Renames SkinKneeHelper to SkinJointHelper and generalises it to a list of
[parent, child] joints, so the half-angle joint technique is stated once and can
be pointed at any joint. It stays pointed at the KNEES only, and the header now
says why, because "add more joints" is the obvious next idea and it is wrong
here.
Three things were tried this round and measured, on the thigh, per vertex,
against the rest transforms:
* hip and ankle helpers as well as knees: the knee got WORSE, 0.80 -> 0.50,
and the skirt went 0.80 -> 0.72. The hip mostly swings rather than folding,
and linear-blend skinning handles a swing far better than a fold; the helper
just added another blend for nothing. Reverted.
* gating the re-weight to vertices near the leg bone chain, to keep the hip
helper off the skirt: that also excludes the OUTSIDE of the knee, which sits
further from the bone axis than the limb radius and is exactly the geometry
that needs helping. Knee went back to 0.50. Removed — with knees only there
is no skirt to protect against.
* one joint per vertex (break after the first match): kept, since a second
job would read the bones the first just rewrote.
Net result on the thigh, worst per height bucket during a jump:
y=0.60 0.80 -> 0.83 y=0.75 0.84 -> 0.84
y=0.65 0.81 -> 0.84 y=0.85 0.90 -> 0.90
and the skirt is untouched at 0.80/0.84, still free to move.
FSM tests 11/11, spawn smoke test 0 failures.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
