Avoid sqrt of negative discriminants in MJX ray quadratics - #3513
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sylvesterkaczmarek wants to merge 1 commit into
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Avoid sqrt of negative discriminants in MJX ray quadratics#3513sylvesterkaczmarek wants to merge 1 commit into
sylvesterkaczmarek wants to merge 1 commit into
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Summary
Prevent
_ray_quadfrom takingsqrtof a negative discriminant before no-intersection masking is applied.The current code computes
jp.sqrt(det)first and only afterward replaces results with infinity whendet < mjMINVAL. For negative discriminants, the square root therefore produces NaNs unnecessarily.Clamp only the square-root input to zero:
jp.sqrt(jp.maximum(det, 0))The existing
det < mjMINVALcondition still controls the returned no-intersection result, so positive-discriminant behavior and the existing threshold are unchanged.Adds a focused regression test for a quadratic with a negative discriminant, asserting both roots are
infrather thanNaN.The original diagnosis was reported in closed, unmerged PR #2895 by @zhangbaozhe. This is a narrower reimplementation on current
main.Validation
Final branch is based on current
main, with one implementation line and one focused regression test.The MJX runtime test was not executed locally because the required MuJoCo/JAX Python environment is not installed here.