Nicholas ButzkeandClaude Opus 4.8
050011666c
This is the leg squashing. It was at the KNEE, and every previous measurement missed it because they averaged a ring of vertices, which hides a collapse that only affects part of the ring. Measured per vertex instead, against an exact rest-transform baseline: 532 of Taila's leg vertices lose more than 20% of their distance from the bone axis and the worst lose 40%, all at y=0.54 — exactly the knee — and worst in the air pose. That is "squashing while running or jumping, easy to see from the side". Cause is inherent to linear-blend skinning: it averages TRANSFORMS, not shapes. A vertex half on the thigh and half on the shin is placed at the average of two rotations, and at a hard bend that average falls well inside the leg, pinching it to a ribbon. SkinKneeHelper adds a bone at each knee, parented to the thigh and holding the shin's rest transform, driven every frame to HALF the shin's rotation from inside the skeleton's modification pass. Blend-zone vertices are re-weighted off the thigh/shin pair and onto the helper, taking equal weight from each side and reusing the slot that falls to zero — so no extra influence slot is needed and the weights still sum to exactly 1. The sharpest blend any vertex now sees is half the knee angle, and halving the angle roughly quarters the collapse. Result: vertices losing more than 20% of their radius go from 532 to 0 on the body. The worst anywhere is now 0.79, on the outline shell, which is hidden. Verified visually too, legs rendered bare from the side through rest, run and jump: knees hold their volume and the bind is intact. FSM tests 11/11, spawn smoke test 0 failures, Miku unaffected. Co-Authored-By: Claude Opus 4.8 <[email protected]>
