Levels: channel controls before RGB, "Off for 32 bpc Color" unclipped in 32 bpc, as After Effects

After Effects 2026 in a 32 bpc project, Levels (Individual Controls) with RGB
(0.1, 0.9, gamma 1.5, 0.05, 0.95), Red Gamma 0.8, Green Input White 0.8 and
Blue Output Black 0.2 on grey steps 0..255 (case 904 E07): every step matches
"each channel's controls, then the RGB controls" with nothing clipped
(values below Input Black end below Output Black, above Input White above
Output White). EffectCraft ran RGB first and clipped "Off for 32 bpc Color"
(it could not see the bit depth): up to 27/255 off on 95 % of the grid; now
0 grid points off, max 1/255, CPU and GPU.

EffectEnv gains float_depth (the renderer sets it for 32 bpc projects), so
"Off for 32 bpc Color" clips in 8 / 16 bpc projects as before. Unclipped
values below 0 take the gamma mirrored through 0. Plain Levels keeps its
order (its channel controls were not measured); its clipping follows the same
rule. EffectCraft's own projects default to 8 bpc and are unchanged.

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

crates/gpu/src/deferred.rs

@@ -252,6 +252,7 @@ pub(crate) fn chain_key(chain: &[FxStep], buf: &Buf, levels: Option<f32>) -> u12
         k.u64(e.effect_index as u64);
         k.debug(&e.working_space);
         k.u64(e.working_linear as u64);
+        k.u64(e.float_depth as u64);
         k.debug(&e.shutter);
     }
     k.finish()

crates/gpu/src/shaders/fx_tone.wgsl

@@ -20,6 +20,14 @@ fn fxt_rem360(x: f32) -> f32 {
 }
 
 // Levels (Individual Controls) channel `i` (data: 5 × (ib, iw, g, ob, ow, identity)).
+// color_fx::levels_gamma: unclipped values below 0 mirror the curve.
+fn fxt_gamma(t: f32, g: f32) -> f32 {
+    if (t >= 0.0) {
+        return powz(t, 1.0 / g);
+    }
+    return -powz(-t, 1.0 / g);
+}
+
 fn fxt_lv(i: u32, v: f32, clip_b: bool, clip_w: bool) -> f32 {
     let o = i * 6u;
     if (data[o + 5u] != 0.0) {
@@ -32,7 +40,7 @@ fn fxt_lv(i: u32, v: f32, clip_b: bool, clip_w: bool) -> f32 {
     if (clip_w) {
         t = min(t, 1.0);
     }
-    return data[o + 3u] + (data[o + 4u] - data[o + 3u]) * powz(max(t, 0.0), 1.0 / max(data[o + 2u], 0.01));
+    return data[o + 3u] + (data[o + 4u] - data[o + 3u]) * fxt_gamma(t, max(data[o + 2u], 0.01));
 }
 
 // color_fx::level (data offset o: ib, iw, g, ob, ow, clip black, clip white).
@@ -44,8 +52,7 @@ fn fxt_level(o: u32, v: f32) -> f32 {
     if (data[o + 6u] != 0.0) {
         t = min(t, 1.0);
     }
-    t = powz(max(t, 0.0), 1.0 / data[o + 2u]);
-    return data[o + 3u] + (data[o + 4u] - data[o + 3u]) * t;
+    return data[o + 3u] + (data[o + 4u] - data[o + 3u]) * fxt_gamma(t, data[o + 2u]);
 }
 
 fn fxt_level_ident(o: u32) -> bool {
@@ -177,7 +184,7 @@ fn fxt_point(@builtin(global_invocation_id) gid: vec3<u32>) {
                 let aa = max(a, 0.0);
                 var nc: vec3<f32>;
                 for (var i = 0u; i < 3u; i++) {
-                    nc[i] = fxt_lv(i + 1u, fxt_lv(0u, c[i], cb, cw), cb, cw);
+                    nc[i] = fxt_lv(0u, fxt_lv(i + 1u, c[i], cb, cw), cb, cw);
                 }
                 let na = clamp(clamp(fxt_lv(4u, aa, cb, cw), 0.0, 1.0), 0.0, 1.0);
                 o = vec4<f32>(nc * na, na);

crates/gpu/src/shaders/kernels.wgsl

@@ -703,7 +703,12 @@ fn pointwise(@builtin(global_invocation_id) gid: vec3<u32>) {
                     if (P.u[0].z != 0u) {
                         t = min(t, 1.0);
                     }
-                    t = powz(max(t, 0.0), 1.0 / g);
+                    // color_fx::levels_gamma: unclipped values below 0 mirror the curve.
+                    if (t >= 0.0) {
+                        t = powz(t, 1.0 / g);
+                    } else {
+                        t = -powz(-t, 1.0 / g);
+                    }
                     o[i] = ob + (ow - ob) * t;
                 }
                 px = vec4<f32>(o * a, a);