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Modular deformation & twist

August 25, 2007

Charles

I’ve been looking into curves for quite awhile now, along with waves and dynamics eventually hoping to combine all three. Along with these ive been trying to understand the rules of rigging especially layer and hierachal rigging. A lot of riggers i know dont undestand the idea of ‘layers’ in a rig. In simple terms its like a layer in photoshop but in rigs it free up a lot of issues if you keep aspects of a rig to a layer – so for example your base skeleton could be your first layer, then basic setup then twist, then deformation. So its more like layered relationships – deformation is a good example. If we can modularize deformation in a simple system we can use it all over the place.

Major deformations like  skin simulation are outside of this, but twist, stretch, compression and bulge could be driven by one system. If we treat this system as a curve the issue arises is that its not uniform so control objects along it would bunch up so we need:

  • A simplified curve, that possibly introduces horners rule (for speed)
  • Uniformity across the curve (important if the tangent vectors are straight)
  • The ability to overshoot the curve at both ends* (-0.5, 1.5)

*Why do we need this, well basically to allow for length between the points along the curve to be maintained, for example if we dont want the curve to compress the points along it need to overshoot the curve. This can be pretty simply acheived using a subdivision method. To keep a value at the same value i.e a length of 10 along the curve, all we do is divide this length by the curves length eg. 10/100. = 0.1 10/200 = 0.05. Problem comes in if the length of the curve is shorter than the defined length the ‘bucket’ inwhich t resides wouldnt exist. So you need to do some fiddling around. I’ll post some links accompanying this post.

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