Normals 101 - Back to basics

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  04 April 2013
Normals 101 - Back to basics

Hey guys, I need help straightening the world of normals out. I am on Maya2013 and Vray if the answers are slightly more specific but here goes.

I used to think normals were basic. Basically it is a tangent that defines the surface direction. Any issues, flip it should work.

Well I have a complicated model and i've been trying to split it into little segments. Along those areas when extracted. There are artifacts.

Yesterday night. I solved it by running "Average Normals". But between Vertex Normal, Lock Normals, Unlock Normals, Set Normal Angle and Soften & Harden edge. I think i'm lost.

Not to mention the help files kinda just repeats the question.

Quote: Normalize before averaging
Turn this option on so that all the normals in the calculation have a length of 1, and each one contributes equally to the average. This is the default setting.

If this option is turned off, and if you explicitly set normals where the length is not equal to 1, then the contribution of these normals to the average is weighted by the length of the normal (the new normal will be closer in direction to the longer normals).

Normalize after averaging
If Normalize before averaging is off, you can keep the length of the normal that resulted from the calculation, or set the length to 1 by turning on Normalize after averaging. The length may be significant in future invocations of Average Normals. If Normalize before averaging is on, this option is disabled, since the result will be automatically normalized.

Do not normalize
Turn on Do not normalize when you do not want the Normals normalized before averaging.
Grouping threshold

The vertices within the distance you specify are considered as a group to share a normal which is the average of the normals in the group. So your selected vertices may be divided into several groups, and each group averaged separately.
Allow zero normals

If two normals of exactly opposite direction are averaged, the result will be a zero-length normal. While this is valid in Maya, it may not be what you want. If this option is turned off, the normals are replaced by user-specified value (see below).

Replace zero normals by
If Allow Zero Normals is on, this option is disabled. If Allow Zero Normals is off, the normals are replaced by the X, Y, and Z values you specify here.

Essentially, I need to know more about this for production work with realistic models, what is the correct workflow? Are normals ever supposed to be set at 0 or the default and for good reason, should be 30.

If it is 0, what are the issues? And what if my model has been smoothed 3 times? Does normals matter then? Also, vertex normals?

My current situation that resulted in this post was that I have a model of a controller and I need to use the "Project curve on mesh" followed by "Split mesh according to curve" tools. This worked but the seams have some wonky artifacting. Yesterday, my tests worked. Today, it doesn't. I thought I needed to unlock my normals but either way I am confused with the concepts now.

Please help. Love your advice everyone. Thanks.
  04 April 2013
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