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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 Cobbs646March 11, 2013 10:38PM
Re: T-Junctions re-visited Tim Gould301March 11, 2013 11:31PM
Re: T-Junctions re-visited Roland Melkert279March 12, 2013 11:17AM
Re: T-Junctions re-visited Ben Supnik286March 12, 2013 11:17AM
Re: T-Junctions re-visited Roland Melkert260March 12, 2013 11:22AM
Re: T-Junctions re-visited Ben Supnik273March 12, 2013 11:32AM
Re: T-Junctions re-visited Roland Melkert261March 12, 2013 11:41AM
Re: T-Junctions re-visited Ben Supnik273March 12, 2013 11:55AM
Re: T-Junctions re-visited Roland Melkert266March 13, 2013 10:08AM
Re: T-Junctions re-visited Travis Cobbs288March 13, 2013 11:27AM
Re: T-Junctions re-visited Allen Smith310March 12, 2013 02:01PM
Re: T-Junctions re-visited Michael Heidemann275March 13, 2013 09:27AM
Re: T-Junctions re-visited Ben Supnik270March 13, 2013 10:37AM
Re: T-Junctions re-visited Tim Gould258March 13, 2013 02:31PM
Re: T-Junctions re-visited Michael Heidemann261March 13, 2013 03:42PM
Re: T-Junctions re-visited Michael Heidemann258March 17, 2013 04:35AM
Re: T-Junctions re-visited Ben Supnik240March 17, 2013 08:43AM
Re: T-Junctions re-visited Michael Heidemann237March 17, 2013 08:59AM
Re: T-Junctions re-visited Ben Supnik247March 17, 2013 09:02AM
Re: T-Junctions re-visited Magnus Forsberg238March 17, 2013 09:15AM
Re: T-Junctions re-visited Travis Cobbs310March 17, 2013 10:09PM
Re: T-Junctions re-visited Ben Supnik266March 18, 2013 07:30AM
Re: T-Junctions re-visited Travis Cobbs277March 18, 2013 10:57AM
Re: T-Junctions re-visited Ben Supnik285March 18, 2013 11:27AM
Re: T-Junctions re-visited Travis Cobbs268March 18, 2013 12:23PM
Re: T-Junctions re-visited Ben Supnik288March 18, 2013 01:41PM
Re: T-Junctions re-visited Roland Melkert296March 18, 2013 02:51PM
Re: T-Junctions re-visited Travis Cobbs268March 18, 2013 02:59PM
Re: T-Junctions re-visited Roland Melkert294March 18, 2013 03:41PM
Re: T-Junctions re-visited Ben Supnik281March 18, 2013 06:09PM
Re: T-Junctions re-visited Roland Melkert287March 19, 2013 11:38AM
Re: T-Junctions re-visited Ben Supnik309March 19, 2013 11:43AM
Re: T-Junctions re-visited Roland Melkert322March 19, 2013 07:07PM
Re: T-Junctions re-visited Travis Cobbs292March 19, 2013 10:13PM
Re: T-Junctions re-visited Tim Gould279March 20, 2013 03:56AM
Re: T-Junctions re-visited Travis Cobbs267March 20, 2013 10:13AM
Re: T-Junctions re-visited Ben Supnik254March 20, 2013 10:23AM
Re: T-Junctions re-visited Travis Cobbs268March 20, 2013 10:29AM
Re: T-Junctions re-visited Travis Cobbs272March 20, 2013 10:26AM
Re: T-Junctions re-visited Ben Supnik249March 20, 2013 11:18AM
Re: T-Junctions re-visited Ben Supnik267March 20, 2013 06:42AM
Re: T-Junctions re-visited Roland Melkert259March 20, 2013 11:36AM
Re: T-Junctions re-visited Philippe Hurbain262March 20, 2013 06:36AM
Re: T-Junctions re-visited Ben Supnik273March 20, 2013 06:58AM
Re: T-Junctions re-visited Allen Smith279March 20, 2013 09:08AM
Re: T-Junctions re-visited Roland Melkert288March 20, 2013 11:35AM
Re: T-Junctions re-visited Ben Supnik672March 20, 2013 11:50AM
Re: T-Junctions re-visited Michael Heidemann285March 18, 2013 03:54PM
Re: T-Junctions re-visited Roland Melkert261March 13, 2013 10:03AM
Re: T-Junctions re-visited Tim Gould243March 13, 2013 03:56PM
Re: T-Junctions re-visited Sergio Reano250March 13, 2013 03:51PM
Re: T-Junctions re-visited Roland Melkert309March 13, 2013 04:36PM
Re: T-Junctions re-visited Tim Gould273March 13, 2013 05:10PM
Re: T-Junctions re-visited Ben Supnik255March 14, 2013 08:17PM
Re: T-Junctions re-visited Tim Gould327March 14, 2013 08:41PM
Re: T-Junctions re-visited Ben Supnik319March 15, 2013 10:56AM
Re: T-Junctions re-visited Roland Melkert270March 15, 2013 11:36AM
Re: T-Junctions re-visited Ben Supnik240March 13, 2013 06:58PM
Re: T-Junctions re-visited Roland Melkert257March 13, 2013 07:27PM
Re: T-Junctions re-visited Ben Supnik239March 13, 2013 07:37PM
Re: T-Junctions re-visited Roland Melkert255March 13, 2013 07:59PM
Re: T-Junctions re-visited Ben Supnik276March 13, 2013 08:18PM
Re: T-Junctions re-visited Travis Cobbs300March 14, 2013 03:23PM
Re: T-Junctions re-visited Roland Melkert310March 14, 2013 03:34PM
Re: T-Junctions re-visited Tim Gould323March 14, 2013 03:41PM
Re: T-Junctions re-visited Roland Melkert291March 15, 2013 11:33AM
Re: T-Junctions re-visited Tim Gould251March 13, 2013 07:43PM
Re: T-Junctions re-visited Roland Melkert250March 13, 2013 08:08PM
Re: T-Junctions re-visited Tim Gould251March 13, 2013 08:18PM
Re: T-Junctions re-visited Ben Supnik316March 14, 2013 08:15PM
Re: T-Junctions re-visited Roland Melkert310March 15, 2013 11:29AM
Re: T-Junctions re-visited Travis Cobbs279March 15, 2013 12:27PM
Re: T-Junctions re-visited Ben Supnik293March 15, 2013 05:08PM
Re: T-Junctions re-visited Travis Cobbs278March 16, 2013 11:29PM
Re: T-Junctions re-visited Ben Supnik236March 17, 2013 08:58AM
Re: T-Junctions re-visited Roland Melkert239March 17, 2013 12:35PM
Re: T-Junctions re-visited Travis Cobbs265March 18, 2013 12:28PM
Re: T-Junctions re-visited Travis Cobbs284March 18, 2013 12:32PM
Re: T-Junctions re-visited Roland Melkert276March 18, 2013 05:00PM
Re: T-Junctions re-visited Travis Cobbs308March 18, 2013 11:05PM
Re: T-Junctions re-visited Roland Melkert331March 19, 2013 11:38AM
Re: T-Junctions re-visited Sergio Reano316March 26, 2013 02:46PM
Re: T-Junctions re-visited Roland Melkert267March 27, 2013 11:19AM
Re: T-Junctions re-visited Sergio Reano317March 27, 2013 01:48PM



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