Dynamic bone weirdness

[fae_alba]

I've been trying to get a dynamic bone chain to bring life to a shirt worn by Pappa Bear rather than using sim cloth. I added two dynamic bone chains to the shirt opening, then enabled collision detection. The issue comes about when stressing the range of motion as shown with the attached movie clip. I've fiddled with just about all of the settings with no real change in the behavior. I'd really like to get this to a point where I can animate the character without having to worry about the behavior of the shirt, but at this point I don't know if that is realistic.

 

shirt_testc.mov

 

One thing I'm wondering is if I need another bone chain to run along the bottom hem of the shirt to prevent the shirt from occurring. Anybody have ideas let's hear them.

 

[thefreshestever]

i can´t really see it in the screenshot, but you´ll want to make sure no bone of the chain collides with the mesh of his body. if there´s already happening collision at keyframe zero, kinematic chains tend to go haywire.

[fae_alba]

i can´t really see it in the screenshot, but you´ll want to make sure no bone of the chain collides with the mesh of his body. if there´s already happening collision at keyframe zero, kinematic chains tend to go haywire.

 

I had thought that too, so I added a pose to increase the size of the shirt (scale it up to try and make sure that that wouldn't happen. Sadly it didn't do any better. I'm going to try and re-work the bone chain and cp assignment so that the bones influence cp's running the height of the shirt and not the length. perhaps that will help.

[John Bigboote]

Hate to say it Paul, but I think you are messing with a feature of A:M that does not really work. I was just playing with CD(collision-detection) on a bone chain before I opened the forum and read your thread... it did not go well- AM crashed when I advanced frames. I can never figure out if the bone is supposed to react to another bone, or if the mesh attached to the bone with CD is supposed to react to other mesh's... If you really-really need a cloth effect on that shirt, I would resort back to SimCloth.

[fae_alba]

Hate to say it Paul, but I think you are messing with a feature of A:M that does not really work. I was just playing with CD(collision-detection) on a bone chain before I opened the forum and read your thread... it did not go well- AM crashed when I advanced frames. I can never figure out if the bone is supposed to react to another bone, or if the mesh attached to the bone with CD is supposed to react to other mesh's... If you really-really need a cloth effect on that shirt, I would resort back to SimCloth.

 

John, I'm going to perform one more test tonight, but I have a sneaking suspicion that you are correct. What it comes down to is how "realistic" do I want my shorts to feel. I'm on the fence about that, and I will most likely open up another thread for an open debate.

[markw]

Hi Paul,

Dynamics could still be an alternative to cloth but as you found its not without its own settings to endlessly fiddle with! And it will never be 100% automated, you will still have to go in and tweak things at key points.

As for DC collision detection, I too gave up with it. The results were usually quite wild!

Anyway, I've attached a very simple shirt setup here which may be of interest.

This uses an idea that Nancy told me, that of using a "Master" control bone at the base of a chain of bones that are using Dynamic Constraints so that you can have better control over their behavior.

Before using the Control bone, you will first need to "Bake" the Dynamics in the Choreography.

Next play through it and note where there's any pass through of geometry.

Key the Master Control bone (without actually moving it) just before and just after geometry pass-through. Now at a suitable point between these two keys its safe to adjust the Control bone to move the mesh just far enough away to prevent the pass-through.

(The attached .Cho has had all the above done to it)

Baked_Shirt_DC.cho

Shirt_DC_Test.prj

[fae_alba]

Hi Paul,

Dynamics could still be an alternative to cloth but as you found its not without its own settings to endlessly fiddle with! And it will never be 100% automated, you will still have to go in and tweak things at key points.

As for DC collision detection, I too gave up with it. The results were usually quite wild!

Anyway, I've attached a very simple shirt setup here which may be of interest.

This uses an idea that Nancy told me, that of using a "Master" control bone at the base of a chain of bones that are using Dynamic Constraints so that you can have better control over their behavior.

Before using the Control bone, you will first need to "Bake" the Dynamics in the Choreography.

Next play through it and note where there's any pass through of geometry.

Key the Master Control bone (without actually moving it) just before and just after geometry pass-through. Now at a suitable point between these two keys its safe to adjust the Control bone to move the mesh just far enough away to prevent the pass-through.

(The attached .Cho has had all the above done to it)

 

Mark, thanks for the examples. I downloaded the chor last night (am I blind or were my "beer goggles" on too tight and the project was not there then?!?). I looked it over briefly and noticed that the dynamics on your simple shirt are really damped down, which is exactly the behavior I was aiming for but couldn't seem to achieve. I think that sedate movement is key to controlling the shirt in the first place, and the willingness of my shirt to jump like Mexican Jumping Beans is part of my problem. So I'm going to dissect your settings, apply them to mine, and see if I can replicate the behavior. I really want this to work since animating by hand is an added worry that I was hoping to avoid.

[markw]

...(am I blind or were my "beer goggles" on too tight and the project was not there then?!?).

Sorry about that, no it's not your eyes Paul !

I meant to post the project as we'll yesterday but somehow didn't!? When I noticed today I added it to the post.

40℃ here and no air-con, makes the brain sluggish and a bit fuzzy I fear!

[fae_alba]

...(am I blind or were my "beer goggles" on too tight and the project was not there then?!?).

Sorry about that, no it's not your eyes Paul !

I meant to post the project as we'll yesterday but somehow didn't!? When I noticed today I added it to the post.

40℃ here and no air-con, makes the brain sluggish and a bit fuzzy I fear!

 

No worries!