a unit vector is simply a vector with a length of one...
ie... sqrt( (delta x)^2 + (delta y)^2 + (delta z)^2 ) = 1

look for a good tutorial on the net about vectors... flipcode.com has an entire series devoted to this type of stuff...

Edited by - lucid on July 7, 2001 9:02:14 AM

If you have two vectors, say u and v, that are not parallel, then they can determine a plane. For example, think of u=(1,0,0) and v=(0,1,0). Linear combinations of these 2 vectors generate the XY plane. The cross product of these 2 vectors is a vector that is perpendicular to the plane. You can determine its direction using the right hand rule.

Using i,j,k notation (where i=(1,0,0),j=(0,1,0) and k=(0,0,1)) the exact formula is:

if u=ai+bj+ck and v=di+ej+fk then

u x v = determinant( i j k
a b c
d e f)

= (bf-ce)i-(af-cd)j+(ae-bd)k