#Copy Tracks ?
4 messages in this thread
Yann,
Perhaps you can answer my question:
After having "copied tracks" from one object to another using the
"absolute" mode, I find that the two objects do not move and rotate the
same. I have checked the XYZ values in the Track Info boxes and they are
identical for both objects at each keyframe; yet the two objects are
actually offset from each other in position and counter to each other in
rotation.
Are the XYZ values relative or absolute? I thought those values
represented absolute positions and rotations.
Could the fact that the two objects have different axis cause the problem?
Thanks,
Alec Jason
Hi Alec,
I'm sorry that I missed your earlier question about this. Without seeing
your file, it's impossible to say what's going on. This is because
quaternions _are_ relative. Plus, object positions are subordinate to the
hierarchy.
If you've got a simple example of what you're talking about, zip it up and
email it over to me to take a look at and I'll let you know what's up with
it.
– G
Gary,
Thanks for the reply.
Could you please provide a definition for "quaternions." (Not found in my
dictionary or the 3DS docs index.)
I assume that quaternions are the XYZ values. Your message said that they
are relative — but to what, the object's axis?
(BTW, so the "G-" stands for "God" <g>)
Alec Jason
hmmm…. Quaternions are incredibly complex equations that provide answers
to rotational problems that occur when rotational axes pass through the
"north and south poles" of the world coordinate system. They were
developed in the early 1800's to deal with gimble lock problems on large
sailing vessels, and then Ken Shoemake rediscovered them about 15 years ago
(at Xerox Parc I believe) and wrote some great papers about how to use them
with 3D animation to provide smooth rotations in all cases. The books that
Dan Silva used to develop our routines are about 700 pages long (each,
there are two of them), and every page is filled with bizarre
mult-dimensional geometry equations. If you want specific references to
the book titles, or the ACM Siggraph papers that Shoemake wrote, I can dig
them up for you.
The rotations are all relative to the objects inherent transformation
matrix. This is the orientation that the object is in when you look at it
in Object Pivot mode. (again, if you want me to look at that file of
yours, zip up a simple case and send it on over and I'll explain what's
going on for you)
– G(lad to help)