Weird Constraint Issue

[ArgleBargle]

Thanks to a trick I learned in these forums some time ago, I'm implementing some motion with a chain of bones, of which the end bone has a kinematic constraint to a null, and the null has a translate-constraint to another object. (Imagine, for example, an octopus leg hanging on to an object moving in a perfect circle. This method realistically is the only way to do it.)

 

Anyway, so far I've not had any problems with this until today.

 

I have a null that successfully translate-constrains to several objects. Then I constrained the null to a bone of an object (not the model bone). I tested the motion and it looked good. Then I positioned to a frame prior to enforcing the constraint and played the video and the null didn't move with the bone it was constrained to. Whisky Tango Foxtrot?

 

As I stepped through the frames, I noticed in the properties window that the enforcement was set to 0%. I could manually set it to 100%, but it immediately returned to 0% on playback. I watched the timeline in graph mode and I could see that the enforcement graph showed 100%, but the properties showed 0%. The more I think about what I'm seeing, the more sure I am that it's a bug.

 

Meanwhile, I have another object identically translate-constrained to the same bone and it continues to move with the bone properly. After I post this, I shall attempt to constrain my null to that object as a workaround.

 

Anyone have any ideas or advice for me on this one?

 

Note: I'm sure someone is going to ask how I got painted into this corner. Here are some further details: I have an animated, talking computer. Her mouse is at the end of a chain of bones. She's using the mouse to move around several objects, then she's opening a drawer and pulling out an object from inside it. I attach the null to the objects moved around, then apply a kinematic constraint of the end of the bone chain to the null. Finally, I attach the null to the drawer (which is a sub-part of a larger object) and I constrain a small object to the drawer so it appears as the drawer opens. The object and the null should move in lock-step with the drawer, and in turn, the mouse constrains to the null. However, the null is failing to move properly after the initial test. I.e., I get a one-shot behaviour, not repeatable behaviour.

[C-grid]

I am not saying it is but check:

enforcement time-based not constant

interpolation-method (choose a no sawtooth-figure)

[Luuk Steitner]

I've had a problem something like that with materials. After I had placed my objects in a chor I did some changes on the materials. I could render it one time ok, each second time one of my materials turned black. I tried keyframing it and all checked all possibilities but nothing helped. I decided to delete the objects from my chor and placed them again. This time no problem at all.

What I'm trying to say is that maybe if you made some changes in your constraints after they were placed in the chor a bug might have sneaked in. So maybe if you delete it from the chor and place it again it works, or you can try it out in a second chor. I hope this helps.

[ArgleBargle]

I never did quite get things fixed with the one null. It turns out that if I create a second null everything works just fine. I didn't do anything at all different with the 2nd null than with the first. I'll probably have to make a streamlined project and see if I can reproduce the bug and report it.

 

For what it's worth, there were already 4 constraints in the choreography for the null. I'm not sure how that influences things.