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Arrrg! Kinematics and bone flippy floppy


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#1 Darthlister

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Posted 30 March 2014 - 05:50 PM

Hi all. What's the best way to avoid wantint to putt all your eyebrow hair out when having tow characters physicallly interact? Using kinematics to keep them connected, but running into my models turning into rubber bands if I move one or the others juuust so... Rich

#2 robcat2075

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Posted 30 March 2014 - 06:28 PM

It is certainly doable. Show us what you are doing.

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#3 Darthlister

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Posted 06 April 2014 - 05:38 PM

It is certainly doable. Show us what you are doing.

Take a look. Firefall is

1. grabbing ROMs hand/wrist
2. pulling him in
3. flinging him toward the wall
strugglecap.JPG

the full chor is really huge, so hopefully this'll give a hint of what's going on.

Having a hard time understanding how the bones relate to each other while in a K chain and how to avoid the arm twisting into
a pretzel whenever char 1 moves...

Rich

#4 robcat2075

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Posted 06 April 2014 - 06:10 PM

Firefall is

1. grabbing ROMs hand/wrist
2. pulling him in
3. flinging him toward the wall
strugglecap.JPG



For this particular moment I would constrain Redguy's IK hands to the relevant geometry bone of GrayGuy that they appear to be grabbing, then you animate GrayGuy's body and arms to move AS IF they were being moved by RedGuy and RedGuys' arms will follow along.

When the moment comes that RedGuy lets go of GrayGuy then you unconstrain RedGuy's IK hands from GrayGuy and animate them normally.

A fight scene might have many such exchanges depending on who is grabbing who.

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#5 Darthlister

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Posted 20 April 2014 - 09:21 AM

Firefall is

1. grabbing ROMs hand/wrist
2. pulling him in
3. flinging him toward the wall
strugglecap.JPG



For this particular moment I would constrain Redguy's IK hands to the relevant geometry bone of GrayGuy that they appear to be grabbing, then you animate GrayGuy's body and arms to move AS IF they were being moved by RedGuy and RedGuys' arms will follow along.

When the moment comes that RedGuy lets go of GrayGuy then you unconstrain RedGuy's IK hands from GrayGuy and animate them normally.

A fight scene might have many such exchanges depending on who is grabbing who.

Yeah. I guess what I'm having a hard time getting my head around is where exactly the kinematic connection is. For example--left hand on greyguy to left hand on redguy--at 100%, how do those bones interact? where is the connection? From thin end of one to thick end of another? Is the bone with the constraint, the "parent" in the chain?

Thankee- sai,
Rich

#6 robcat2075

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Posted 20 April 2014 - 11:02 AM

Yeah. I guess what I'm having a hard time getting my head around is where exactly the kinematic connection is. For example--left hand on greyguy to left hand on redguy--at 100%, how do those bones interact? where is the connection? From thin end of one to thick end of another? Is the bone with the constraint, the "parent" in the chain?



For example--left hand on greyguy to left hand on redguy--at 100%, how do those bones interact?


If the left hand of Grey guy is Kinematic Translate To constrained to the lefthand of Red guy, then lefthand of Redguy is what is in control, leading the lefthand of Grayguy around. The lefthand of GreyGuy, in turn, is what is leading its left arm around.

where is the connection? From thin end of one to thick end of another?


Most constraints are created with an "offset" by default so there doesn't have to be actual visible contact between a constrained bone and its target.

Is the bone with the constraint, the "parent" in the chain?


Other way 'round... the bone that is that is chosen as the target of the kinematic Translate To constraint is the leader.

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#7 robcat2075

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Posted 20 April 2014 - 11:17 AM

Note major correction above... I confused Kinematic and Translate To Constraints. In practice, if you want to constrain something to a freely moving object like a hand you will need both a Translate To constraint and an Orient Like constraint

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#8 robcat2075

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Posted 20 April 2014 - 12:28 PM

Here is a demonstration of attaching a grey hand to a red hand Attached File  clip3520HandToHand.mov   27.76MB   97 downloads Sample PRJ before the constraints are done. Attached File  HandToHand03.prj   243.13KB   107 downloads

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