Reversed normal faces

[zeonmastervfx]

I'm not really in search of a solution for a problem, but rather an explanation of an aspect of subdivision modeling. I'm running maya 4 unlimited at school. I have a relatively complex subdivision model, which i modeled half of and then mirrored(not instance). When i attached the two halves, all of the surface normals for the model were reversed. this really isn't a problem, as it can be fixed easily, but does anybody know why this happens?

[jeffd]

It has to do with how mirroring is handled. As I am sure you have noticed, a mirror is achieved by scaling the object to -1.0 along an axis. This essentially turns it inside out. There must be something in Maya that keeps it turned right-side-out in most cases. However, when you freeze transforms or attach objects, this doesn't seem to get handled properly.

This kind of annoys me so I have come to doing one of two things to avoid this. 1) Use Move Component to mirror. Scale to -1 and manually flip the normals. 2) Mirror the object as I normally would, create a cube and do a PolyCombine, then delete the original faces of the cube.

--JeffD

[sibben]

This is handled correctly when using Mirror Geometry. If you mirror manually by scaling and then freezing of course they get flipped. Whenever this happens Maya gives a warning telling you that it has set the display to double sided and/or opposite.

Open the shape node and the Render Stats and uncheck the bottom two boxes, double sided and/or opposite. Then flip.

I find it annoying too. Quite logical but still annoying.

[zeonmastervfx]

hey, thanks a lot. i just used reverse normals to fix the problem, but now i understand why it becomes a problem in the first place.