Normal Reversal

[pramodcb]

I want to use mel script to check and correct the face normals that are wrong. Everybody know closed volumns face normals is outward. If have face normals is inward, how to know that and how to correct it.

I just know the "ConformPolygonNormals" of command to conform normals. but it just modify normals dirction to what they are almost in ...

How to do it?
Thank you

[isam]

you culd conform and then flip, but if u want it totally scripted, id say query the angle of the normals, and check if the average angles is less than or more than a 180, and flip or dont accordingly,

[pramodcb]

QUOTE(isam @ 09/26/07, 05:43 PM) [snapback]273887[/snapback]
you culd conform and then flip, but if u want it totally scripted, id say query the angle of the normals, and check if the average angles is less than or more than a 180, and flip or dont accordingly,

Hello
thank you for ur reply actually we had our exams , so we could not get back to you
now we restarted the work actually we tried finding out using dot product of polynormalvertex i.e dot product of standard vector to the obtained result but we could not find it out any ways ill let u know after we worked on it
Do u know how conform works(back end of conform) may be by this we can get the solution
and one more thing what u told is seems to be right but do you have detail code
thank you

[joojaa]

Conform selects a face, reads in it winding order, then goes face by face outwards form that face point and makes sure the next face has the same winding direction(it then repeats thei for each subshell separately, offocurse the result for each subshell is a bit of a gamble). This produces what your after if:

Your object is actually one piece

Of not then your in trouble. Because theres actualy no way of ensuring it builds up a real volume. And because of that you may need to guess and this makes it a bit error prone. However if you ray trace from the face out and get a odd number of hits your pointing outwards if a even your pointing inwards. (off course again this assumes your shape is closed, in which case conform SHOULD have worked fine, or at least so all faces have same alinement's per sub shell so you can trace only one face)

It so happens you cant do thsi to unclosed surfaces very well.