FA-88008 / Inverse kinematics solvers / Member archive

Continuous joints are charged the long way around · case 03

A candidate 10 degrees away across the +/-180 seam costs as if it were 350 degrees away.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Input [candidates, current, limits, weights] with joint angles in degrees. A limits entry is null for a continuous joint (distance is the shortest wrap-around difference) or [lo,hi] for a limited joint (inclusive bounds, distance is the plain difference because motion cannot pass the stop). Cost is sum w*d^2. Return [index into candidates, cost rounded 4] for the cheapest feasible candidate, earliest wins ties within 1e-9, or "none".

Why this case matters

Inverse kinematics code turns task-space goals into joint commands; a wrong branch, sign, limit or update order sends a real arm to the wrong pose.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
continuous across 180	`[1, 6241.0]`	`[0, 4.0]`	Failed

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