Hi Skwerm,
> I'd always just turned off "Weld Vertices" because of a
> thread I read back when I started with MoI that said
> Blender really needed it turned off in order to help with
> the vertex normals.
It wasn't really Blender itself that needed it turned off - it was a particular import script that Anthony wrote to import moi-generated LWO files into Blender. That particular script needed welding to be off just because it was easier for him to write that one script that way.
Unfortunately Blender has several other problems with vertex normals aside from ignoring them on OBJ import - when you go to edit mode any existing vertex normals are discarded and recreated from the polygon data, and also when you go to render it also discards them.
Here are a couple of previous discussion threads about it:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4256.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3583.1
There doesn't seem to be very much interest by the Blender devs on fixing up these problems - for example a while back someone opened a bug that any imported vertex normals are discarded if you just go to edit mode and back out again without actually doing anything, and the bug was rejected:
http://projects.blender.org/tracker/?group_id=9&atid=498&func=detail&aid=26405
So for now anyway with all these vertex normal problems Blender is not really very well suited for rendering CAD data compared to other rendering programs.
> My guess is that it's just easier to recalc the vertex normals
> rather than deal with the imported ones.
Sure I guess that's easier but it's also incorrect when the vertex normals in the file are holding information that you can't easily recreate. That's what will happen when the OBJ file was generated from some other original data source than polygons. Like in the case of MoI the normals that are stored in the OBJ file come from the NURBS surface data, so they represent the ideal normal for that point. Since Blender doesn't have access to the original NURBS surface there isn't any way for them to regenerate that exact same data just by trying to average normals from polygon faces.
- Michael |
