Constraints

[SublimeOne]

Prof. Watkins (or anyone who knows),

I've read all the other conversations about constraints and still don't get it. What are locators?

[Professor Watkins]

Locators are empty objects. They don't render and they have no geometry of their own. They essentially are there to be well, locators - that is they help other objects locate their position, rotation etc....

Just like any other object in Maya, you create them in the (suprise, suprise), Create pull down menu. Just go Create>Locator.

This will create a green star-like object that you can move around. Rename it to L_Eye_Target (or something like that). Select the locator, shift-select the left eye and apply an aim constraint.

So now, you can move the locator and the eye will follow it; but when you render you won't see the locator object.

[SublimeOne]

cool, so the same applies for picking up an object? Place the locator in the palm(or child of palm joint) and place object in hand, create - aim constraint? Key object to where you want it to go?

[Professor Watkins]

Constraints are indeed used for picking up objects. It's a little trickier, but one thing to notice is that when you set up a constraint node, if you select it, you can see the object it is constraining to in the Channels Box.

This is important because you can set up multiple constraints. So an object can constrain to more than one locator, or a locator and a hand, etc....Then you can animate the influence that these constraints have over time.

So a ball can have a constraint to a hand joint and a locator. The locator is up in the air. Start by having the ball constrained to the hand; then aniamte the ball moving like it's throwing the ball, then when the hand releases the ball, you change the constraint weight to the locator, and viola! the ball leaves the hand and flies into the air. Reverse the process to have the hand catch the ball again on the way down.

[Professor Watkins]

Here's a quick sample of the idea in action.

[SublimeOne]

awesome, thanks