From 4a2ca9115bf71e926c554f21874de678fa49a005 Mon Sep 17 00:00:00 2001
From: Brandon Thomas <echelon@gmail.com>
Date: Sat, 3 Oct 2026 23:59:22 -0400
Subject: [PATCH] M13.23: Shatter wireframe views and Foam's texture / map
 extras fall back via gpu_supported (no readback attempt)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 crates/effects/src/catalog.rs  | 13 +++++++++++++
 crates/effects/src/sim2.rs     |  8 +-------
 crates/gpu/src/tests_fx_sim.rs |  8 ++++++++
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/crates/effects/src/catalog.rs b/crates/effects/src/catalog.rs
index ca580b9d..1e1b4bc2 100644
--- a/crates/effects/src/catalog.rs
+++ b/crates/effects/src/catalog.rs
@@ -97,6 +97,19 @@ pub fn gpu_supported(id: &str, ctx: &crate::EffectCtx) -> bool {
     match id {
         "ec.generate.cellpattern" if (6..=10).contains(&ctx.params.e("cellPattern")) => return false,
         "ec.distort.turbulentdisplace" if ctx.params.e("pinning") >= 8 => return false,
+        // Shatter's wireframe views; Foam's User Defined texture, Environment Map and flow-map
+        // preview (the GPU draws the rendered pieces and the sprite bubbles only).
+        "ec.sim.shatter" if ctx.params.e("view") != 0 => return false,
+        "ec.sim.foam" => {
+            let set = |id: &str| matches!(ctx.params.get(id), Some(effectcraft_keyframe::Value::Layer(Some(_))));
+            let view = ctx.params.e("view");
+            if (view == 2 && ctx.params.e("rendering/bubbleTexture") == 5)
+                || (view == 2 && ctx.params.f("rendering/reflectionStrength") > 0.0 && set("rendering/environmentMap"))
+                || (view == 1 && set("flowMap/flowMap"))
+            {
+                return false;
+            }
+        }
         // Fisheye / Twist (a crease at the unit circle) bent past 50 % or with Horizontal /
         // Vertical Distortion: Newton's inverse wanders chaotically before converging near the
         // fold, so f32 lands on other pixels than the CPU's f64.
diff --git a/crates/effects/src/sim2.rs b/crates/effects/src/sim2.rs
index d682a310..98634b0f 100644
--- a/crates/effects/src/sim2.rs
+++ b/crates/effects/src/sim2.rs
@@ -1525,13 +1525,7 @@ fn foam(ctx: &EffectCtx, b: Buf) -> Buf {
 /// Foam's bubbles as sprites, `None` when it draws more than sprites (a User Defined bubble
 /// texture, an Environment Map reflection or the Draft + Flow Map view's flow map).
 pub(crate) fn foam_plan(ctx: &EffectCtx, b: &Buf) -> Option<crate::sim::SpritePlan> {
-    let pr = ctx.params;
-    let set = |id: &str| matches!(pr.get(id), Some(Value::Layer(Some(_))));
-    let view = pr.e("view");
-    if (view == 2 && pr.e("rendering/bubbleTexture") == 5)
-        || (view == 2 && pr.f("rendering/reflectionStrength") > 0.0 && set("rendering/environmentMap"))
-        || (view == 1 && set("flowMap/flowMap"))
-    {
+    if !crate::catalog::gpu_supported("ec.sim.foam", ctx) {
         return None;
     }
     foam_impl(ctx, b, true).err()
diff --git a/crates/gpu/src/tests_fx_sim.rs b/crates/gpu/src/tests_fx_sim.rs
index 55dc62c4..d6977779 100644
--- a/crates/gpu/src/tests_fx_sim.rs
+++ b/crates/gpu/src/tests_fx_sim.rs
@@ -152,3 +152,11 @@ fn caustics() {
     );
     let _ = (c(0.0, 0.0, 0.0), on());
 }
+
+#[test]
+fn cpu_only_views_fall_back() {
+    // Shatter's wireframe views and Foam's User Defined texture render on the CPU; composited
+    // frames still match.
+    composited("ec.sim.shatter", &[], 1.0, 0.0);
+    composited("ec.sim.foam", &[("view", e(2)), ("rendering/bubbleTexture", e(5)), ("rendering/bubbleTextureLayer", Value::Layer(Some(0)))], 1.0, 0.0);
+}