Over the last years I’ve noticed that there is
a persistent bug that exists either in the FBX import or the UV lightpacker.
This bug creates extra line segments, that takes up extra space as seen in my example below.
These lines will sometimes take up as much as 50 % of the lightmap resolution.
(As seen in my example below)
These bugs show up on exports from both 3dsMax and Blender.
Steps to reproduce:
These bugs most often occur if you have a UVWuwrap modifier that is further down in your stack.
If you add a new modifier on topp of your stack and just move your UV islands a tiny bit, the bug can go away.
(Also if you press “relax” on your UV island the bug can go away)
Zbrush have a similar bug where UV islands with vertices that are 100% overlapping (Like on a cut seam)
will get wielded if not moved slightly.
This behaviour from Zbrush do not accur in Unreal exports,
but it does however lead me to believe that this is a similar issue where the importer is displaying unwanted behaviour.
This issue is fairly rampant. so it should be easy to reproduce.
My 3d studio Max scene units are in centimeters and my Blender scenes are in Meters.
(They both exhibit this bugged behaviour)