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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 Cobbs705March 11, 2013 10:38PM
Re: T-Junctions re-visited Tim Gould345March 11, 2013 11:31PM
Re: T-Junctions re-visited Roland Melkert328March 12, 2013 11:17AM
Re: T-Junctions re-visited Ben Supnik329March 12, 2013 11:17AM
Re: T-Junctions re-visited Roland Melkert312March 12, 2013 11:22AM
Re: T-Junctions re-visited Ben Supnik299March 12, 2013 11:32AM
Re: T-Junctions re-visited Roland Melkert298March 12, 2013 11:41AM
Re: T-Junctions re-visited Ben Supnik312March 12, 2013 11:55AM
Re: T-Junctions re-visited Roland Melkert310March 13, 2013 10:08AM
Re: T-Junctions re-visited Travis Cobbs333March 13, 2013 11:27AM
Re: T-Junctions re-visited Allen Smith338March 12, 2013 02:01PM
Re: T-Junctions re-visited Michael Heidemann320March 13, 2013 09:27AM
Re: T-Junctions re-visited Ben Supnik306March 13, 2013 10:37AM
Re: T-Junctions re-visited Tim Gould303March 13, 2013 02:31PM
Re: T-Junctions re-visited Michael Heidemann297March 13, 2013 03:42PM
Re: T-Junctions re-visited Michael Heidemann319March 17, 2013 04:35AM
Re: T-Junctions re-visited Ben Supnik270March 17, 2013 08:43AM
Re: T-Junctions re-visited Michael Heidemann271March 17, 2013 08:59AM
Re: T-Junctions re-visited Ben Supnik276March 17, 2013 09:02AM
Re: T-Junctions re-visited Magnus Forsberg284March 17, 2013 09:15AM
Re: T-Junctions re-visited Travis Cobbs347March 17, 2013 10:09PM
Re: T-Junctions re-visited Ben Supnik307March 18, 2013 07:30AM
Re: T-Junctions re-visited Travis Cobbs307March 18, 2013 10:57AM
Re: T-Junctions re-visited Ben Supnik316March 18, 2013 11:27AM
Re: T-Junctions re-visited Travis Cobbs302March 18, 2013 12:23PM
Re: T-Junctions re-visited Ben Supnik322March 18, 2013 01:41PM
Re: T-Junctions re-visited Roland Melkert337March 18, 2013 02:51PM
Re: T-Junctions re-visited Travis Cobbs307March 18, 2013 02:59PM
Re: T-Junctions re-visited Roland Melkert371March 18, 2013 03:41PM
Re: T-Junctions re-visited Ben Supnik344March 18, 2013 06:09PM
Re: T-Junctions re-visited Roland Melkert319March 19, 2013 11:38AM
Re: T-Junctions re-visited Ben Supnik336March 19, 2013 11:43AM
Re: T-Junctions re-visited Roland Melkert353March 19, 2013 07:07PM
Re: T-Junctions re-visited Travis Cobbs325March 19, 2013 10:13PM
Re: T-Junctions re-visited Tim Gould319March 20, 2013 03:56AM
Re: T-Junctions re-visited Travis Cobbs306March 20, 2013 10:13AM
Re: T-Junctions re-visited Ben Supnik294March 20, 2013 10:23AM
Re: T-Junctions re-visited Travis Cobbs312March 20, 2013 10:29AM
Re: T-Junctions re-visited Travis Cobbs308March 20, 2013 10:26AM
Re: T-Junctions re-visited Ben Supnik286March 20, 2013 11:18AM
Re: T-Junctions re-visited Ben Supnik309March 20, 2013 06:42AM
Re: T-Junctions re-visited Roland Melkert287March 20, 2013 11:36AM
Re: T-Junctions re-visited Philippe Hurbain306March 20, 2013 06:36AM
Re: T-Junctions re-visited Ben Supnik348March 20, 2013 06:58AM
Re: T-Junctions re-visited Allen Smith331March 20, 2013 09:08AM
Re: T-Junctions re-visited Roland Melkert332March 20, 2013 11:35AM
Re: T-Junctions re-visited Ben Supnik742March 20, 2013 11:50AM
Re: T-Junctions re-visited Michael Heidemann337March 18, 2013 03:54PM
Re: T-Junctions re-visited Roland Melkert302March 13, 2013 10:03AM
Re: T-Junctions re-visited Tim Gould274March 13, 2013 03:56PM
Re: T-Junctions re-visited Sergio Reano280March 13, 2013 03:51PM
Re: T-Junctions re-visited Roland Melkert349March 13, 2013 04:36PM
Re: T-Junctions re-visited Tim Gould306March 13, 2013 05:10PM
Re: T-Junctions re-visited Ben Supnik309March 14, 2013 08:17PM
Re: T-Junctions re-visited Tim Gould352March 14, 2013 08:41PM
Re: T-Junctions re-visited Ben Supnik352March 15, 2013 10:56AM
Re: T-Junctions re-visited Roland Melkert298March 15, 2013 11:36AM
Re: T-Junctions re-visited Ben Supnik266March 13, 2013 06:58PM
Re: T-Junctions re-visited Roland Melkert281March 13, 2013 07:27PM
Re: T-Junctions re-visited Ben Supnik263March 13, 2013 07:37PM
Re: T-Junctions re-visited Roland Melkert287March 13, 2013 07:59PM
Re: T-Junctions re-visited Ben Supnik308March 13, 2013 08:18PM
Re: T-Junctions re-visited Travis Cobbs341March 14, 2013 03:23PM
Re: T-Junctions re-visited Roland Melkert353March 14, 2013 03:34PM
Re: T-Junctions re-visited Tim Gould357March 14, 2013 03:41PM
Re: T-Junctions re-visited Roland Melkert337March 15, 2013 11:33AM
Re: T-Junctions re-visited Tim Gould293March 13, 2013 07:43PM
Re: T-Junctions re-visited Roland Melkert285March 13, 2013 08:08PM
Re: T-Junctions re-visited Tim Gould291March 13, 2013 08:18PM
Re: T-Junctions re-visited Ben Supnik359March 14, 2013 08:15PM
Re: T-Junctions re-visited Roland Melkert349March 15, 2013 11:29AM
Re: T-Junctions re-visited Travis Cobbs333March 15, 2013 12:27PM
Re: T-Junctions re-visited Ben Supnik332March 15, 2013 05:08PM
Re: T-Junctions re-visited Travis Cobbs335March 16, 2013 11:29PM
Re: T-Junctions re-visited Ben Supnik265March 17, 2013 08:58AM
Re: T-Junctions re-visited Roland Melkert265March 17, 2013 12:35PM
Re: T-Junctions re-visited Travis Cobbs303March 18, 2013 12:28PM
Re: T-Junctions re-visited Travis Cobbs353March 18, 2013 12:32PM
Re: T-Junctions re-visited Roland Melkert315March 18, 2013 05:00PM
Re: T-Junctions re-visited Travis Cobbs347March 18, 2013 11:05PM
Re: T-Junctions re-visited Roland Melkert382March 19, 2013 11:38AM
Re: T-Junctions re-visited Sergio Reano350March 26, 2013 02:46PM
Re: T-Junctions re-visited Roland Melkert294March 27, 2013 11:19AM
Re: T-Junctions re-visited Sergio Reano362March 27, 2013 01:48PM



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