# Formula for Vertex Normals?

Hi,

So COLLADA files are made up of triangles. If a face normal is a 90 degree angle from the face of each triangle, how does one compute that value for each triangle in a COLLADA file. Does anyone know how to do it in Objective-C, if all of the mesh vertices (X, Y, Z values) are in an NSMutableArray? To further specify, I have all the mesh vertices grouped together as (X, Y, Z) and they are stored in an NSMutableArray. The arrays can get quite large, sometimes over 2 million objects. It’s still workable though and relatively fast.

Also, I not doing this in a graphical context, I am more referring to a mathematical context. I feel like this is standard TRIGONOMETRY but again I may be wrong. I need an ANGLE, corresponding to a HORIZONTAL or VERTICAL value. So, if the part is laid down HORIZONTALLY, and a triangle is at a 38 degree angle, how would I know that if I only have an (X, Y, and Z value) representing a triangle in space?

Example…

if

TRIANGLE VALUES = (X 3.5678543,Y 7.65432, Z 19.78965)

then

VERTEX NORMAL ANGLE = ???

Also, if someone wants to help me take a crack at it, here is a wiki…

http://en.wikipedia.org/wiki/Normal_(geometry)