Implements the algorithm the README has listed as "still to come" since v0.
A 3x3x5 lattice of control points encloses the car; an impact shoves nearby
points inward and mesh vertices follow via inverse-distance weighting
(W_i = 1/||p_j - c_i||^alpha, alpha=2), clamped to the PDF's bounding-box
safety limit so panels crumple rather than fold through themselves.
The weights depend only on original positions, so they're precomputed once per
car at setup -- each impact is then a plain weighted sum at 0.3 ms, with no
per-frame cost at all. Meshes are deep-copied per car so deforming one Kingswood
doesn't dent every other Kingswood sharing the GLB.
Measured on the Lazza: a hard nose-on hit displaces 11.9 cm, accumulating to
18.2 cm over repeat hits, well inside the 42 cm clamp. Only the player and
rivals carry a deformer; traffic and parked cars stay plain bodies.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
