View Full Version : Retracting/Extending Tortoise Neck

03 March 2006, 06:19 AM
Hi everyone

I've been trying very unsuccessfully to rig this tortoise I've modelled. The area of my troubles is the friggin neck which I wanted to extend way out of the shell. (The shot calls for the tortoise to take a sip of its mojito, which it cant reach without doing so)

I tried to rig it with a spline ik solver driving the whole spine and neck. By moving on of the lower Control Points way back, the whole neck and head slid nicely down the spline into the retracted position. I really like the idea of using the spline ik, as it had a really kickarse non-linear motion to it, that say a BlendShape would.

Anyway it didn't work, and my brain just cant figure a solution out, so I'll just ask.....

How do I rig a retractable/extandable neck of a tortoise????

Since my failed attempt, I modelled a 2nd version of it, only this time it's neck is in the retracted position incase it is easier to rig to extend, rather that retract.

Here are some images:
This it the Retracted neck model, with a rough wireframe to show the extent of the extended position.
And this it the side view of the first model, with the neck originally extended.

Thanks all.

03 March 2006, 09:13 AM
Weeell! You could build a neck rig with several joints which are limited along one axis to create that extension effect. You know about driven keys ("DK")? Create a loctator you can move up and down. Thatīs your driver. Now animate your neck joints from a retracted postion to an extended, by translating them along one axis. Do a key for your DK for each of the position. Now everything you have to worry about is your timing. For an added wrinkle effect, Iīd use Nurbs curves drawn onto your poly object and bound by a wrap deformer. You can animate the curves to create added animation detail and if youīre smart (and lazy :)) you might try adding the curve deformation onto a second DK or even a blend shape.

Sure itīs not as nice as a spline IK but it sure as hell will work and you should have everything handled out in, like 4 to 8 hours.

03 March 2006, 02:03 AM
i've done something similar to this, as follows.. first create your spine ik. for that matter you could just use a nurbs curve as a wire deformer in some situations, you might not even need bones. but whatever. create a cluster on each CV of your IK spline. create a series of controls, one placed over each cluster (you can just use nurbs curves for this), which use set driven keys, or constraints with more than one target, either can work fine, so that by moving one end, all the controlls in the middle automatically average their position appropriately. finally parent or constrain each cluster to the appropriate control.

in your situation you could even probably get away with a set driven key on the position of the joints.. theres a lot of ways to try it..

also, its easier to make a rig that stretches, than to compress, if you dont mind a taffy like cartoony stretching., but its going to be harder to actually make it look right when it stretches, due to the textures gonna stretch, whereas if you can figure out the rigging, and texture it to look correct when fully stretched out, compressing will be more realistic looking. personally id go for stretchy, especially if its a quick motion and you arent going to see it fully stretched out for long.

03 March 2006, 04:23 AM
just use a "schleifer style" stretchy spine type setUp...

try searching the forums or the net...

then just use the curve length relationship (that drives the stretchy joints) to drive a blendshape or 2 for the wrinkles...


03 March 2006, 05:44 AM
hi keek,...

small steps to setup stretchy bone chains.. (

hope it helps..


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