fixing polygon normals

[s...@weacceptyou.com]

Hello,

im trying to write a bit of python code which will do a check at any given time that all the polygon surfaces in my scene have normals pointing outwards.

obviously with flat surfaces there is no way for python to know which direction is correct for the normals to be. But im talking about the concave surfaces or closed surfaces. I want the normals to always be facing outwards.

is there a way through python to check this automatically and reverse normals, without having to check each surface manually.

thanks,
Sam

[Demetrius]

Just a thought- could you reconstruct the normal by using the UV directions on the polys?

Demetrius Leal

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[Michael Boon]

What about the command polyNormal(normalMode=2) (or in the Maya GUI, Normals > Conform)? If your problem is just a few faces in each mesh, that would probably take care of it for you.

If your problem is entire meshes being inside out and you're looking for an algorithm to find out which ones are inside out, I'd look at computePolysetVolume.mel (included with Maya). If you do a calculation like that on a mesh, and the result comes out negative, then the mesh is inside-out.

I hope that's useful.

Boon