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# Vectors on a plane

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I have a vector which is a point on a plane, and I have the planes normal. Now I need to compute the 4 vectors (or points in space) for a coplanar flat box face that is 16x16 units in size spaced around the center vector. Any ideas how to do the match for this? [edited by - quantum_red on August 14, 2002 4:28:57 PM] [edited by - quantum_red on August 14, 2002 4:29:22 PM]

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ummm...i know how to do it, if the plane contains the origin...otherwise, you need one more bit of information (a point on plane or the D-value (which is basically some point on the plane dotproduct its normal)).

Let p be the point on the plane
let n be the normalized normal of the plane

Let p''=normalized p= p/|p|

let q=p*n

Let q''=normalize q.=q/|q|

your box should have following vertices
A: p-p''*8-q''*8
B: p-p''*8+q''*8
C: p+p''*8+q''*8
D: p+p''*8-q''*8

not that the square produced will be in an orientation dependant on where p is located.

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Could you dumb this down a little for me? I''m a C programmer :-)
I have these functions available to me, but I''m not sure how to work out your example.

VectorSubtract()
VectorCopy()
VectorScale() << multiply
VectorNegate() << invert
VectorNormalize()
Dotproduct()
Crossproduct()

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