Without a Fill Mask, After Effects turns the layer into the fill colour and
applies Opacity to its alpha; nothing of the original shows through. AE 2026
renders Fill (0, 0.5, 1) at Opacity 50 % on a Gradient Ramp over a red solid
as premultiplied (0, 0.251, 0.502) at alpha 0.502 at every pixel; EffectCraft
mixed the fill with the ramp (mean difference 95.5/255), now within 1/255,
CPU and GPU. Invert fills the transparent part the same way. With a Fill
Mask the mix with the original is unchanged (not measured). Lottie's fill
effect (colour, alpha x opacity) now plays the same in EffectCraft.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>