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Medillus    2

Hi everyone,

I'm a new convert to C4D (Maya for 1 year, 3ds max for 2 years) and I love it. I'm currently working on a rig for a spine model (link below) so I can animate pathology such as scoliosis and kyphosis. 

 

The rig needs to be be manipulative enough that I can control the spine without warping any of my meshes, so I've opted to make the actual mesh into my joints and bones. 

  • Vertebrae=Bones
  • Discs=Joints 

 

So far i've tried a basic ik rig with a single goal, and an ikspline. I think the ik spline is the route I want to take, because it seems to allow the most manipulative power, but some odd warping takes place when I apply it to the rig. My vertebrae get all rotated in odd ways once I link the spline and the end joint to the ikspline tag. I think it has to do with the alignment of each disc (joint) along the spline, but i'm not quite sure how to fix that. Work In progress.

 

I'm using the amazing skeleton model from Badking: http://www.badking.com.au/site/shop/human/skeleton-model-setby-benjamin-wilson/

Images of my current issue are below, if anyone has any suggestions or if I've sparked inspiration

 

Medillus

 

ikSplineSpine.png

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digitvisions    51

Hi, there are few things you could try experimenting with, first try the various settings of the spline; B spline, Akima, and so on. Also make sure that the axis of your vertebrates is centred.

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Medillus    2
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  • Digitvisions--

    Thanks! I hadn't tried changing the settings of the spline yet--unfortunately it looks like bezier is our best option.  The others alter the original position even more

    The joint axis are centered (I went through and aligned-axis-to-center each); I'm wondering if their initial rotation (resting position of the spine) has anything to do with it.  Since everything is naturally not lined up in a straight column, maybe when they are linked to the spline they try and adjust to match the spline axis orientation...Because in my tests (with just some block and sphere primitives aligned in a straight column) I don't get this problem.

     

    I'm wondering if there was a way for me to also align the axis rotation with to match the spline orientation, aside from me lining up the spline as close as possible manually

     

     

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    digitvisions    51

    Hi, What you need to ask yourself is what kind of animations you need to get from your rig. Sometimes it's the simplest setup that will get you there. For example; if you just need a nice even curvature of the spine in one or more directions

    xpersso setup via a data user conectet to a slider will do it. if you need more precise manipulation of each vertebrates ,then you could do with out the spline and just rotate the joints individually.

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    everfresh    163

    spline ik setups in c4d can be tricky. it's important to have all joints in your ik-chain pointing in the same direction. you can have initial curvature in there, but the joint all need to point in the same direction in z. also for spline iks in c4d i always introduce an up vector usually a null object for all the joints to align to. you can also have multiple up vectors and blend the joint orientations between them to have full control over the twist. also get your spline ik setup going first, and then bind your geometry (or constrain or parent it)...

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    Medillus    2
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  • 4 hours ago, digitvisions said:

    Hi, What you need to ask yourself is what kind of animations you need to get from your rig. Sometimes it's the simplest setup that will get you there. For example; if you just need a nice even curvature of the spine in one or more directions

    xpersso setup via a data user conectet to a slider will do it. if you need more precise manipulation of each vertebrates ,then you could do with out the spline and just rotate the joints individually.

    Thanks! the goal is to get something that can show the mobility of the spine and can be used over and over again for general production. I definitely think xpresso will ultimately be the way to go, if I plan to hand this off to someone else I'd like them to be able to use it intuitively. Sliders will help with that--I did think I needed to get the general rig working before i moved into xpresso? 
    But I assumed it was similar to the Wiring Parameters feature in 3Dsmax, so I hadn't moved on to that step yet 

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    Medillus    2
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  • 4 hours ago, everfresh said:

    spline ik setups in c4d can be tricky. it's important to have all joints in your ik-chain pointing in the same direction. you can have initial curvature in there, but the joint all need to point in the same direction in z. also for spline iks in c4d i always introduce an up vector usually a null object for all the joints to align to. you can also have multiple up vectors and blend the joint orientations between them to have full control over the twist. also get your spline ik setup going first, and then bind your geometry (or constrain or parent it)...

    hmm i need to play around with this idea more. I constrained each joint to a single up vector (null) and it tilted them around a bit. So instead, I created nulls from each joint mesh, parented each under their respective nulls and constrained those nulls to an up vector. (I can already tell I probably over-complicated this). 

    I then made those nulls, with the up vector constraint, my joints for the ik Spline. It seemed to be behaving differently so I had my hopes up, but once everything was hooked up I got the same strange reorientation of each object. 

     

    What do you mean by blend the joint orientations? Thanks--greatly appreciated 

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    everfresh    163

    take a look at the file... notice that the up-vector constraints have multiple targets so the joint rotations can blend between them. it's always a bit tricky to get the priorities right, the c4d spline ik isn't very intuitive, and i still have a hard time wrapping my head around it every time i use it. i wish we had the possibilities like in maya here.

    spine.c4d

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    Medillus    2
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  • 15 hours ago, everfresh said:

    take a look at the file... notice that the up-vector constraints have multiple targets so the joint rotations can blend between them. it's always a bit tricky to get the priorities right, the c4d spline ik isn't very intuitive, and i still have a hard time wrapping my head around it every time i use it. i wish we had the possibilities like in maya here.

    spine.c4d

     

    This is great, and worked perfectly when i applied it to the spine model. thanks so much for the guidance!

      Luckily or unluckily I never rigged in maya so i'm not pining for some past usability... but with a few more handles it looks like i'll have the mobility I need for future projects. excited to hook this up with xpresso and hopefully post some WIPs once we purchase the program! (currently on demo) 

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