Cineversity

Hi:

I’m trying to rig a set of folding doors using IK, but I’m not having any success making them bend the way I want.

The attached scene uses an IK setup on the right and a setup that uses an Aim constraint on the left.

In my attached scene, when the End Goal on the right moves to the left the doors fold back in the +Z direction.  They’re supposed to fold towards us, in the -Z direction, as is happening in the setup with the Aim constraint.

I think this is happening due to the way the pivots are set up; the middle pivot is farther back than the axis of the Pivot Panel and END, so the chain wants to bend in the +Z direction.  This arrangement emulates how the real doors are built.  The middle hinge is on the back and the pivot panel and end of the handle panel run along a track that’s a few inches forward of that middle back hinge.

I’m not super-versed in IK, so I’m hoping there’s a simple solution I’m missing.

As seen on the left I can get so-so results by animating the rotation of the Pivot panel and using an Aim constraint on the Handle panel to fake it being in its track, but it’s not very smooth.  The target of the Aim constraint has to move in a weird way to make the end of the Handle panel look like it’s in its track.

Any suggestions?

Thank you.

Shawn Marshall
Marshall Arts Motion Graphics

Hi Shawn,

Yes, the IK is more interested in a straight line and then go, instead of bend in one way and then jump over that dead-point.

I have set it up with joints and placed the door-panels so the door connections are placed correctly and can be easily adjusted. This could be done with the axis tool, but it is so much faster, and I would think more precise. As a side effect, exchanging the panels is without penalty.

Scene file
https://www.amazon.com/clouddrive/share/mgRFJUOaEhfIWkMuLMlP5E3Q4T7IcCCyg0bQoL4NCQr
Move the time slider to see the doors working. I have set the coordinates in freeze mode, so a simple zero out (P) brings the original Goal position back.

There is certainly an Xpresso set up thinkable instead.

Cheers

Hi:

Once again, thanks so much for the quick reply and sample scene.  This should work well for my scene.

Best.

Shawn

You’re very welcome Shawn.

Please let me know if there is anything else. I’m happy to have a look at it.

Cheers