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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 Cobbs761March 11, 2013 10:38PM
Re: T-Junctions re-visited Tim Gould375March 11, 2013 11:31PM
Re: T-Junctions re-visited Roland Melkert356March 12, 2013 11:17AM
Re: T-Junctions re-visited Ben Supnik376March 12, 2013 11:17AM
Re: T-Junctions re-visited Roland Melkert347March 12, 2013 11:22AM
Re: T-Junctions re-visited Ben Supnik335March 12, 2013 11:32AM
Re: T-Junctions re-visited Roland Melkert327March 12, 2013 11:41AM
Re: T-Junctions re-visited Ben Supnik335March 12, 2013 11:55AM
Re: T-Junctions re-visited Roland Melkert329March 13, 2013 10:08AM
Re: T-Junctions re-visited Travis Cobbs357March 13, 2013 11:27AM
Re: T-Junctions re-visited Allen Smith363March 12, 2013 02:01PM
Re: T-Junctions re-visited Michael Heidemann351March 13, 2013 09:27AM
Re: T-Junctions re-visited Ben Supnik333March 13, 2013 10:37AM
Re: T-Junctions re-visited Tim Gould334March 13, 2013 02:31PM
Re: T-Junctions re-visited Michael Heidemann321March 13, 2013 03:42PM
Re: T-Junctions re-visited Michael Heidemann360March 17, 2013 04:35AM
Re: T-Junctions re-visited Ben Supnik295March 17, 2013 08:43AM
Re: T-Junctions re-visited Michael Heidemann285March 17, 2013 08:59AM
Re: T-Junctions re-visited Ben Supnik290March 17, 2013 09:02AM
Re: T-Junctions re-visited Magnus Forsberg316March 17, 2013 09:15AM
Re: T-Junctions re-visited Travis Cobbs366March 17, 2013 10:09PM
Re: T-Junctions re-visited Ben Supnik333March 18, 2013 07:30AM
Re: T-Junctions re-visited Travis Cobbs326March 18, 2013 10:57AM
Re: T-Junctions re-visited Ben Supnik331March 18, 2013 11:27AM
Re: T-Junctions re-visited Travis Cobbs323March 18, 2013 12:23PM
Re: T-Junctions re-visited Ben Supnik346March 18, 2013 01:41PM
Re: T-Junctions re-visited Roland Melkert372March 18, 2013 02:51PM
Re: T-Junctions re-visited Travis Cobbs345March 18, 2013 02:59PM
Re: T-Junctions re-visited Roland Melkert415March 18, 2013 03:41PM
Re: T-Junctions re-visited Ben Supnik383March 18, 2013 06:09PM
Re: T-Junctions re-visited Roland Melkert335March 19, 2013 11:38AM
Re: T-Junctions re-visited Ben Supnik355March 19, 2013 11:43AM
Re: T-Junctions re-visited Roland Melkert382March 19, 2013 07:07PM
Re: T-Junctions re-visited Travis Cobbs351March 19, 2013 10:13PM
Re: T-Junctions re-visited Tim Gould342March 20, 2013 03:56AM
Re: T-Junctions re-visited Travis Cobbs328March 20, 2013 10:13AM
Re: T-Junctions re-visited Ben Supnik315March 20, 2013 10:23AM
Re: T-Junctions re-visited Travis Cobbs351March 20, 2013 10:29AM
Re: T-Junctions re-visited Travis Cobbs324March 20, 2013 10:26AM
Re: T-Junctions re-visited Ben Supnik309March 20, 2013 11:18AM
Re: T-Junctions re-visited Ben Supnik344March 20, 2013 06:42AM
Re: T-Junctions re-visited Roland Melkert307March 20, 2013 11:36AM
Re: T-Junctions re-visited Philippe Hurbain345March 20, 2013 06:36AM
Re: T-Junctions re-visited Ben Supnik391March 20, 2013 06:58AM
Re: T-Junctions re-visited Allen Smith366March 20, 2013 09:08AM
Re: T-Junctions re-visited Roland Melkert394March 20, 2013 11:35AM
Re: T-Junctions re-visited Ben Supnik806March 20, 2013 11:50AM
Re: T-Junctions re-visited Michael Heidemann383March 18, 2013 03:54PM
Re: T-Junctions re-visited Roland Melkert336March 13, 2013 10:03AM
Re: T-Junctions re-visited Tim Gould304March 13, 2013 03:56PM
Re: T-Junctions re-visited Sergio Reano295March 13, 2013 03:51PM
Re: T-Junctions re-visited Roland Melkert375March 13, 2013 04:36PM
Re: T-Junctions re-visited Tim Gould324March 13, 2013 05:10PM
Re: T-Junctions re-visited Ben Supnik348March 14, 2013 08:17PM
Re: T-Junctions re-visited Tim Gould391March 14, 2013 08:41PM
Re: T-Junctions re-visited Ben Supnik390March 15, 2013 10:56AM
Re: T-Junctions re-visited Roland Melkert332March 15, 2013 11:36AM
Re: T-Junctions re-visited Ben Supnik292March 13, 2013 06:58PM
Re: T-Junctions re-visited Roland Melkert301March 13, 2013 07:27PM
Re: T-Junctions re-visited Ben Supnik295March 13, 2013 07:37PM
Re: T-Junctions re-visited Roland Melkert321March 13, 2013 07:59PM
Re: T-Junctions re-visited Ben Supnik323March 13, 2013 08:18PM
Re: T-Junctions re-visited Travis Cobbs393March 14, 2013 03:23PM
Re: T-Junctions re-visited Roland Melkert399March 14, 2013 03:34PM
Re: T-Junctions re-visited Tim Gould377March 14, 2013 03:41PM
Re: T-Junctions re-visited Roland Melkert380March 15, 2013 11:33AM
Re: T-Junctions re-visited Tim Gould338March 13, 2013 07:43PM
Re: T-Junctions re-visited Roland Melkert299March 13, 2013 08:08PM
Re: T-Junctions re-visited Tim Gould322March 13, 2013 08:18PM
Re: T-Junctions re-visited Ben Supnik386March 14, 2013 08:15PM
Re: T-Junctions re-visited Roland Melkert385March 15, 2013 11:29AM
Re: T-Junctions re-visited Travis Cobbs362March 15, 2013 12:27PM
Re: T-Junctions re-visited Ben Supnik350March 15, 2013 05:08PM
Re: T-Junctions re-visited Travis Cobbs371March 16, 2013 11:29PM
Re: T-Junctions re-visited Ben Supnik282March 17, 2013 08:58AM
Re: T-Junctions re-visited Roland Melkert283March 17, 2013 12:35PM
Re: T-Junctions re-visited Travis Cobbs324March 18, 2013 12:28PM
Re: T-Junctions re-visited Travis Cobbs393March 18, 2013 12:32PM
Re: T-Junctions re-visited Roland Melkert350March 18, 2013 05:00PM
Re: T-Junctions re-visited Travis Cobbs372March 18, 2013 11:05PM
Re: T-Junctions re-visited Roland Melkert425March 19, 2013 11:38AM
Re: T-Junctions re-visited Sergio Reano364March 26, 2013 02:46PM
Re: T-Junctions re-visited Roland Melkert314March 27, 2013 11:19AM
Re: T-Junctions re-visited Sergio Reano405March 27, 2013 01:48PM



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