Quaternions

[xerid]

using quaternions, does

TRANSLATE + ROTATE == ROTATE + TRANSLATE

also, are opengl's matrices a matrix form of
quaternions

[Mike F]

>using quaternions, does
>
> TRANSLATE + ROTATE == ROTATE + TRANSLATE
>

No. This is nothing to do with quaternions - it's a general property of rotations and translations. Also, there's no way to express a translation using a quaternion.

>also, are opengl's matrices a matrix form of
>quaternions

No. A quaternion describes an orientation/rotation, nothing more. A 4x4 matrix (as used by OpenGL) can describe such things as rotation, translation, shearing, perspective projection etc.

[xerid]

how can. or are, quaternions be used in computer graphics...the concept that is.

[This message has been edited by xerid (edited 03-02-2000).]

[Mike F]

They're usually used for skeletal animation, mainly because it's a lot easier to blend between two quaternions than it is using matrices.

[Nathan d'Obrenan]

Xerid: Quaternions are a good way of representing rotations, however they are hard to visualize (bad for finding a bug http://www.opengl.org/discussion_boards/ubb/biggrin.gif). Their is a TON of info on the net regarding quaternions, definately look into it more.

Oh also a really awsome site that I would like to plug is Ask Dr. Math (www.askdrmath.com). Very useful for almost every algorithm / problem you might come upon, and its solution is explained very well. Great questions/answers pertaining to quaternion numbers as well.

[xerid]

Originally posted by Nathan d'Obrenan:
Xerid: Quaternions are a good way of representing rotations, however they are hard to visualize (bad for finding a bug http://www.opengl.org/discussion_boards/ubb/biggrin.gif). Their is a TON of info on the net regarding quaternions, definately look into it more.

Oh also a really awsome site that I would like to plug is Ask Dr. Math (www.askdrmath.com). Very useful for almost every algorithm / problem you might come upon, and its solution is explained very well. Great questions/answers pertaining to quaternion numbers as well.

do you have a si,ple example of using quaternions (source code) verses OGL matrices.
also, it seemd that quaternions would be faster, and does that completely throw out OGL matrices.

[paolom]

Just to give an idea, Tomb Raider uses quaternions to smooth the rotations of the camera tracking Lara. The smooth effect is achieved by interpolations.

[mike j]

check this site http://www.darwin3d.com/gdm1998.htm

[Nathan d'Obrenan]

Xerid: Sorry, right now I don't. I have just been way to busy, but I do plan to have a kind of personal programming page up soon. I just thought of it now, but I think that it would be real cool if I posted little advanved math tutorials or something with little demo programs. The best advice I can offer re: quaternions is to read books, surf the web a bit and really just experiment on your own (Kind of like everything else in life http://www.opengl.org/discussion_boards/ubb/smile.gif Its only math!