Bug fix: smoothstep should emulate glsl behavior in degenerate cases#2915
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bhouston wants to merge 2 commits into
Open
Bug fix: smoothstep should emulate glsl behavior in degenerate cases#2915bhouston wants to merge 2 commits into
bhouston wants to merge 2 commits into
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Apply the inverted/degenerate smoothstep fallback component-wise for vector2, vector3, and vector4 to match the float fix across all smoothstep nodedef variants.
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See #2914 (comment) for recommendations on resolving this category of undefined behaviors through new specification proposals, so that our per-language implementations have an unambiguous reference to match. |
Contributor
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fwiw, there is already a doc change proposal for this, but old by now: AcademySoftwareFoundation/OpenShadingLanguage#1851 |
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Like most of my PRs I noticed via https://material-fidelity.ben3d.ca that smooth step when the bounds are inverted does not replicate glsl behaviour. This PR fixes that.
Summary
Update the float
smoothstepimplementation ingenoslto handle degenerate/inverted bounds explicitly.ND_smoothstep_floatnow uses:smoothstep(low, high, in)whenhigh > lowhigh <= low: hard step athigh(in < high ? 0.0 : 1.0)Why
For inverted bounds,
smoothstepbehavior can diverge across backends due to undefined/implementation-dependent handling. This caused visible mismatch inmaterialx-oslfor degenerate node tests.Making the fallback explicit in
genoslimproves determinism and cross-renderer consistency for these edge cases.Validation
Renders from OSL, Metal and GLSL now match: