Nobody?

Well I searched a little more in order to solve my doubt, but so far I haven´t got any answer, but I did a little progress...

Now my problem is on the vector parametrization. I have a vector representing the gaze direction of a user, and I want to parametrize it!

The vector is similar to this [ 1 2 3]. How can I put it in this form:

r(t)=[rx0 ry0 rz0]+t[rxd ryd rzd] , where [rx0 ry0 rz0] is the origin and [rxd ryd rzd] is a point of the vector...

Hope you can help me... I really need this to continue my work...

cheers

Eduardo