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Fastbee

IK Dynamics mess up geometry

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I have my geometry weighted and working great if you rotate it with the joints.  Next I turn on the IK Dynamics and the geometry goes all crazy.  I'd like it to flop around like a long shred of paper with the IK, which works if I make new joints.  I'm wondering why this is not working and going all crazy though.

IK dynamics fail.zip

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something is really weird. i first thought it was because your joints aren't properly aligned (which you should always do).

i parented some cubes to the joints to be able to see what is happening, the joints are weirdly spinning around. also you get some weird jittering when you move the parent joint around. i don't know why that's happening nor how to stop it. deleted the ik, copied the joints and the mesh to a new file, applied new ik tag, same weird stuff happens. usually this should behave more or less like the example attached.

 

may i ask what you're trying to do? any sort of hair strands setup?

 

 

ikfail_not.zip

IK dynamics fail.zip

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  • Thank you everfresh for looking at it.  I remade the ik chain and re weighted and everything worked good.  Disecting the original more I found the root null to have a scale of 100.  Putting that to a scale of 1 seemed to mostly fix it.  It's strange that something like that would even matter.

     

    I am trying to get an anime style hair to flop around.  Might you have a suggestion to get better hair movement?

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    aha :slysmile: interesting... 

     

    regarding the hair solution: in my experience dynamic ik chains are hard to handle and somewhat unreliable for a task like this. especially since you need collisions probably. if you have an overseeable amount of hair strands and just need some floppy motion i have quite good experience with hair in combination with cesar voncs plugin „spline guide“and the spline rig script (also free). then you can simply animate the spline, and the hair will follow that spline with some drag and wobbly motion. if you don‘t want to animate anything manually the hair system by itself can also give quite nice results for thick hair strands, just set the hair to generate instances or splines which you then sweep.  you‘ll get self intersections though here and there, also you need to introduce some extra invisible hair colliders for your body mesh, probably mainly in the shoulder area. spline dynamics are also an option, but they tend to jitter more than the hair system. 

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  • The spline guide thing seems pretty cool.  It would be great if I needed to control more splines.  You might have noticed thought he geometry in the file I posted was in the shape of a ponytail.  That geometry is the entirety of a whole ponytail.  Having a single joint chain with some good dynamics would be my prefered way over hand keying.

     

    After some research I think below is the best solution I found.

     

    https://youtu.be/IgSm1Vsh0wA

     

    Cactus Dan's spring constraint acts quite different than C4D's in that is kind of tries to keep it's position.  It also has a mass which can make it more springy.  I'll also have to test a hybrid approach where part is joints and the rest is spline dynamics with joints tied to the position of the spline.  Dan has a cool tool to easily tie joints to splines.  Since I've decided to re weight all the hair anyway might as well try some new stuff.

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