FA-87195 / Physics integrator stability / Member archive

Restitution threshold compares the signed velocity against a positive limit · case 05

Slow resting contacts bounce and never settle.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

solve(vn, depth, ima, imb, beta, slop, dt, e, e_thresh): one normal contact, vn<0 approaching. bias=(beta/dt)*(depth-slop) if positive; bounce=-e*vn when vn<-e_thresh. Target separating speed is max(bias,bounce); impulse=(target-vn)/(ima+imb) clamped at 0 (no pulling). Zero summed inverse mass gives [0, vn]. Return [impulse, post velocity] rounded to 6.

Why this case matters

Game and robotics physics loops depend on integrator update order, step control and stabilization terms; a wrong decision point turns a stable simulation into drifting or exploding motion.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
case 5	`[0.067113, 0.0312]`	`[0.037285, 0.0]`	Failed

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