Hi Skwerm, also see this thread on the Blender artists forum that talks about the problem with the Blender importer ignoring the vertex normal data:

http://blenderartists.org/forum/showthread.php?182195-OBJ-import-normals

- Michael

<< I'm curious about why MoI export to OBJ (and perhaps other formats, I haven't checked) includes duplicate vertices. I was reading another thread here about Octane having problems rendering MoI output and the subject came up about duplicate vertices.>>

I don't think that the duplicate vertices in that case were due to a seam from MoI (since the duplicates are all over the place and not just on a seam). It was just due to a very sloppy mesh. That is why I doubted that the mesh came from MoI, since I have never seen MoI create random duplicate vertices all around the mesh. If you want to take a look at that mesh yourself, you can find it here: http://refractivesoftware.com/forum/download/file.php?id=10501

<< The question then becomes "why isnt Octane or Blender reading the true vertex normals from the obj file and screwing up the shading??

This question is for Blender or Octane though, not MoI.>>

Octane doesn't have a problem reading in normals from MoI.

Blender ignores normal information and calculates its own (which ends up messing up renders from MoI).

Sorry YHWH,
I didnt mean to insinuate anything about Octane. I was just responding to the OP and how it's not a question about MoI....

Thanks everyone for all the help!

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. I hadn't "put two and two together," so to speak, and realized that this was where my current question was originating from.

I'll see what I can do about getting the developer for the OBJ import for Blender to address this problem. If nothing else, I'd like an answer as to why they're being ignored. My guess is that it's just easier to recalc the vertex normals rather than deal with the imported ones.

Cheers!

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