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As previously mentioned in the Ted Ty Talk Back post, due to limited time we were unable to ask Ted all the listener questions.  However, we will handle some of the extra questions in separate posts; here is the first.
Thanks again to everyone who sent in questions :)

Q & A: Parenting

Olov asks:

I always get intimidated by scenes involving props so i though i could take this
opportunity to clear some things up. do I constrain hand to prop or the other way
around? how do I get nice arcs, should i think about the arc of the prop or on the
hand, or both? I am also having real problem posing the hand so that it looks good
on the prop.

Great question Olov.  Props can be tough.  When constraining props it always depend on what you are planning on doing with it, but there are some general guide lines that are a good place to start.  For small, light props in most cases you will constrain to the hand.  For long, or heavy props in most cases you would constrain to the prop.  This all depends on how you will be animating the prop and what will be the lead and follow.  If your hand is driving the action, constrain to the hand, if the prop is driving the action constrain to the prop.
If you are having trouble plotting arcs I’d recommend installing an arc tracking plug-in in your software.  If you can’t find one, just get a dry erase marker and draw on the screen, but be careful, not all screens are good for dry erase(some lcd monitors).  If you cant draw on your screen you can always get some clear acetate and tape that over your monitor.
Yes, you should think about the arc of the prop, especially if its a sword or something that will be traveling across the screen a lot.
For posing the hand, do your reference.  The best is if you can hold the prop yourself, if not, find images on line and really study what the hand is doing.  The hand shape always supports the prop.
-Steve


I agree with Steve in most respects.  For light-weight small objects (cups, pens, toys) you should really always parent the prop to the hand, and for larger, heavier objects (boulder, refrigerator, car tire) I would parent the hands to the prop.  I’m pretty sure this is the same idea Steve is suggesting, but my way of thinking about it is different:
Rather than what is driving what, I think about what weighs more.
If your character is picking up a really heavy object you want to make the object feel really heavy.  In order to feel heavy the object needs to take a long time to start moving or change directions, which can be difficult to accomplish convincingly if it is parented to the hands.  The slightest rotation on the wrist will send the other end of the object a good distance across the screen space.
So if the character is picking up a boulder, his arms and hands are physically ‘driving’ the action, yet I would do it the other way around to be able to have full control over the placement/rotation/timing/spacing of the boulder that I feel I cannot have as simply if it is the child of another object.  Obviously, you run the risk of making it feel like the boulder is floating and the hands are just attached to it (well, they are…) so that’s where your understanding of weight and force will come into play by ‘faking it’ and making it look like the hands are picking up the boulder and not the other way around.
If you were animating traditionally then nothing would be parented to anything, you just have posing and timing and spacing at your disposal to make it feel convincing.  When in the computer, do whatever is technically easiest to achieve that.  The more time you spend fighting your setup, the less time you spend animating.
-Jacob