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# plane normals n stuff

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ArchMiffo    122
Well, the search function is down and I can''t find what I''m looking for on the net so I have to ask here. Ok, I have a block, 8 corners and 6 faces (like a dice but with iregular quads). Now I want to find out how to calculate the normal för each face of the block. I know the origin and the corners coordinates. If anyone care to explain or point me to a site where it is explained in plain english (swedish will do as well), that would be nice. Thanks

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ArchMiffo    122
So if A,B and C are 3D-coordinates that would be something like this: (A.x*B.x, A.y*B.y, A.z*B.z) * (A.x*C.x, A.y*C.y, A.z*C.z), correct?

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Guest Anonymous Poster
No, AB means the vector (b.x-a.x, b.y-a.y, b.z-a.z) and x denotes the vector product.

ArchMiffo    122
Strange notation

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Guest Anonymous Poster
quote:
Original post by Anonymous Poster
No, AB means the vector (b.x-a.x, b.y-a.y, b.z-a.z) and x denotes the vector product.

The cross product actually (If U want the normal).
A x B would be (C):
C.x = A.y*B.z - A.z*B.y
C.y = A.z*B.x - A.x*B.z
C.z = A.x*B.y - A.y*B.x
C is the result vector (the normal); it''s peripendicular to A and B.

I hope I remember it correctly...

p.s. is the normal faces the wrong way swap A and B.

see amir.cfxweb.net