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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 Cobbs799March 11, 2013 10:38PM
Re: T-Junctions re-visited Tim Gould403March 11, 2013 11:31PM
Re: T-Junctions re-visited Roland Melkert375March 12, 2013 11:17AM
Re: T-Junctions re-visited Ben Supnik393March 12, 2013 11:17AM
Re: T-Junctions re-visited Roland Melkert361March 12, 2013 11:22AM
Re: T-Junctions re-visited Ben Supnik349March 12, 2013 11:32AM
Re: T-Junctions re-visited Roland Melkert340March 12, 2013 11:41AM
Re: T-Junctions re-visited Ben Supnik351March 12, 2013 11:55AM
Re: T-Junctions re-visited Roland Melkert347March 13, 2013 10:08AM
Re: T-Junctions re-visited Travis Cobbs370March 13, 2013 11:27AM
Re: T-Junctions re-visited Allen Smith379March 12, 2013 02:01PM
Re: T-Junctions re-visited Michael Heidemann366March 13, 2013 09:27AM
Re: T-Junctions re-visited Ben Supnik352March 13, 2013 10:37AM
Re: T-Junctions re-visited Tim Gould352March 13, 2013 02:31PM
Re: T-Junctions re-visited Michael Heidemann337March 13, 2013 03:42PM
Re: T-Junctions re-visited Michael Heidemann373March 17, 2013 04:35AM
Re: T-Junctions re-visited Ben Supnik308March 17, 2013 08:43AM
Re: T-Junctions re-visited Michael Heidemann308March 17, 2013 08:59AM
Re: T-Junctions re-visited Ben Supnik302March 17, 2013 09:02AM
Re: T-Junctions re-visited Magnus Forsberg327March 17, 2013 09:15AM
Re: T-Junctions re-visited Travis Cobbs382March 17, 2013 10:09PM
Re: T-Junctions re-visited Ben Supnik347March 18, 2013 07:30AM
Re: T-Junctions re-visited Travis Cobbs338March 18, 2013 10:57AM
Re: T-Junctions re-visited Ben Supnik348March 18, 2013 11:27AM
Re: T-Junctions re-visited Travis Cobbs338March 18, 2013 12:23PM
Re: T-Junctions re-visited Ben Supnik375March 18, 2013 01:41PM
Re: T-Junctions re-visited Roland Melkert395March 18, 2013 02:51PM
Re: T-Junctions re-visited Travis Cobbs366March 18, 2013 02:59PM
Re: T-Junctions re-visited Roland Melkert433March 18, 2013 03:41PM
Re: T-Junctions re-visited Ben Supnik405March 18, 2013 06:09PM
Re: T-Junctions re-visited Roland Melkert359March 19, 2013 11:38AM
Re: T-Junctions re-visited Ben Supnik379March 19, 2013 11:43AM
Re: T-Junctions re-visited Roland Melkert401March 19, 2013 07:07PM
Re: T-Junctions re-visited Travis Cobbs373March 19, 2013 10:13PM
Re: T-Junctions re-visited Tim Gould376March 20, 2013 03:56AM
Re: T-Junctions re-visited Travis Cobbs344March 20, 2013 10:13AM
Re: T-Junctions re-visited Ben Supnik338March 20, 2013 10:23AM
Re: T-Junctions re-visited Travis Cobbs365March 20, 2013 10:29AM
Re: T-Junctions re-visited Travis Cobbs344March 20, 2013 10:26AM
Re: T-Junctions re-visited Ben Supnik327March 20, 2013 11:18AM
Re: T-Junctions re-visited Ben Supnik364March 20, 2013 06:42AM
Re: T-Junctions re-visited Roland Melkert325March 20, 2013 11:36AM
Re: T-Junctions re-visited Philippe Hurbain360March 20, 2013 06:36AM
Re: T-Junctions re-visited Ben Supnik407March 20, 2013 06:58AM
Re: T-Junctions re-visited Allen Smith387March 20, 2013 09:08AM
Re: T-Junctions re-visited Roland Melkert426March 20, 2013 11:35AM
Re: T-Junctions re-visited Ben Supnik849March 20, 2013 11:50AM
Re: T-Junctions re-visited Michael Heidemann399March 18, 2013 03:54PM
Re: T-Junctions re-visited Roland Melkert354March 13, 2013 10:03AM
Re: T-Junctions re-visited Tim Gould320March 13, 2013 03:56PM
Re: T-Junctions re-visited Sergio Reano311March 13, 2013 03:51PM
Re: T-Junctions re-visited Roland Melkert389March 13, 2013 04:36PM
Re: T-Junctions re-visited Tim Gould338March 13, 2013 05:10PM
Re: T-Junctions re-visited Ben Supnik366March 14, 2013 08:17PM
Re: T-Junctions re-visited Tim Gould413March 14, 2013 08:41PM
Re: T-Junctions re-visited Ben Supnik407March 15, 2013 10:56AM
Re: T-Junctions re-visited Roland Melkert355March 15, 2013 11:36AM
Re: T-Junctions re-visited Ben Supnik306March 13, 2013 06:58PM
Re: T-Junctions re-visited Roland Melkert317March 13, 2013 07:27PM
Re: T-Junctions re-visited Ben Supnik312March 13, 2013 07:37PM
Re: T-Junctions re-visited Roland Melkert337March 13, 2013 07:59PM
Re: T-Junctions re-visited Ben Supnik339March 13, 2013 08:18PM
Re: T-Junctions re-visited Travis Cobbs405March 14, 2013 03:23PM
Re: T-Junctions re-visited Roland Melkert418March 14, 2013 03:34PM
Re: T-Junctions re-visited Tim Gould399March 14, 2013 03:41PM
Re: T-Junctions re-visited Roland Melkert404March 15, 2013 11:33AM
Re: T-Junctions re-visited Tim Gould351March 13, 2013 07:43PM
Re: T-Junctions re-visited Roland Melkert319March 13, 2013 08:08PM
Re: T-Junctions re-visited Tim Gould340March 13, 2013 08:18PM
Re: T-Junctions re-visited Ben Supnik405March 14, 2013 08:15PM
Re: T-Junctions re-visited Roland Melkert395March 15, 2013 11:29AM
Re: T-Junctions re-visited Travis Cobbs378March 15, 2013 12:27PM
Re: T-Junctions re-visited Ben Supnik364March 15, 2013 05:08PM
Re: T-Junctions re-visited Travis Cobbs387March 16, 2013 11:29PM
Re: T-Junctions re-visited Ben Supnik293March 17, 2013 08:58AM
Re: T-Junctions re-visited Roland Melkert294March 17, 2013 12:35PM
Re: T-Junctions re-visited Travis Cobbs339March 18, 2013 12:28PM
Re: T-Junctions re-visited Travis Cobbs413March 18, 2013 12:32PM
Re: T-Junctions re-visited Roland Melkert365March 18, 2013 05:00PM
Re: T-Junctions re-visited Travis Cobbs392March 18, 2013 11:05PM
Re: T-Junctions re-visited Roland Melkert445March 19, 2013 11:38AM
Re: T-Junctions re-visited Sergio Reano389March 26, 2013 02:46PM
Re: T-Junctions re-visited Roland Melkert331March 27, 2013 11:19AM
Re: T-Junctions re-visited Sergio Reano428March 27, 2013 01:48PM



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