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Eric
09-06-2000, 12:56 AM
I haven't posted a silly question for a long time so here it is !

I dunno if some of you use 3DSMax but there is something interesting in their rotation system : select an object, right-click on the "rotation button" and you can see a window with :

Absolute:World Offset:World
X : X:
Y : Y:
Z : Z:

I have had no problem copying this idea with the same dialog box etc etc...

My question is : How the hell do they find the coordinates of the rotation in Absolute:World after you have done several ones in Offset:World ?????

For example, if you use the following rotations with Offset:World :

X:5 , Y:7 , X:4

You obtain as a result in Absolute:World :
X:9.03 , Y:6.983 , Z:0.491

I know how to reproduce the effect of what happens when you use the Offset:World. Basically I load a rotation matrix that corresponds to the Offset and multiply the transformation matrix of the object with this new matrix.

But then, from this transformation matrix I have for each object, HOW DO I FIND THOSE COORDINATES IN ABSOLUTE:WORLD ??????

To be honest, I am sure I saw a method for that when I was studying maths but I can not remember the method, neither find my notes about it....

Please help !

Best regards.

Eric

P.S. : to those who think this has nothing to do with OpenGL, I just say : "You're right !".

Eric
09-07-2000, 10:44 PM
Well, I know it's stupid to answer its own question : this is just so that the topic comes to the top of the list again ; there has been so many new topics in the last couple of days that nobody tried to answer this one...

So, any idea someone ?!?!??

Eric

wolfman8k
09-08-2000, 05:22 AM
I think 3d studio max uses quaternions, not matrices.

Rob
09-08-2000, 09:13 PM
I'm not familiar with 3DSMax, so I might not even be answering the right question...
If by Absolute:World you mean relative to screen space, you can use gluUnproject to unproject unit vectors in screen space and find the corresponding axis in model space.
Like I said, I'm not at all sure that's what you're asking.