Wrong mirror with face-duplication #37820

New Issue

Karja Krähwald · 2013-12-14T22:24:10+01:00

Karja Krähwald commented

2013-12-14 22:24:10 +01:00

System Information
Windows 7 64, HD 5770

Blender Version
Broken: 2.69 release & "buildbot hash: ff6bf13 (2013-12-14/00:42)"

Short description of error
Objects that use face-duplication get a wrong rotation on the mirror (mirror-modifier).

Exact steps for others to reproduce the error
Duplication_Mirror.blend

Add a plane and give it an array (higher count to see it better) and a mirror modifier.
Add a monkey (Suzanne) and parent it to the plane.
Select plane, go to "Properties">"Object">"Duplication" and activate "Faces".

The monkeys on the mirrored side pointing in a different direction.

**System Information** Windows 7 64, HD 5770 **Blender Version** Broken: 2.69 release & "buildbot hash: ff6bf13 (2013-12-14/00:42)" **Short description of error** Objects that use face-duplication get a wrong rotation on the mirror (mirror-modifier). **Exact steps for others to reproduce the error** [Duplication_Mirror.blend](https://archive.blender.org/developer/F41130/Duplication_Mirror.blend) 1. Add a plane and give it an array (higher count to see it better) and a mirror modifier. 2. Add a monkey (Suzanne) and parent it to the plane. 3. Select plane, go to "Properties">"Object">"Duplication" and activate "Faces". The monkeys on the mirrored side pointing in a different direction.

Karja Krähwald commented

2013-12-14 22:24:10 +01:00

Changed status to: 'Open'

Karja Krähwald commented

2013-12-14 22:24:10 +01:00

Added subscriber: @karja

Brecht Van Lommel commented

2013-12-16 11:55:20 +01:00

Added subscriber: @brecht

Brecht Van Lommel commented

2013-12-16 11:55:20 +01:00

Developer note:

The vertex order in the face is switched to avoid the normal pointing in the wrong direction. If we don't flip the normal the object would be on the wrong side of the face. For the simple square in this .blend file the vertex order could be changed so the result matches, but for arbitrary quads or polygons it's not actually possible.

The only solution I can think of would be to flag face as being flipped, so that the dupliface code can check that and use the opposite vertex order while still keeping the object on the same side of the face. That would be a mirror modifier + dupliface specific hack though, not sure we want to do it. Maybe someone can think of a better solution, but as far as I can tell a bare mesh does not actually provide enough information to give the expected result here.

Developer note: The vertex order in the face is switched to avoid the normal pointing in the wrong direction. If we don't flip the normal the object would be on the wrong side of the face. For the simple square in this .blend file the vertex order could be changed so the result matches, but for arbitrary quads or polygons it's not actually possible. The only solution I can think of would be to flag face as being flipped, so that the dupliface code can check that and use the opposite vertex order while still keeping the object on the same side of the face. That would be a mirror modifier + dupliface specific hack though, not sure we want to do it. Maybe someone can think of a better solution, but as far as I can tell a bare mesh does not actually provide enough information to give the expected result here.

Brecht Van Lommel commented

2013-12-18 11:04:04 +01:00

Thinking about this more, I'm going to move this to the To Do list, it would be nice if this worked but it shouldn't be considered a bug:
http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#DupliObject

Thinking about this more, I'm going to move this to the To Do list, it would be nice if this worked but it shouldn't be considered a bug: http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#DupliObject

Brecht Van Lommel commented

2013-12-18 11:04:11 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2013-12-18 11:04:11 +01:00

Brecht Van Lommel self-assigned this 2013-12-18 11:04:11 +01:00

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Wrong mirror with face-duplication #37820