#Multiple "Parent" Links?
11 messages in this thread
Has anyone come up with any tricks to link one "child" object to two
independant "parent" objects? I realize that 3DS can only link a child
object in the keyframer to one parent object. But how do you handle
situations like, an animated person swinging something with both hands. If
you start linking the body joints from the pelvis up through to the arms,
lower arms, to the hands it works fine if the person is swinging the arms
independantly of each other. But if he is holding an object with both
hands, it can be _VERY_ difficult to animate the second hand to match the
movement of the first hand since you can't link them together without
loosing the existing links to the body. Creating a "dummy" (third) arm and
linking the left and right arms to it can still create gaps between the
joints (due to the pivot points). Anyone have any ideas? Thanks in advance.
My characters just can't seem to get a grip
on this situation…
-MM
Mike, there is no way to animate the hierarchy or otherwise manipulate the
links over time.
However… we simulate this effect frequently by splitting the final
animation up into different shots, in which each shot uses its own
hierarchy. You just put them together in Video Post and voila! There's an
amazing walking robot we're working on now that uses that technique…
you'll see it on the Siggraph tape.
If you'd like more info about the technique, let me know.
– G
I'm not sure if you understood my question correctly. My problem is a
person with both arms linked to a sword, and both arms linked to the body.
If I link the sword to the right hand/forearm/upperarm/body that works
great for one handed swings. But for two handed swings, I can't link the
left arm to the sword or vise versa because the left arm has to stay linked
to the body. This leaves me with the difficult (but not impossible) task of
animating the right arm to follow the left through very complex hierchical
based rotations of swinging the sword. As you can imagine the TCB compounds
the problem since the movement has to be very fluid. Clear as mud?
-MM
Mike,
How about this:
At the frame before the arms need to move in a linked fashion, scale down
the left arm to one percent and then scale up a copy of the arm which has
been linked to the sword (or other arm.
Then, after the swordfight, you can reverse the scaling of the real arm and
the copy and you're back to normal hierarchal operation.
Alec Jason
I guess I don't understand. The "scaled copy" of the arm would still need
to be linked to the sword as well as the body. How does this help me?
-MM
Mike,
I forgot to mention:
When you make a copy of the arm, use tracks/copy/relative thereby
duplicating the relative movements of the sword arm "into" the opposite
arm.
I'm not sure it will work but its what I would try.
It's an interesting problem.
Alec Jason
Interesting idea, but since the arms are separated at the shoulders and
joined at the hands, the whole movement of each arm is at different angles.
For instance, take swinging a baseball bat, the right arm is cocked and the
left arm is extended during the back swing.
-MM
Mike,
Yeah, I see what you mean about the two arms not always moving in the same
manner . . . hmmm . . .
I'm getting mentally fuzzy about the problem so this may be dumb but how
about scaling the arm down and then scaling a new one up as I first
suggested and then creating a new hierarchy (just for the new arm) in which
the hand was the parent to the lower arm and the lower arm the parent to
the upper arm. Then link the new arm's hand to the other hand.
At this point you could copy tracks/relative from the master hand to the
new hand. Then see what happens. You'll have to go through and fix each
frame and by moving the upper-arm so that it appears to connect to the
shoulder.
I do this kind of down and dirty, baling wire, and duct tape stuff pretty
often and there is usually a way to make it work.
Or you could get rid of that two handed sword and give the guy a nice
one-handed Glock 19, 9mm pistol.
Alec Jason
Believe me… I'm VERY tempted to go with the one-handed thing!
Thanks for the ideas. I've got to re-read those comments about scaling
though, I'll let you know how it works.
-Mike DT (duct tape) Morrison
I've got a better idea of what you're doing now — hmm… Alec's
suggestion is pretty interesting, and besides that, you'll just have to
keyframe the other arm manually.
– G
Yep, that's what I figured and so did. Not much fun though… it seems like
the best suggestion is to keep the number of keyframes down to a minimum,
and tuning down the TCB to remove as much arcing as possible.
-MM