[Papervision3D] Rotating around world axis

[Tim Knip]

Hello,

All rotations are already done using quaternions.
So gimbal-lock should *not* be appearing, and afaik it doesn't.
Your sample-swf behaves absolutely normal.

There is no such thing as 'axis becoming parallel' or 'losing an axis'
as you state.
Again: everything behaves as it should:
z
|
*----x
rotateY 90 results in:
     y
     |
x---*
a further rotateZ 90 results in:
y__*
     |
     x
Now for your problem... see above graph...
Where it boils down to: you need to understand that after one
rotation, any following rotation might not be what you expect...

Tim


2007/11/13, pokypin <dustin at curiousmedia.com>:
>
> I have done some more research and discovered a name for the problem I keep
> running into. The problem is apparently known as gimbal lock, and is also
> apparently an inherent flaw in using Eular angle calculations. From what I
> have found, gimbal lock is unavoidable using Eular angle calculations. By my
> understanding gimbal lock occurs when two axis become parallel, resulting in
> the equivalent of losing 1 axis. Also by my understanding this occurs
> because in the Eular system, rotations are calculated on the XYZ axis in
> order, not simultaneously. The most basic step to solving this problem seems
> to be using Quaternion angle calculations instead. From what I understand
> Quaternion rotation calculations are all made simultaneously, thus avoiding
> gimbal lock.
>
> I was able to find a few threads where the issue was discussed by what
> seemed to be members of the PV3d team. From what I found, it seems,
> Eular/Matrix3D calculations were chosen because they were less complicated,
> and also less CPU intensive.
>
> Anyways, that was probably a very crude and bad explanation, but I think I
> basically understand the problem. Am I right to assume that if papervision
> was modified to use Quaternion angle calculation instead, then gimbal lock
> would not occur? While I think I understand, I definitely do not have the
> knowledge necessary to make such a modification.
>
> So I suppose I could restate my question to: Does anyone know how to easily
> modify papervision to avoid gimbal lock, by using Quaternion or any other
> method? I don't know how many aspects would be involved to truly port
> everything over to Quaternion, but all I am really interested in is doing 90
> degree rotations on any axis without running into gimbal lock. Using too
> much cpu doesn't scare me away at this point, I just want to see it work. I
> feel like I may be rambling now, but I just wanna do "SIMPLE" rotations! :P
>
> Ok, so for everyone to see it in action I have created a sample:
> http://www.dustinbahr.com/pv/gimbalLock.html
>
> Pressing x, y, or z, will do a 90 degree rotation on the appropriate axis.
> red = x, green = y, blue = z. To see gimbal lock occur is very simple. Press
> y to rotate around the y axis, then try pressing either z or x. You will see
> that they both rotate around the "x" axis. (note: if you press z first you
> will see that it actually is trying to rotate around the z (blue) axis.)
> --
> View this message in context: http://www.nabble.com/Rotating-around-world-axis-tf4486910.html#a13731436
> Sent from the Papervision3D mailing list archive at Nabble.com.
>
>
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