T-Junctions re-visited


Re: T-Junctions re-visited
#17
Before going to patch parts definition to avoid T-J gaps, please consider the following:
LDraw part libray is made of recursive parts loading where the position of each of them is determined by a MATRIX.
Even if using the most precise mathematical approach, when you multiply a vertex position by a matrix, some kind of rounding will occour so, even the most precise vertex positioning or the best possible triangle subdivision will cause a gap!

The only way to solve this (and I personally test this with my SR 3DBuilder appl) is to perform a vertex position check at part loading to see if another vertex with the same position (plus a tollerance) has already been loaded, and, if this is the case, then the new vertex will change its coordinates to the already existing one.

This approach has many advantages:
- allows the usage of indexed primitives saving at least 60% of vertex definition
- allows a fast (even if not precise) computation of triangle normals
- comparing the value of the normal for an existing vertex with the normal for the new one let your application decide if a smoothing for the surface must be done or not (ie if the angle between normal is > 45° then avoid smoothing otherwise compute the new normal for the vertex)

The only disadvantage is loading time: I have to cache loaded parts in memory to allow quick model loading...

byes to all

Sergio
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Messages In This Thread
T-Junctions re-visited - by Travis Cobbs - 2013-03-12, 5:38
Re: T-Junctions re-visited - by Tim Gould - 2013-03-12, 6:31
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-12, 18:17
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-12, 18:32
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-12, 18:55
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-13, 18:27
Re: T-Junctions re-visited - by Allen Smith - 2013-03-12, 21:01
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-13, 17:37
Re: T-Junctions re-visited - by Tim Gould - 2013-03-13, 21:31
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-17, 15:43
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-17, 16:02
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-18, 14:30
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-18, 17:57
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-18, 18:27
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-18, 19:23
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-18, 20:41
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-18, 21:59
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-19, 1:09
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-19, 18:43
Re: T-Junctions re-visited - by Tim Gould - 2013-03-20, 10:56
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-20, 17:13
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-20, 17:23
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-20, 17:29
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-20, 17:26
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-20, 18:18
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-20, 13:42
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-20, 13:58
Re: T-Junctions re-visited - by Allen Smith - 2013-03-20, 16:08
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-20, 18:50
Re: T-Junctions re-visited - by Tim Gould - 2013-03-13, 22:56
Re: T-Junctions re-visited - by Sergio Reano - 2013-03-13, 22:51
Re: T-Junctions re-visited - by Tim Gould - 2013-03-14, 0:10
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-15, 3:17
Re: T-Junctions re-visited - by Tim Gould - 2013-03-15, 3:41
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-15, 17:56
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-14, 1:58
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-14, 2:37
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-14, 3:18
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-14, 22:23
Re: T-Junctions re-visited - by Tim Gould - 2013-03-14, 22:41
Re: T-Junctions re-visited - by Tim Gould - 2013-03-14, 2:43
Re: T-Junctions re-visited - by Tim Gould - 2013-03-14, 3:18
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-15, 3:15
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-15, 19:27
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-16, 0:08
Re: T-Junctions re-visited - by Ben Supnik - 2013-03-17, 15:58
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-18, 19:28
Re: T-Junctions re-visited - by Travis Cobbs - 2013-03-18, 19:32
Re: T-Junctions re-visited - by Sergio Reano - 2013-03-26, 21:46
Re: T-Junctions re-visited - by Sergio Reano - 2013-03-27, 20:48

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