View Full Version : IK SetUp Problem

03-11-2008, 03:41 PM
I'm trying to animate a step ladder opening and closing and can't figure out how to animate the brace mechanism that locks/keeps the ladder open. Anyone have any ideas?


03-11-2008, 05:39 PM
If the ladder doesn't have to open/slide on the floor just open and close the ladder using FK. and set up a simple IK chain between the legs of the ladder and control the locks with this(have the two ends of the lock chain parented to the legs).
If you have to slide it on the floor then I would use 2 ik chains. One for the legs one for the locks, and have the two ends of the lock chain parented to the legs. LW's native IK isn't the best at the moment so I recommend using PLG ik. Here's a simple scene with PLG.

03-13-2008, 10:33 AM
PLG doesn't work on my MAC, so I'm trying to rig without...

03-13-2008, 11:12 AM
I don't think you need PLG, I believe you can do it easily with IK, since you only need IK rotation in one plane.

A tip would be you need to setup your hinge as 6 parts, each parented to one another. It's like a bone chain, but you don't have to use bones. You can apply IK to regular objects, and then you can modify your pivot locations using modeler.

The order of objects would be (starting with base, each parented to the prior):
Null Base
Hinge obj
hinge lock obj
hinge obj
Null Child

Then the final null would be the GOAL for the Null Child, but you wouldn't parent this null to anything except your ladder, or wherever you need it.

You could also then parent your Null Base to the other side of the ladder. WHen the ladder opens, it should move yourhinge accordingly.

03-13-2008, 03:27 PM
I forgot that you could apply IK to objects other than bones... so, I set up a chain, pointed it to a goal, constrained rotations, and voila!