Understanding the Transform3d

[Usul]

hi,

do you guys know good tutorials for understanding the matrix used by Transform3D?

I know how to move or rotate an object, but I dont know how to turn an object so that it looks at the direction of another object.  There I want to understand the math now.

thanx,

Usul

p.s.
and I DID google for hours, I swear.  But either the sites only talk about very basic stuff or they are very complicated.  I didnt find anything in between.

[Usul]

OK, I drawed the matrix on my HUD and now Im starting to understand.  Its obvious where the position is stored and I guess I can figur that rotation thing out by myself.

But what is the last colum of that Matrix4d used for?  Its always (0,0,0,1).


Still I would appreciate any good tutorials on that subject.

Edit:  The big question is:  How can I determine from that Matrix4d in which direction (in angles to the axis) I am facing?

Edit:  A maybe simpler answer would suffice:  How can I get the direction (represented as a quaternion or a matrix) between to points/vectors?

[Jeff]

See Transform3D.lookAt()

The matrix is  a standard 4x4 vector transform matrix.  Look at your favorite Vector Algebra book or any basic 3D graphics book (eg Foley and Van Damme)

Games published by our own members! Check 'em out!

[Usul]

See Transform3D.lookAt()

I tried it.  I wanted my modol to look at the origin (without changing its position) every time I press a button.  But it just jumps around (at least the up-vector seems to work).  Here's my code:

1   2   3   4   5   6   7   8   9

//GET CURRENT POSITION        tg.getTransform(transform3D);         Vector3d pos = new Vector3d();         transform3D.get(pos);         System.out.println(pos.x +" " + pos.y+" "+pos.z);         //LOOK AT THE ORIGIN        transform3D = new Transform3D();         transform3D.lookAt(new Point3d(pos.x,pos.y,pos.z),new Point3d(0,0,0), new Vector3d(0,1,0));         tg.setTransform(transform3D);

Edit: Oh wait, it DOES work.  I just forgot that I didnt place my cube3d in the origin (in other words: stupid mistake).  OK, thanx.