Timewarp: retime the layer's source without the effects above it, as After Effects

After Effects' Timewarp reads the layer's source (with its masks) at the
retimed times and ignores the effects applied before it: a red solid with a
Gradient Ramp and then Timewarp (Speed 25) renders as the red solid in AE
2026 (EXPORTER e2 read-back). EffectCraft retimed the layer with its
effects (mean difference 127.5/255 over the comp), now identical (0, CPU and
GPU). Echo, Posterize Time and the other time effects keep reading the
effects before them, as measured before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/effects/src/time_fx.rs

@@ -4,8 +4,10 @@
 //! These read the layer at *other* layer times through [`EffectHost::self_at`]: its source with
 //! its masks and the effects applied before them, as After Effects renders them (SceneYard:
 //! Echo after CC Particle Systems II echoes the fireworks, not the black solid under them;
-//! Posterize Time after Turbulent Displace steps the displacement). Without a host (tests,
-//! thumbnails) they pass their input through.
+//! Posterize Time after Turbulent Displace steps the displacement). Timewarp is the exception:
+//! it retimes the layer's source with its masks and ignores the effects above it (After
+//! Effects 2026: a red solid with a Gradient Ramp and then Timewarp shows the red solid).
+//! Without a host (tests, thumbnails) they pass their input through.
 //!
 //! Timewarp's Pixel Motion estimates block-matching optical flow between neighbouring frames
 //! ([`effectcraft_raster::flow`]); Pixel Motion Blur averages sub-frame samples.
@@ -163,15 +165,21 @@ struct Frames {
     imgs: Vec<Image>,
 }
 
-/// Fetch the layer (source + masks) at layer times `times`. `None` without a host.
+/// Fetch the layer (source + masks + the effects before this one) at layer times `times`.
+/// `None` without a host.
 fn fetch(ctx: &EffectCtx, times: &[f64]) -> Option<Frames> {
+    fetch_with(ctx, times, usize::MAX)
+}
+
+/// [`fetch`] with the first `effects` effects of the stack only (0: source and masks).
+fn fetch_with(ctx: &EffectCtx, times: &[f64], effects: usize) -> Option<Frames> {
     let host = ctx.env.host?;
     // Dedupe times (sub-microsecond differences are the same frame).
     let mut uniq: Vec<i64> = times.iter().map(|t| (t * 1e6).round() as i64).collect();
     uniq.sort_unstable();
     uniq.dedup();
     // Every effect before this one (the host bounds the count to them).
-    let bufs: Vec<(i64, Option<Buf>)> = uniq.iter().map(|&k| (k, host.self_at(k as f64 / 1e6, usize::MAX))).collect();
+    let bufs: Vec<(i64, Option<Buf>)> = uniq.iter().map(|&k| (k, host.self_at(k as f64 / 1e6, effects))).collect();
     let first = bufs.iter().find_map(|(_, b)| b.as_ref())?;
     let scale = first.scale;
     // Union of every frame's extent in layer pixels (offset = where layer (0,0) sits).
@@ -786,7 +794,8 @@ pub fn timewarp_plan(ctx: &EffectCtx) -> Option<TimewarpPlan> {
     let (instants, times, fps) = timewarp_instants(ctx);
     let method = ctx.params.e("method");
     let one = method > 0 && ctx.params.b("tuning/buildFromOneImage");
-    let fr = fetch(ctx, &times)?;
+    // The source with its masks, without the effects above Timewarp.
+    let fr = fetch_with(ctx, &times, 0)?;
     let pm = PixelMotion::from(ctx, fr.grid.scale);
     let mattes = fetch_layer(ctx, "matteLayer", &times, &fr.grid);
     let warps = fetch_layer(ctx, "warpLayer", &times, &fr.grid);
@@ -1016,8 +1025,8 @@ mod tests {
             None
         }
         fn self_at(&self, t: f64, effects: usize) -> Option<Buf> {
-            // Time effects see every effect before them.
-            assert_eq!(effects, usize::MAX);
+            // Time effects see every effect before them; Timewarp only the source and masks.
+            assert!(effects == usize::MAX || effects == 0, "{effects}");
             let v = if self.static_layer { 0.4 } else { t as f32 };
             Some(Buf { img: Image::filled(6, 4, [v, v, v, 1.0]), offset: [0.0; 2], scale: 1.0 })
         }
@@ -1028,6 +1037,32 @@ mod tests {
         run_fx(id, vals, Image::filled(6, 4, [0.9, 0.0, 0.0, 1.0]), t, env)
     }
 
+    /// After Effects 2026: Timewarp retimes the layer's source (with masks) and ignores the
+    /// effects above it; Echo keeps them.
+    #[test]
+    fn timewarp_reads_the_source_without_the_effects_above_it() {
+        struct Asked(std::sync::Mutex<Vec<usize>>);
+        impl EffectHost for Asked {
+            fn layer(&self, _: u64, _: bool) -> Option<LayerPixels> {
+                None
+            }
+            fn audio(&self, _: u64, _: f64, _: usize, _: u32) -> Option<Vec<f32>> {
+                None
+            }
+            fn self_at(&self, _: f64, effects: usize) -> Option<Buf> {
+                self.0.lock().unwrap_or_else(std::sync::PoisonError::into_inner).push(effects);
+                // The source (effects 0) is red, the layer with its effects green.
+                let c = if effects == 0 { [1.0, 0.0, 0.0, 1.0] } else { [0.0, 1.0, 0.0, 1.0] };
+                Some(Buf { img: Image::filled(6, 4, c), offset: [0.0; 2], scale: 1.0 })
+            }
+        }
+        let host = Asked(std::sync::Mutex::new(vec![]));
+        let env = EffectEnv { host: Some(&host), frame_rate: 10.0, comp_time: 1.0, ..Default::default() };
+        let out = run_fx("ec.time.timewarp", &[("speed", num(25.0))], Image::filled(6, 4, [0.0, 1.0, 0.0, 1.0]), 1.0, env);
+        assert_eq!(out.img.get(2, 2), [1.0, 0.0, 0.0, 1.0]);
+        assert!(host.0.lock().unwrap_or_else(std::sync::PoisonError::into_inner).iter().all(|&e| e == 0));
+    }
+
     #[test]
     fn posterize_time_holds_frames() {
         let h = Clock { static_layer: false };

docs/effects-parity.md

@@ -44,7 +44,7 @@ corpus compares renders, each effect is assumed to differ somewhere, and users k
 | Simulation | 18 | 18 | Particle Playground lacks Particle Exploder, text particles, ephemeral mapper; CC Particle World camera fixed (#397) |
 | Stylize | 25 | 25 | Motion Tile output size (#369) |
 | Text | 2 | 2 | — |
-| Time | 8 | 8 | #535 (Pixel Motion Blur, Vector Detail) is closed |
+| Time | 8 | 8 | Timewarp retimes the layer's source and masks without the effects above it, as After Effects 2026; #535 (Pixel Motion Blur, Vector Detail) is closed |
 | Transition | 17 | 17 | — |
 | Utility | 9 | 7 | — |
 
@@ -64,6 +64,7 @@ the GPU is performance, not parity.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-19 | minor | Timewarp ignores the effects above it (source and masks only), measured against After Effects 2026 |
 | 2026-10-12 | minor | Parameters 3,014 to 3,017 (effects.md); #303, #514, #526, #533–#536 marked closed instead of pending |
 | 2026-10-12 | minor | Effect colour labels (26.5) added in Effect Controls |
 | 2026-10-12 | minor | Tint's Swap Colors button and agent-drivable command (#963); undo/redo, instance targeting, animated layer-time edits and invalid-input tests |