbs315March 14, 2013 03:23PM
Re: T-Junctions re-visited Roland Melkert329March 14, 2013 03:34PM
Re: T-Junctions re-visited Tim Gould343March 14, 2013 03:41PM
Re: T-Junctions re-visited Roland Melkert311March 15, 2013 11:33AM
Re: T-Junctions re-visited Tim Gould269March 13, 2013 07:43PM
Re: T-Junctions re-visited Roland Melkert262March 13, 2013 08:08PM
Re: T-Junctions re-visited Tim Gould266March 13, 2013 08:18PM
Re: T-Junctions re-visited Ben Supnik333March 14, 2013 08:15PM
Re: T-Junctions re-visited Roland Melkert327March 15, 2013 11:29AM
Re: T-Junctions re-visited Travis Cobbs293March 15, 2013 12:27PM
Re: T-Junctions re-visited Ben Supnik314March 15, 2013 05:08PM
Re: T-Junctions re-visited Travis Cobbs303March 16, 2013 11:29PM
Re: T-Junctions re-visited Ben Supnik248March 17, 2013 08:58AM
Re: T-Junctions re-visited Roland Melkert254March 17, 2013 12:35PM
Re: T-Junctions re-visited Travis Cobbs281March 18, 2013 12:28PM
Re: T-Junctions re-visited Travis Cobbs319March 18, 2013 12:32PM
Re: T-Junctions re-visited Roland Melkert295March 18, 2013 05:00PM
Re: T-Junctions re-visited Travis Cobbs331March 18, 2013 11:05PM
Re: T-Junctions re-visited Roland Melkert349March 19, 2013 11:38AM
Re: T-Junctions re-visited Sergio Reano335March 26, 2013 02:46PM
Re: T-Junctions re-visited Roland Melkert281March 27, 2013 11:19AM
Re: T-Junctions re-visited Sergio Reano337March 27, 2013 01:48PM



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