constraints are jerking

Hey Guys

I have an issue with some constraints were they are jerking around even when they are not moving. I doors have been linked as to save memory. If any one has any ideas, that would be great


We need to know little more detail on your door build to guess whats wrong. How was door action done? Are you driving it?

The Empties that I had the doors attached to were the incorrect scale. I applied the Scale and all is fixed.

Edit : Nope, lied

It’s difficult to troubleshoot without access to a blend file with the problem.

The video may show a common symptom however. Twitching or crazy moving objects or bones is often a cyclic dependency issue (a loop somewhere) in the parenting, constraints, and modifiers. The System Console will usually indicate errors like this. System console can be toggled on via the main menu > Window > Toggle System Console. If it does give that error it will tell you where the loop is.

This a shot in the dark. Other issues may show similar symptoms.


Sometimes constraints aren’t always the best way to do this thing, even though they may be easier to setup because of how the menus are arranged. They seem to cost a bit of overhead and aren’t always as predictable as they should be.

An alternate way to do this may be to use drivers, add a custom property to the model, and a fairly minimal scripted expression in the driver. A bit more of a pain to setup at first for those of us less technically inclined, but more bare-bones under the surface and not running code that does a couple other things besides just the one thing you need it to do.

In your case, it might be a custom property of “door open” with a value range of 0.00 to 1.00. And you’d have drivers controlling rotation on the hinge axis of the empties the doors are attached to. The script would just involve multiplying the custom property value by the amount of rotation (in radians) needed to fully open the door. Animating the door opening and closing would just involve keyframing the “door open” custom property value.