How to know the normal of a plane?

How can I calculate the normal vector of a plane?

For example this plane:

v[1] ±----------+ v[0]
| |
| |
| x |
| |
| |
v[2] ±----------+ v[3]

If you know 2 vectors that lie within the plane which can be easily calculated from 3 points lying within the plane, you can use the cross product to calculate a vector normal to both. Right hand rule applies.

Hopefully, you know what a cross product is.


for your example given (next time put your ASCII art in CODE tags!) the normal for the plane is:

N = (v[1] - v[0]) X (v[2] - v[0])

where X is the cross product; <— EDIT: gotta love the semi-colon at the end of a sentence. don’t know how many times i’ve done that!


[This message has been edited by jebus (edited 01-20-2003).]