Unwrap creates stray faces #31145

New Issue

Reiner Prokein · 2012-04-28T13:35:39+02:00

Reiner Prokein commented

2012-04-28 13:35:39 +02:00

%%%r46007 Win 7, 64 Bit

Wnen i unwrap my mesh then i get unexpected results in both modes, angle based and conformal. Some vertices or edges in the middle of the uv patches gets disorted to other uv patches, without having a seam at all. Which produces large stray faces. See screenshot.%%%

%%%r46007 Win 7, 64 Bit Wnen i unwrap my mesh then i get unexpected results in both modes, angle based and conformal. Some vertices or edges in the middle of the uv patches gets disorted to other uv patches, without having a seam at all. Which produces large stray faces. See screenshot.%%%

Reiner Prokein commented

2012-04-28 13:35:39 +02:00

Changed status to: 'Open'

Reiner Prokein commented

2012-04-28 19:49:31 +02:00

%%%I´ve investigated this one a bit further, have isolated one of those trouble faces, and stumbled across a geometry problem. In trueSpace the geometry is a quad. It acts as a quad, and it shows as a quad. I can look at all four corners of the face in solid mode from the top and from the bottom, even when it`s a bit odd disorted. In Blender it shows as a quad from the backside. But as a tri from the top side. And i cannot have a look at all four vertexes here in solid mode.

There is most probably the underlying triangulation having a party at this special geometry. At the top it`s a quad that is not connected with the neighbour face. But the underlying edge of the tri is paired up with the neighbour face, telling Blender that this is the neighbour edge. And this seems to be the cause for the unwrapping problem then too. The by that problem hidden tri gets a special therapy, and gets isolated. Which creates this stray face then.

This geometry was created by blender by the way, using the Decimate modifier.

I´ve added two more screenshots and a reduced example. The face in question is red marked.%%%

%%%I´ve investigated this one a bit further, have isolated one of those trouble faces, and stumbled across a geometry problem. In trueSpace the geometry is a quad. It acts as a quad, and it shows as a quad. I can look at all four corners of the face in solid mode from the top and from the bottom, even when it`s a bit odd disorted. In Blender it shows as a quad from the backside. But as a tri from the top side. And i cannot have a look at all four vertexes here in solid mode. There is most probably the underlying triangulation having a party at this special geometry. At the top it`s a quad that is not connected with the neighbour face. But the underlying edge of the tri is paired up with the neighbour face, telling Blender that this is the neighbour edge. And this seems to be the cause for the unwrapping problem then too. The by that problem hidden tri gets a special therapy, and gets isolated. Which creates this stray face then. This geometry was created by blender by the way, using the Decimate modifier. I´ve added two more screenshots and a reduced example. The face in question is red marked.%%%

Brecht Van Lommel commented

2012-05-01 20:24:19 +02:00

%%%This is some really strange geometry. The problem seems to be that the uv unwrapper is splitting this quad in two triangles, but the uv coordinates are still shared, so the quad is actually part of two islands.%%%

Ton Roosendaal commented

2013-02-16 17:11:25 +01:00

%%%Brecht: can we mark this down in wiki docs as "known limitation" ?%%%

Brecht Van Lommel commented

2013-02-17 15:30:06 +01:00

%%%Yes, I've tried to fix this a few times but it doesn't fit the design well, it's also very uncommon to have this kind of topology anyway, so moved to todo:
http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#UV_Unwrapping%%%

%%%Yes, I've tried to fix this a few times but it doesn't fit the design well, it's also very uncommon to have this kind of topology anyway, so moved to todo: http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#UV_Unwrapping%%%

Brecht Van Lommel commented

2013-02-17 15:30:06 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2013-02-17 15:30:06 +01:00

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Unwrap creates stray faces #31145