[Opensim-users] NPCs: Quaternions and Vector3?

[Justin Clark-Casey]

On 17/11/10 23:11, bodzette Coignet wrote:
> So here's a question:
> If I want to make an NPC move I need to know which orientation an NPC has and what way I want it to go.
> So I can pretty much understand a Vector 3 which would be move in the direction of +/- for x,y,z where x is left-right?,
> y is back-forward? and z is up-down?
> But quaternions I'm having a hard time getting my head around and I have a hard time coding something when I don't
> understand what it is.
> Is it some representation of rotation in 3D similar to the vector but for rotation instead?
> Is it measured in the naively intuitive +/- 0-360 degrees for each of x,y, z or is it measured in something more
> esoteric like radians or something else entirely?
> Anyone give me a quaternions-for-dummies elevator speech run-down so I know what I'm working with?

Unfortunately I can't do that but I do suggest taking a look at the LSL quaternion/rotation conversion functions, such as

http://lslwiki.net/lslwiki/wakka.php?wakka=rotation

I'm finding that

http://www.amazon.co.uk/Quaternions-Rotation-Sequences-Applications-Aerospace/dp/0691102988/ref=sr_1_1?ie=UTF8&qid=1290040061&sr=8-1

is a good book for understanding these issues, if a little pricey (don't ask me any questions, I haven't got to the good 
bits yet!)

-- 
Justin Clark-Casey (justincc)
http://justincc.org
http://twitter.com/justincc