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Started by digitec devil Mar 21, 2005 at 1:02 PM 3 replies 1.6k views

Original Post

Mar 21, 2005 at 1:02 PM

I've run into this problem a number of times and never really looked into it enough to get any answers. The problem is that I will rotate an object arbitrarily, then any subsequent translations, such as one to position the object in the world, are also affected by this rotation. So how do I translate to get the object in the desired position after this rotation has been applied? [Edited by - digitec devil on March 21, 2005 4:49:16 PM]

nts

115

nts

Mar 21, 2005 at 1:12 PM

Whats the difference between your object and world space?

Can't you translate first and then do the rotation.

Alternatively what about (if using OpenGL)

glRotate(...);glPushMatrix();glLoadIdentity();glTranslatef(...);glPopMatrix();

digitec devil

Author

digitec devil

Mar 21, 2005 at 1:48 PM

In this case I've got two rotations followed by a translation. The translation is supposed to put the object into world space, but my local coordinate system has been rotated arbitrarily, so translating has to take that into account, no?

Thunder_Hawk

Mar 21, 2005 at 2:21 PM

I'm not quite sure what you are trying to say, but I'll give it a try:

pseudo-code:
pushMatrix();
translate (x, y, z);
rotate();
rotateAgainAlongADifferentAxis();
translate (-x, -y, -z);
draw();
popMatrix();

That will rotate an object in place, even if it's not located at the origin.

[EDIT] Whoops, I got the translations backwards.

[Edited by - Thunder_Hawk on March 21, 2005 4:21:39 PM]

digitec devil

Author

digitec devil

Mar 21, 2005 at 3:44 PM

Got it sorted, I can have serious lapses in mental capacity in the mornings :/ thanks guys.

[Edited by - digitec devil on March 21, 2005 4:44:53 PM]

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