Fix computation of alpha channel for transparent objects#110
Merged
ManifoldFR merged 2 commits intoSimple-Robotics:mainfrom Feb 26, 2026
Merged
Fix computation of alpha channel for transparent objects#110ManifoldFR merged 2 commits intoSimple-Robotics:mainfrom
ManifoldFR merged 2 commits intoSimple-Robotics:mainfrom
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…in fragment shader + weight applies to accum.a, not to revealage (account for change in blend formula)
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Fix WBOIT transparency so that transparent objects over a transparent background have correct alpha in PNG output, and improve color reconstruction in the composite pass.
Wrong revealage:
output.reveal = 1.0 - alpha * weightproduces negative values for most materials (whenalpha * weight > 1), which clamp to 0 in theR8_UNORMtexture format. The multiplicative blend then leaves the revealTexture unchanged at its clear value of 1.0, so the composite always computesalpha = 1 - reveal = 0. Fixed tooutput.reveal = alpha.Wrong accumulation denominator: accum.a = alpha caused the composite to reconstruct color * weight instead of color. Fixed to
accum.a = alpha * weight.Before (click the picture; on browsers which support transparency in PNG the robot body will be blank (black))
After (robot body is properly transparent)
There were already changes to WBOIT in #109 but they weren't enough.
@pierfabre