# Difference between revisions of "Calculating a Surface Normal"

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A surface normal for a triangle can be calculated by taking the vector cross product of two edges of that triangle. The order of the vertices used in the calculation witt affect the direction of the normal (in or out of the face w.r.t. winding). | A surface normal for a triangle can be calculated by taking the vector cross product of two edges of that triangle. The order of the vertices used in the calculation witt affect the direction of the normal (in or out of the face w.r.t. winding). | ||

− | So for a triangle p1, p2, p3, if the vector U = p2 - p1 and the vector V = p3-p1 then the normal U X V | + | So for a triangle p1, p2, p3, if the vector U = p2 - p1 and the vector V = p3 - p1 then the normal N = U X V and can be calculated by: |

Nx = UyVz - UzVy | Nx = UyVz - UzVy |

## Revision as of 07:24, 5 April 2006

A surface normal for a triangle can be calculated by taking the vector cross product of two edges of that triangle. The order of the vertices used in the calculation witt affect the direction of the normal (in or out of the face w.r.t. winding).

So for a triangle p1, p2, p3, if the vector U = p2 - p1 and the vector V = p3 - p1 then the normal N = U X V and can be calculated by:

Nx = UyVz - UzVy

Ny = UzVx - UxVz

Nz = UxVy - UyVx