View Full Version : stretchable "muscles" along Z' within IK?

08 August 2002, 03:59 AM
objects stretchable along Z' within IK

Lately I've been building some quick anatomic rigs with polygon objects, IK and target expressions.

I use muscles attached to different points on bones.
Then have these muscles target each other so they operate like pistons.

They look pretty cool when they are animated, But they dont make very functional bones. Because the piston action causes the mesh to cross over itself.

I am aware that I can use a comproize b/w vector weights(between the 2 part "piston muscles"). Or I can (and have) use IK to create muscles structures that bulge,..

but all of that seems overly complicated and would compromise the quality of the movement. not to mention tens of hours of work per puppet.

what I really need are bones or deformers that stretch
I am sick and tired of Gumbi.
what software alows this???(currently using cd4 but hey im flexable)
so any thoughts???

thanks alot.

08 August 2002, 04:02 AM
another illustration

08 August 2002, 11:40 AM
i dunno what app you are using but, isaw a tutorial in the messiah:animate demo specifically for that. you should check it out.

Mike RB
08 August 2002, 02:21 PM
like that?

08 August 2002, 07:00 PM

08 August 2002, 09:14 PM
show off

:wip: :applause: :drool: :eek:

08 August 2002, 04:50 AM
I think you might be interested in this

Absolute Character Tools (

it is a system for 3D Studio Max which makes the process of making muscles easy


08 August 2002, 05:28 AM
I too was teased by the clip of the arm

I set out how to work it out, and to save everybody else the hassle. Done in Max 5, but could be done in Max 4.

I have uploaded the max file, it relies on the x-pos being a way to determine the length of a bone.

the length of the bone is the distance between two dummies via max script.

And a look at to make sure it is looking at the child.

Once the bone is linked to the attachement dummy you can put the muscle/bone on the animation rig.

The squashing is automatic

Is there an easier way to do this?

08 August 2002, 10:59 PM
Thanks all,

I think Ive figured out a way to do this in C4d
besides I'm upgrading to Cinema 4-d 8 when its released,
I'll see what I can't do with it.

I must admit the absolute charactor tools look pretty cool...

though i'm not looking to do anything quite so complex .

and I don't feel like switching apps right not

I'll beat charactor anmation out of cinema, yet.

05 May 2003, 01:05 AM
Burlap_Sack: I know this is an old thread but I'm very interested in doing muscles in C4D. You say you figured somethign out? Can you share? The one thing I've tried is Xpresso to drive some muscle bones but there's a ton of trial and error.
I assume you've had more success???

05 May 2003, 05:48 AM
yes and no.

I'm pretty sure you can do this in XL8 with Xpresso functions.(unless you are still using the early bird version.)

I have a file somewhere? I did it some time ago. But its on the early bird version, which is somewhat buggy when combining target expressions with Xpresso expressions.

My freind has been doing the animation without any muscle like bones. And it looks pretty damn good. So I haven't invested too much more time into the problem. Actually to tell you the truth I traded in my G4 for a couple of sock puppets.(it was trying to suck my soul out of my eyeballs)

Anyway it may take a few days to find the file or for me to rework the solution.

05 May 2003, 08:09 AM
Mike can you share how you set up such nice deformations man?

05 May 2003, 12:42 PM
Burlap_Sack: Yeah...i know what you mean. I have version 8, Soft IK and all that. Still seems like a lot of work. LOTS of trial and error. I don't mind the extra work, but trail and error can take forever to figure things out.

I appreciate your time and any rigs you can dig up....

Sock puppets...yes...sock puppets...that may be the way to go. I too have a G4...that's laghing at me...

05 May 2003, 10:23 PM
Sheep, I think Mike used a combination of the Muscle Expression in Lightwave that makes a bone stretch along its Z axis to meet the IK target as well as affects its thickness based on its length.

After that, defined weight maps will limit the bone's effect to just the right region of the mesh.

06 June 2003, 06:10 AM
thanks samhodge, this is excellent muscle reference for building my rig. cheers :P

06 June 2003, 05:33 PM
Anybody create any examples of this kind of muscle movement in Cinema 4D??

07 July 2003, 03:36 PM
hi guys,

i'm looking into ways to create a muscle rig for my MSc project and haven't really heard much this technique. can someone please clarify the theory/process of this technique for me please? this technique seems to use stretchy bones to wieght the skin thus giving an impression of muscle deformation without the use of underlying muscle geometery to influence skin deformation, is this right? also are the stretchy bones on the same heirachy as the main rigid rig?

07 July 2003, 04:53 AM
yup you have got it right

as far as the hierarchy goes its really up to you
you might have a mixture of hierarchy and postion and orientation contsraints and postions and rotation scripts


07 July 2003, 09:24 AM
cheers mate, i'm going to give it a try. maybe i'll use it for simple longitude stretch muscles and use blend shapes for more complex muscles.

07 July 2003, 04:40 PM
Any muscle that stretches loses thickness so as to retain its volume. You might want to consider a muscle bone setup that loses thickness as it elongates.

Blendshapes and morphs are good for complex regions like lips and shoulders, but if a simple bone works for a simple bicep, then it's just extra work to rebuild your model at each extreme.

Just my opinion.

07 July 2003, 08:17 PM
actualy i`m working on a muscle plugin for maya that use a nurbs to simulate a muscle, it perserve the position of the origin and the insercion of the muscle and the volume.

you can try in highend (

12 December 2004, 07:51 AM
Bam! i was looking around for a way to create stretchy bones so i could do muscles and i read something in the discreet forums that reminded me of mikes bone picture farther up in this post. i built something similar the other day but since i did it in max 6 i dont know if all of you guys will be able to copy it.

step one build a normal 3 bone arm (3rd is the end bone) with a limb solver.
step two build another bone where the bicep will be.
step 3 create 2 dummies one at the base of the bicep bone and the second at the end bone for the bicep
step 4 select the bicep bone and open up bone tools. under bone tools go to the object properties roll out and unckech freeze length. then selecte the stretch type "squash"
step 5 now select the bicep bone and assign a position and orientation constraint to the dummy at its base.
do the same for the end bone
link the dummies to the upper and lower arms bones with the limb solver on them.
Bam! you now have a squashing bicep that moves with your arm bones!!!

note: if the orientation constraint appeared to mess up your bicep bone just rotate the dummies until it goes back to looking normal.

hope that you were able to understand this without pictures

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