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jeremyhardin
11-17-2005, 05:59 PM
what are they?

similiar to XSI and maya, where you've got a view rotation handle as well?
or XSI where you've got view, local, and global to choose from?

I dunno what they are.

RedBull
11-17-2005, 06:27 PM
Normal XYZ angles are known as Euler Angles, and quite often suffer from dreaded gimbal lock, when animating certain rotations (neck, shoulder etc)
Euler has problems when interpolating arbitrary orientations.

And this is when Quaternion works well, And uses a single unit of XYZ to interpolate the shortest path between two angles.
A better explanation, can be found via a google search..... I'm sure..

basically it chooses a smoother and more accurate way to work out the angle
of rotation, for certain problematic circumstances.

jeremyhardin
11-17-2005, 06:29 PM
thanks. i did the google stuff and dictionary.com, but i'm still having trouble with what that really means.

jeremyhardin
11-17-2005, 06:51 PM
**wonders if everyone is busy looking it up, due to lack of further response**

or perhaps it takes more than a few minutes to get another reply :)

RedBull
11-17-2005, 06:55 PM
Here is some techinical maths/algebra docos on it,

http://www.gamedev.net/reference/articles/article1199.asp
http://www.gamedev.net/reference/articles/article1095.asp
http://www.scs.leeds.ac.uk/mart/quaternions.html
http://www.stormingmedia.us/44/4451/A445163.html

And as about as English as i can make it:

"Euler angles can also suffer from gimbal lock, which is the phenomenon of two rotational axes aligning with each other so that they both point in the same direction. This happens because the XYZ axes are not independent, so changing one axis can affect the preceding ones. For example, if you apply a 90-degree rotation to the Y axis, it causes the X axis to coincide with the Z axis so that rotating in X and Z has the same effect. "

"Quaternion interpolation provides a way to overcome these limitations and provide smooth interpolation with any sequence of rotations. With this type of interpolation, the XYZ angles are treated as a unit to determine an objectís orientation so they are not restricted to a particular order of rotation axes. Quaternions interpolate the shortest path between two rotations"

jeremyhardin
11-17-2005, 07:02 PM
thanks again redbull. i see what your saying, but i suppose i'm phrasing my question poorly. my question is moreso...

Is the new feature of Quaternion Rotation a purely alogorithmic feature, or will there be some new way to interface with the selected object(s) rotation? (i.e. new types of handles, etc.)

RedBull
11-17-2005, 07:28 PM
I'm not sure on the LW9 implementation.

It could just be an Item Motion Plugin

LW9 mentions "a new rotation controller" so i'm not sure...

XSI and others offer Euler to Quaternions and vice versa tools
and also offers Quaternion Fcurves..

So maybe you will see a GE implentation of Quaternion curves and keys,
or maybe the new controller, will implement them for you...
Your guess is as good as mine. :)

But maybe in the next month, you will see some videos demonstrating them! ;)

jeremyhardin
11-17-2005, 07:30 PM
indeed!

:decaf

toonafish
11-18-2005, 02:24 AM
There already came a quaternion motion modifier plugin with IKBooster. Sometimes it helps in gimball situations, but not allways.
I wouldn't be surprised if they are talking about exactly this plugin.

Maxx
11-18-2005, 07:02 AM
I thought that 8.0 introduced quaternion rotation algorithms to reduce gimbal lock. Am I totally nuts here or does anybody else remember hearing about this? I thought that was why we had different coordinate options in Layout?

toonafish
11-18-2005, 01:34 PM
I thought that 8.0 introduced quaternion rotation algorithms to reduce gimbal lock. Am I totally nuts here or does anybody else remember hearing about this? I thought that was why we had different coordinate options in Layout?

Wish that were true, but as far as I know Euler is still the standard in LW. The World an Local coordsys that were introduced in 8.0 are quite an improvement, but in the end all rotations are still solved within the Parent Coordsys.

You can see it very clearly when you rotate a Null 90 degrees in the Pitch on frame 10 ( make sure you create keys for HBP manualy when you using 8.5 ), then switch to Local Coordsys and rotate it on the Local heading 180
degrees on frame 20. You'll see it whobble between frame 10 and 20 while you'd expect it to just rotate over the Local Heading.

Now add QuaternionBooster, and the whobble is gone :D

KevinL
11-18-2005, 03:01 PM
World, Local, Object coordinate modes? Just a thought.

Have a great day (if you so desire)

jeremyhardin
11-18-2005, 03:15 PM
quaternion booster??

oh, just found the motion modifier. so then what's this in 9?

News! We've kept the motion modifier!?

jeanphi
11-18-2005, 03:39 PM
Quaternion booster is not working with LW IK but only LW FK and IKBoost.
I hope it will work for all in LW 9.

harlan
11-19-2005, 01:44 AM
Hey Jeremy (and others if interested) - not related to Quaternion Rotations, but you mentioned dictionary.com ealier. Check out onelook.com for your dictionary needs. It's pretty cool.

oh, and quaternions are good. :)


harlan