quaternions...sick of them.

dear /Sado & Maso/,

whats up with all those 3Dimensional Engines using quaternions? Why dont they just use a simple normalised 3DVector to descripe the Orientation of Objects instead of quaternions?

Anyone got a link to an easy understandable explanation for orientation quaternions?

gtfo

Why the fuck did my sage age this thread?

>>2
no, u.

simple normalised 3DVector
Are you talking about an axis-angle representation?
I can't find the link anymore, but I had a page that listed the pros/cons of each orientation system (euler angles, axis-angle, quaternions, and something else).  Quaternions are used to avoid gimbal lock, and when the user clicks and drags, the orientation movement is a lot more logical.

>>1

Gimbal lock.

why do you need 3 gimbals anyway? it looks like 2 is enough; there are only 2 angles in a spherical coordinate system. but i know shit about graphics programming so whatever.

>>7
You are forgetting about the roll angle.

SO(3)

>>8
it is possible with 2 angles though i think. say to yaw 90deg to the right, roll 90deg to the right, pitch 90deg up, the roll 90deg left.

>>10 *then roll 90deg left.

>>10
No idea what you are going on about, you just described rotation around 3 axes in relation to the object.  If you only use two angles to describe the current orientation of the axis that runs down the length of the object, then you have no idea if the object is upside down or not.

>>3
lowercase genius

>>10
Yes, you can use two angles to actually perform the rotation, but then how do you describe its current state? You need your rotations to be commutative in order to describe the orientation of the object, and for that you need a world-aligned orientation system which requires three angles.

As for using three angles, remember that your rotation axis are world aligned. It's not like flying a plane; if you 'pitch' +90, then the 'yaw' angle is now rolling the plane. This is why aeronautical terms are not used to describe the three angles, because they're meant for object-aligned rotations. But the real problem with three angles is that you can get your gimbals locked. If you 'pitch' +90, then 'yaw' no longer makes sense; this is why a lot of first person shooters won't let you look directly up, because without quaternions it would lock your rotation.

I described that poorly, so have Wikipedia or Google explain it to you:
http://en.wikipedia.org/wiki/Gimbal_lock