The POV-Ray Cyclopedia

Bill DeWitt (bdewitt@gateway.net) asked for more information about vrotate and other vector expressions.

play ground Step 1
Creating the scene
Okay, this one is short and sweet:
#declare p1 = <-2,-1,-2>;
#declare p2 = <1,2,2>;

cylinder { p1,p2 0.1 texture { Cyan_Plastic } }

//sphere { 0, 1 pigment { rgbf 0.75 } finish { phong 0.5 } }

#declare p3 = vnormalize(p2-p1);
#declare p4 = vnormalize(p1-p2);

cylinder { 0, p3 0.1 texture { Yellow_Plastic } }
cylinder { 0, p4 0.1 texture { Purple_Plastic } }
The cyan cylinder joins p1 and p2. The yellow and purple cylinders are parallel to the cyan cylinder, and they both have a unit length of one.
pitfall Step 2
Avoiding pitfalls
There is one pitfall: 
#declare p3 = vnormalize(p2);
#declare p4 = vnormalize(p1);

cylinder { 0, p3 0.1 texture { Yellow_Plastic } }
cylinder { 0, p4 0.1 texture { Purple_Plastic } }
Here the yellow and purple cylinders point to the ends ot the cylinder, and they are not parallel, but they maintain the length of 1.
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