View Full Version : The black dot mystery -> maya skincluster vertex normals

05 May 2007, 12:59 PM
Hiya, since I just have the case and I wondered the same thing again.

Sometimes when dealing with skinclusters & painting weights, one of the vertices (the surrounding faces) turns black (due to some vertex normal fliping caused by weight painting for some strange reason).
A lot of times this is due to really small weights (<0.01) and can be corrected with prune weights. Now that I m having that issue again I looked into it a bit more as it s not due to small weights this time....
Does anyone know what this is caused by and how to avoid it, generally speaking ?
Cos when I look it right now, the vertices in question don t have a vertex normal anymore, or at least there s no visible normal at all......!?
And when copying weights onto a "clean" mesh, the normals get weird again and receive total values of 0 0 0 0 0 0 0 0 0 0 0 0 ... (polyNormalPerVertex -q -xyz) = wtf ? any ideas ? why does the painting tool alter the vertex normals at all ? and how can it be avoided ?


05 May 2007, 03:12 PM
Are all your normals pointing in the same direction before skinning? Usually when I get a model I make sure that all normals are set to face, you'll know right away when you start skinning that your normals are bad if you start getting black faceting. I know here we make our modeling department do a Set To Face, Soften Normals and then just delete history before passing downstream to rigging.

Try setting to face and then painting, see if it helps some and let me know if there's any other issues.


05 May 2007, 04:45 PM
Damn cgtalk maintenance, just typed an answer & submitted when it died...

Hi Shawn,
I allways do a set to face & average/smooth before I start weighting, so that can t be the issue....
And the weird thing was that the normal overwrite to 0 appeared suddenly while painting on the mesh which I allready worked on for quite a bit....
I thought this might be due to the average normals I used on that model before skinning, so I tried to exchange it with a smooth edge version instead.... which gave me the same issues...when I copied the weights....

I just tested other copy weight procedures, and the problem seems to be maya7s copy weight function which transfers the normal flip to 0 forced by painting weights onto the target mesh as well.... when I manually flip a normal of a skinned vert it doesn t get copied by maya7s "copy skin weights" function...also other procedures to transfer weights don't seem to store / transfer vertex normal information at all whether they be done by hand or by accident via weight painting....
But this stil leaves the question why on earth the paint weight tool sometimes alters vertex normals...

But nevermind, I can get rid of it by using other weight copy functions....


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05 May 2007, 04:45 PM
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