Dir vector from two 3D points.

This is the basic of vectors...
with two point you can define two vectors.
If you know the first and second points (beginning and ending points) you can only have one vector.

(I wonder if I''ve well understood)

A(xa,ya,za)
B(xb,yb,zb)

Dir(xb-xa,yb-ya,zb-za)

IF everything defined in a 3d orthonormed system.

-* Sounds, music and story makes the difference between good and great games *-

Maybe I should describe what Im trying to do, to make sure we are on the same page =)

I''m using OpenGL, I want to place my camera at P1 and I want to use gluLookAt so that I can get camera to follow P2 as it moves around while keeping camera centered on it.

The 3 parameters I''m not sure about are dir.x dir.y dir.z

Rick

I think the equation is right IF you''re usign world coordinates for both objects.
IF the dir is defined in the Camera cooridnates then it''s a little bit harder.
But I don''t think it''s that, my first answer should be ok.

(I''ll check it this evening @ home)


-* Sounds, music and story makes the difference between good and great games *-

What you''re searching for is a LookAt() function.
One of the samples in the DX SDK contains a good function doing this, it orientates a camera (or any other matrix) to point onto a given vector. I know you''re using OpenGL, but since this is with full source and doesn''t use MS-specific things, it should be no problem to convert it
(I think OpenGL vectors should also contain x, y and z like the microsoft ones *g*)

\samples\multimedia\d3dim\src\d3dframe\d3dutil.cpp
search for ''lookat'' in the file.
If you do not have the DX SDK I can mail you the file

-Markus-

I have the 6.1 sdk but it''s only the libs/h files if you could e-mail that to md2ge@hotmail.com I''d be gratefull.

Problem is I don''t plan to use this only for camera movement, I''m working on a landscape 3d engine and I want to implement a line-of-sight function.

Thanks