Re: [Algorithms] coordinate systems

[Casey M. <gd...@fu...>]

> All I asked for btw, was what is the most commonly used system in 3D
> application such as max, maya, or thirdparty engines such as renderware,
> netimmerse, qzr, and things like that...

MAX is right-handed
Maya is right-handed
SoftImage is right-handed
Lightwave is left-handed

I don't know about RenderWare or NetImmerse.  Personally, I always pick
right-handed, because the two primary game art tools (ie., MAX & Maya) use
it, the vast majority of math books use it, and neither OpenGL nor D3D
care which you use so long as you are loading your own matrices and not
using their matrix building routines (which I never do anyhow).

Plus, with right-handed, you CAN use OpenGL & D3D's libraries if you want,
because if I'm not mistaken, OpenGL is always right-handed and D3D can be
set to use right-handed in its newer releases (someone correct me on this
if that's not the case - I never use these routines).

> And if I understand correctly, using a right handed system, the 3 columns in
> a matrix point right (+X), up(+Y) en backward(+Z), and the cross-product of
> X cross Y, which is counterclockwise, should also point backward (+Z).
> backward in terms of "out of the screen".

Correct.

> How about quaternions, do they have a handedness? and if so, how can you
> determine that?

Just like a cross-product, it can be made any way you choose.  Normally,
quaternions are made so that they obey the handedness of the underlying
coordinate system.  But you could write them so they're opposite it (ie.,
so they rotate clockwise instead of counter-clockwise, etc.).  See my
previous post about quaternion handedness, where I do the i/j/k
derivation.

- Casey