Slop in the connectors
I've been working on a character and I noticed something looked a bit off about the hands when running, though hard to tell as they're moving fast. So I attached a camera to the hand to see what was going on.
I should note I gave this character jointed fingers. By default, the joints are springy so they have a bit of play when walking, which works great. For the run keyframe, however, the fingers are keyframed stretched out, and tightness and springiness are set to 100%.
When I attached the camera to the hand, I discovered the finger segments are actually being pulled out of their sockets as if the joints were made out of elastic rubber.
So my question is, is there a trick to getting connectors to behave like they are made out of steel, and not rubber bands?
Here's a video: https://youtu.be/-OoJJY8MuGo
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I've found that sometimes once I've made a connector springy, it won't want to go back to being rigid. Ever. I think it has something to do with the fact that joints start out at 0% and rigid, but they're supposed to be more rigid as the slider goes up.
If there is a trick to fixing it, I would love to hear it. I've always run out of patience and replaced them with new connectors before I could find a solution.
Is it possible that one of the keyframes is set to being springy? -
Hah! When I discovered the issue, I had a look at how you did your characters as I recalled you rigged the fingers. I was perplexed as to how you had 0% strength and springiness with no issue. Now I know why.
I took a look through the keyframes and everything looks good there. Then I tried setting the tightness and springiness to 0% then 100% on the keyframe. I even tried keyframing the angle limit to 0. Nada.
I guess I'll just have to replace the connectors and not touch those sliders. Kinda seems like a bug. :/
On the bright side, keyframes have a springiness setting, so that might work out ok. -
Yes, I would recommend using springiness on the keyframe itself. And if the pose is keyframed, you don't need the connectors to have different settings or anything; the keyframe will do all that work for you.
Something to be aware of is that "strength" is actually how hard it is to *move* the connector's position. As in, how hard it is to rotate that connector using physics forces (including pulling with the imp). So when at 0%, it's very easy to move it using physics forces. At 100%, physics forces won't affect the position (theoretically). But it does *not* mean it cannot be moved at all. And it does not mean it will stick to the original pose; it will be stuck at whatever position it was when it became "strong" until physics forces are strong enough to push it into a new position.
Springiness on the other hand is the connector's ability to pull the position back to the original position. So when at 0%, it will just let the position be whatever it happens to be. At 100%, it will be forced into the original position. Somewhere in between puts some effort into getting it to the original position but it might kinda wobble a bit.
Maybe this helps you understand the issue? -
I still say the connector "springiness" settings are completely nonsensical. I understand it's one of those changes that would affect massive amounts of creations, but the current implementation is extremely frustrating.
Keyframes behave in the expected way, that the more you slide up springiness, the more wobbly the connections get. -
Even more to that point, I tried the tightness and springiness (and the rest of the options) in every combination of amounts, and it had no effect on the sloppiness. It seems connector physics and keyframes just don't play well together.
In the end, I just rebuilt the connectors as Andy suggested and didn't touch the tightness/springiness sliders. I set the finger parts to non-moveable, then created a keyframe with the fingers in the default pose to use as a spring control. They still disjoint under the strain a bit, especially the ball joints at the first knuckle, but I can live with it.
I do wish they'd tighten up the hard coded physics limits a bit, though. -
I recently made an octopus that has a literal butt-tonne of connectors in all the arms, and the joint separation was making me a little nutty as well. I even turned off collision on all the segments, thinking that might be forcing them apart as they touch each other. But, no luck. I suppose I could try turning the friction and gravity off on all of them as well... :-/
But like you, after a while I decided I could live with it. lol -
I think I've seen this issue in a jointed hand.
I ran through a lot of testing with the joints and sculptures and ended up fixing it using default bolt joints (ball joint on the thumb) and I reduced the density on every sculpt in the hand to minimum and made each one non-collidable.
I haven't seen the issue since. -
I did notice that bolts are far more stable than ball joints. I'm considering replacing the first knuckles with them, but I do like the additional degree of movement.
For what use, really? Who knows. I'm just stubborn, I guess. :D -
"I've found that sometimes once I've made a connector springy, it won't want to go back to being rigid. Ever."
Oh, man! This definitely makes sense. All my puppet animations end up requiring replacement connectors at one point or another.
As a positive, though, I've found that Strings at max tension are rock-solid. Dreams will rend its own physics engine asunder to maintain String length.
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