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Thread: Adjust height/length of bones and mesh together

  1. #1
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    Adjust height/length of bones and mesh together

    I have a human model
    I want to scale/lengthen different sections of it such as thigh to shin ratio or widening the torso
    I understand the use of shape keys to accomplish some parts
    I have a human rig
    I want the rig to transform at appropriate sections along with the human model and keep its animations relatively intact

    I have played around with bone constraints and parenting, and coming up with something similar to the muscle system setup…

    My goal is to create a character model that can be customised like in game character creation systems but I am having trouble working out how to implement the height/length of bones without using ‘edit mode’, and have the mesh copy. (I am guessing drivers are a key factor in this.)

    For example:
    If I had an armature setup of human legs with a walk cycle; how would I change the position of the knee in the armature and have the human legs mesh knee move with it while keeping the walk cycle? Would I need multiple rigs?



  2. #2
    Member Anthony Forwood's Avatar
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    Your mesh will normally stretch when you scale a bone, so what's the problem?



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    I think maybe I am over-thinking it...?

    So, if I adjust a joint in pose mode the mesh will follow along in that place and keep the animation I have created? 'Cause I know if I key in on the rotations of the joint in pose mode then adjust the placement of a joint in edit mode, the animation plays out well. But doing it this way means editing the mesh separately...

    I am just not understanding something or I do but don't know how to implement it...



  4. #4
    Member Anthony Forwood's Avatar
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    You're trying to edit your bones AFTER having added the mesh, which when I tried, gave me immense problems until I finally gave up and just detached the mesh first. It's far easier. If you already have vertex groups set up and assigned to bones, they'll remain intact for you, so it shouldn't mean starting all over.



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    When I scale a bone in pose mode the mesh follows, but when I play the walk cycle the scale doesn't remain and makes the animation look wonky...



  6. #6
    Member Anthony Forwood's Avatar
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    Pose mode is for posing. Edit mode is for editing. You will have problems with the mesh if you confuse the two and think you can edit in pose mode.



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    I know the difference... I'm comfortable with modelling, rigging and animating, and the use of shape keys and drivers for facial rig as well as 'fattening'/'thinning' body parts. I'm really having trouble in trying to figure out how to adjust heights or joints positions with mesh... Just can't wrap my head around it.



  8. #8
    hum,
    It's not as easy as it sound.
    I think it can work but the result may vary depending on how different your characters are, how you animate them , and how much drifting in animation is allowed.

    In fact it's done with motion capture data, you adapt one animation to a character with different proportions. It's called animation retargetting.
    But I think mocap data works only with rotations, so it may be easier to remap that to another rig. Also when retargeted the animation is cleaned by hand. Because of course if there are many differences things don't match very well.

    Also you can look at CGCookie's Flex rig, that is a rig that can change shape and you can make various characters from it. You can see how they deal with that issue. (I haven't tried it myself)

    Maybe you've raised the bar too high. If that's possible, you can just make a rig that can change shape easily (a kind of mega-strecheable/scalable rig) , so the workflow could be like this.
    1/ You create a new character by adapting shapes keys, bone scale ect...
    2/ Then you freeze the rig, (apply pose as rest pose) , reset stretch , transforms ect...
    3/ Then you reuse animation and make tweaks by hand if it's too different and the animation doesn't work well anymore.

    Anyway it's an interesting case to study , good luck



  9. #9
    Member YAFU's Avatar
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    Originally Posted by Nikkita View Post
    When I scale a bone in pose mode the mesh follows, but when I play the walk cycle the scale doesn't remain and makes the animation look wonky...
    Hi.
    So, did your walk cycle need to keyframe "scale" in bones for some reason?
    If you only keyframe LocRot, then if you scale bones in pose mode they should keep the new sizes when play animation.

    It would also be good to share a basic rig in blend file, trying to better explain what it is what you want to achieve. Here for example in description there is a model that you could use (I guess there would be no problem with licenses, but not sure):
    https://www.youtube.com/watch?v=sTo4adwvulE
    Last edited by YAFU; 13-Sep-17 at 22:31.
    Be patient, English is not my language.



  10. #10
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    Originally Posted by sozap View Post
    hum,
    It's not as easy as it sound.
    I think it can work but the result may vary depending on how different your characters are, how you animate them , and how much drifting in animation is allowed.

    In fact it's done with motion capture data, you adapt one animation to a character with different proportions. It's called animation retargetting.
    But I think mocap data works only with rotations, so it may be easier to remap that to another rig. Also when retargeted the animation is cleaned by hand. Because of course if there are many differences things don't match very well.

    Also you can look at CGCookie's Flex rig, that is a rig that can change shape and you can make various characters from it. You can see how they deal with that issue. (I haven't tried it myself)

    Maybe you've raised the bar too high. If that's possible, you can just make a rig that can change shape easily (a kind of mega-strecheable/scalable rig) , so the workflow could be like this.
    1/ You create a new character by adapting shapes keys, bone scale ect...
    2/ Then you freeze the rig, (apply pose as rest pose) , reset stretch , transforms ect...
    3/ Then you reuse animation and make tweaks by hand if it's too different and the animation doesn't work well anymore.

    Anyway it's an interesting case to study , good luck
    Thank you, I've been hoping for this type of direction. I just checked out the 'flex rig' and it's extremely close to what I am after. Can't believe I've never known about it until just now... Though I would love to create my own from the ground up like I've done with everything else. Thank you again, you've helped out heaps.



  11. #11
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    Originally Posted by YAFU View Post
    Hi.
    So, did your walk cycle need to keyframe "scale" in bones for some reason?
    If you only keyframe LocRot, then if you scale bones in pose mode they should keep the new sizes when play animation.
    Ah, I think I may have been keyframing 'scale' in there...

    It would also be good to share a basic rig in blend file, trying to better explain what it is what you want to achieve. Here for example in description there is a model that you could use (I guess there would be no problem with licenses, but not sure):
    https://www.youtube.com/watch?v=sTo4adwvulE
    I was thinking I should do that. Oh, thanks for the link. It will come in handy



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