View Full Version : Is there a way to make a joint always face Z Down?

07 July 2010, 08:50 PM
Is there a way anybody can thing of to do something like a constraint to have a joint always aim down, but without aiming at anything in particular?

I have a joint on a motion path for some ooze drips, that the motion path deforms. I'd like the drips to always aim down regardless of where the drip is on the path, or how the path is rotated, etc. The drip is just on a single joint.

I tried something where a locator was placed just below the joint and the locator was point constrained to the group following the motion path, then the joint was aimed at the locator, but when the rig rotated and translated, the locators weren't lining up properly, and some weren't following properly, which I think was from an unforeseen dependency loop.

The only other things I can really think of are IK handles, add an extra joint, but then I still don't know how to get it to aim down, as the rig twists and rotates and moves, and I could use a hair curve, but that really seems like over kill for what I want to do.

The best thing would be would just have something that always has it point straight down in z, or -z for the other side of the rig, but I'm unfamiliar with any kind of constraint or expression like that.

07 July 2010, 09:15 PM
what you might do is a variation of what you were doing.

Attach a locator to the motion path.
Then point/parent (translate) constrain a joint to the Locator.

another thought is that you could write an expression that checked to see the direction of the joint and forced it to set downward.

a third option is to use nodes to set the joints rotation to always face the bottom camera.

07 July 2010, 09:37 PM
I may be missing something, but why don't you just turn off follow on the motion path? and turn off Inherits Transform for the joint?

07 July 2010, 09:53 PM
oh thats just too simple of a solution =)

07 July 2010, 10:30 PM
Ah. Thanks. I think I tried that before, but it wasn't working because I was getting double transformations from some hierarchy stuff before and didn't think to try it again (Rotated the whole rig, and the joints were flying off the rig). Turning of the follow got it working like I wanted.

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07 July 2010, 10:30 PM
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