Bones losing their binding - and bad bone dynamics

SpaceBoy64 · Post by **SpaceBoy64** » Sat Oct 03, 2009 6:38 am

Is it my imagination, or are my bones losing their bindings?

On many occasions I have set up bones and gotten them to work right. Later I will open the same file and find that pieces of my character are moving around which shouldn't be. I know I had them working, but now, they're not working right. It's like it didn't save right or something has caused the bones to come unglued. It's very frustrating because I have to re-do work over and over again. One character I imported into another scene, and it's bones started behaving very strangely. I had to delete them and start over again.

Another thing that doesn't seem to work right is bone dynamics. I had set up some bones for some hair that I wanted to move around with the character. I tested it and it seemed satisfactory. Later, the bones became detached and did nothing. I got working again, and I began noticing that the movement was not always the same at a certain frame. I can move the timeline pointer to frame 50 and then back to frame 2 and back to 50, and the hair's movement would be different each time, and in the final render, this movement is never as pronounced as it is when scrubbing through the timeline.

I am using AS6P on a Windows machine.

heyvern · Post by **heyvern** » Sat Oct 03, 2009 7:14 am

Bone dynamics are "time" based. They work in relation to changes in time meaning the movement won't be the same if you skip around the time line. The movement should remain the same if you start at frame 0 and move forward. if you have skip frames turned on or start scrubbing at a different frame or scrub back and forth the movement will appear to "change". The dynamics are behaving differently because they are based on the position of the bones of each frame.

As for the other problem I can't say without seeing the problem file. If you can replicate the problem, save the file and post it for download before fixing it. After you "fixed" one of these problem files does the problem return? Is this a problem you have to fix over and over? Can it be repeated? Would love to see the file. I am sure it has a logical explanation.

-vern

SpaceBoy64 · Post by **SpaceBoy64** » Sat Oct 03, 2009 9:37 am

Shouldn't bone dynamics be based on the nearest keyframes? Why should it matter how fast I scrubbed through the timeline? That's irrelevant and deceptive for previewing. When I click on frame 50 and render it should always look the same.

Is there a way to calculate the bone dynamics and bake the motion?

The other problem is hard to replicate. I just can't trust that when I do something its going to stay done.

I had set up a character with bones, I set the eyes to be layer bound to the head bone. Then I set up this hair with bone dynamics and suddenly the eyes were moving around with the hair. When I re-set the layer binding for the eyes, they stayed put, until I did something else and the hair points lost their binding to the dynamic bones and I had to re-set everything.

I'll see if I can replicate it later.

Thanks.

heyvern · Post by **heyvern** » Sat Oct 03, 2009 4:50 pm

Bone dynamics can not be baked. However if you move along the time line in "sequence" to the frame you want to render that should give you consistent results. Turn frame skipping off and start at frame 0 and hit play. Stop it at the frame you want to check or render.

Dynamics are based on the "previous" frame. If you jump from frame 2 to frame 50 then the dynamics on frame 50 are based on frame 2 not frame 49. With skip frames on frames are skipped so the dynamics aren't accurate. If you work with dynamics in a 3D program that does calculate ALL the frames before the current frame you will know how much of a pain it is to calculate all the frames. It takes a lot of time and slows things down. Dynamics are for automated motion. You can't control it. It's for secondary motion to avoid key framing. Because of that it isn't always going to be "perfect" and you can't control it as well.

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I can't help you with the other problem without seeing the file. I have not encountered this myself. It could be a problem with dynamic constrained bones which I don't use very much. Looking at the file would help. I want to make sure that we eliminate user error before assuming it is a bug of some kind.

If it IS a bug a file demonstrating this will be needed for the developer to determine what to fix.

-vern

SpaceBoy64 · Post by **SpaceBoy64** » Sun Oct 04, 2009 10:14 pm

heyvern wrote: Dynamics are based on the "previous" frame. If you jump from frame 2 to frame 50 then the dynamics on frame 50 are based on frame 2 not frame 49.

I think it would be a simple fix to simply have this difference always based on the actual previous frame (49 in this case) rather than the last frame the timeline pointer was at. This would solve the confusion. If you're skipping frames, you don't want the animation to be more exaggerated because of that.

Here's another problem. I am setting up a new character and I have some eye shading that I want to be locked to the eye motion. I went to bind this layer to the head bone, but I can't because it's a switch layer? I could have sworn I did this on a previous character. Now it seems I can't. I figured out a way to make it work, but I swear I used layer binding on a switch layer before because I had eyes that remained stationary when I moved the head bone, then I fixed it by binding that layer. On this character I guess it's just using the default binding, but that's not always desirable. (okay, sorry, it's nested inside a folder, and I wasn't on frame zero. This sort of thing is making me think I'm losing my mind.)

Here's one I really think is not right. I want to set ease in and ease out for keyframes on switch layers, but there is no option for this. Why?

I have reverted to using switch layers instead of actions because I also want to use bones, and using actions seems to negate the effect of bones.
Is this true?