FA-87207 / Physics integrator stability / Member archive

Contact impulse multiplies by the inverse mass sum · case 02

Light bodies get tiny impulses and heavy bodies are over-corrected.

Member previewVariant 2 · 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 1	`[2.092306, 0.548967]`	`[2.653378, 1.0472]`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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