aleleba/effectcraft
1
0
Fork 0
mirror of https://github.com/storytold/effectcraft.git synced 2026-10-30 13:08:07 -06:00
Code Issues Packages Projects Releases Wiki Activity

Blend modes: classic modes fade with opacity and HDR modes keep over-range values, as in After Effects (#494)

Browse Source 
Measured against After Effects at 32 bpc:

- Classic Color Dodge, Classic Color Burn and Classic Difference at partial opacity: AE
  fades the source toward the mode's neutral colour (0 for Dodge and Difference, 1 for
  Burn) by the opacity and applies the classic formula at full strength (b / (1 − k·o),
  |b − k·o|, 1 − (1 − b) / (1 − k·(1 − o))). We mixed the full-strength result by opacity:
  up to 45/255 off on ordinary 0–1 footage.
- Overlay, Exclusion, Luminosity, Color Burn and Classic Color Burn keep their plain formula
  for values above 1 (HDR passes). They were missing from `supports_hdr`, so their inputs
  were clamped to 0–1 (Exclusion was up to 208/255 off); Classic Color Burn also clamped
  its result at 0, where AE keeps negative values.

The CPU blend (color::blend_pixel) and the GPU kernel (common.wgsl) change together.

Tests: the reporter's formulas for each case (blend.rs); the CPU/GPU parity test of every
blend mode at every bit depth (over-range values, 70 % opacity) passes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QiAJeFttZp83Fh7YuzAR5f
This commit is contained in:
Claude
2026-10-10 20:51:24 +00:00
parent 1c9b5f1828
commit ecb2cf1d32
2 changed files with 75 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
crates/gpu/src/shaders/common.wgsl
+13 -3
View File
@@ -235,7 +235,7 @@ fn separable(mode: u32, cb: f32, cs: f32) -> f32 {
if (cs <= 0.0) {
return 0.0;
}
return max(1.0 - (1.0 - cb) / cs, 0.0);
return 1.0 - (1.0 - cb) / cs;
}
case 7u: { return max(cb + cs - 1.0, 0.0); }
case 9u, 14u: { return cb + cs; }
@@ -343,7 +343,7 @@ fn non_separable(mode: u32, cb: vec3<f32>, cs: vec3<f32>) -> vec3<f32> {
fn supports_hdr(mode: u32) -> bool {
switch mode {
case 0u, 1u, 2u, 3u, 4u, 7u, 8u, 9u, 10u, 11u, 14u, 15u, 23u, 24u, 26u, 27u, 32u, 33u, 34u, 35u, 36u, 37u: { return true; }
case 0u, 1u, 2u, 3u, 4u, 5u, 6u, 7u, 8u, 9u, 10u, 11u, 14u, 15u, 16u, 23u, 24u, 25u, 26u, 27u, 31u, 32u, 33u, 34u, 35u, 36u, 37u: { return true; }
default: { return false; }
}
}
@@ -388,8 +388,18 @@ fn blend_pixel(mode: u32, dst: vec4<f32>, src: vec4<f32>, noise: f32) -> vec4<f3
cs = clamp(cs, vec3<f32>(0.0), vec3<f32>(1.0));
cb = clamp(cb, vec3<f32>(0.0), vec3<f32>(1.0));
}
let b = non_separable(mode, cb, cs);
let ao = sa + da - sa * da;
// Classic Color Dodge / Difference (neutral 0) and Classic Color Burn (neutral 1): the
// source fades toward the neutral colour by its coverage, then the formula applies.
if (mode == 13u || mode == 24u || mode == 6u) {
var neutral = 0.0;
if (mode == 6u) {
neutral = 1.0;
}
let bc = non_separable(mode, cb, neutral + sa * (cs - neutral));
return vec4<f32>((1.0 - da) * src.xyz + da * bc, ao);
}
let b = non_separable(mode, cb, cs);
return vec4<f32>((1.0 - da) * src.xyz + (1.0 - sa) * dst.xyz + sa * da * b, ao);
}