at method
Computes a position on the ray according to the given t value
and stores the result in the given 3D vector. The t value has a range of
0, double.infinity where 0 means the position is equal with the origin of the ray.
Implementation
Vector3 at(double t, Vector3 result ) {
// t has to be zero or positive
return result.copy( direction ).multiplyScalar( t ).add( origin );
}