accumulator blur

compositor.cm

@@ -176,6 +176,7 @@ function compile_group(node, ctx, target, target_size, parent_target, parent_siz
   // Apply effects if any
   if (node.effects) {
     for (var effect of node.effects) {
+      effect._node_id = node.name || `node_${ctx.target_counter}`
       target = compile_effect(effect, ctx, target, target_size)
     }
   }
@@ -308,6 +309,10 @@ function compile_effect(effect, ctx, input_target, target_size) {
     return compile_blur_effect(effect, ctx, input_target, target_size)
   }
   
+  if (effect_type == 'accumulator') {
+    return compile_accumulator_effect(effect, ctx, input_target, target_size)
+  }
+  
   return input_target
 }
 
@@ -444,6 +449,46 @@ function compile_blur_effect(effect, ctx, input_target, target_size) {
   return src
 }
 
+// Compile accumulator effect (motion blur)
+function compile_accumulator_effect(effect, ctx, input_target, target_size) {
+  var decay = effect.decay != null ? effect.decay : 0.9
+  var node_id = effect._node_id || ctx.target_counter++
+  
+  // Create persistent targets for ping-ponging
+  // We use stable keys based on node_id to ensure they persist across frames in the backend
+  var accum_prev_key = `accum_prev_${node_id}`
+  var accum_curr_key = `accum_curr_${node_id}`
+  
+  var accum_prev = {type: 'target', key: accum_prev_key, width: target_size.width, height: target_size.height, persistent: true}
+  var accum_curr = {type: 'target', key: accum_curr_key, width: target_size.width, height: target_size.height, persistent: true}
+  
+  // Register them in the plan so the backend knows to create them
+  ctx.targets[accum_prev_key] = {width: target_size.width, height: target_size.height, name: accum_prev_key, persistent: true}
+  ctx.targets[accum_curr_key] = {width: target_size.width, height: target_size.height, name: accum_curr_key, persistent: true}
+  
+  // Accumulation pass: curr = max(input, prev * decay)
+  ctx.passes.push({
+    type: 'shader_pass',
+    shader: 'accumulator',
+    input: input_target,
+    extra_inputs: [accum_prev],
+    output: accum_curr,
+    uniforms: {decay: decay}
+  })
+  
+  // Feedback pass: copy curr back to prev for next frame
+  ctx.passes.push({
+    type: 'composite',
+    source: accum_curr,
+    dest: accum_prev,
+    source_size: target_size,
+    dest_size: target_size,
+    presentation: 'disabled'
+  })
+  
+  return accum_curr
+}
+
 // ========================================================================
 // HELPERS
 // ========================================================================
@@ -600,11 +645,18 @@ function execute_pass(pass, renderers, backend, resolve_target) {
     case 'shader_pass':
       var input = resolve_target(pass.input)
       var output = resolve_target(pass.output)
+      var extra_inputs = []
+      if (pass.extra_inputs) {
+        for (var t of pass.extra_inputs) {
+          extra_inputs.push(resolve_target(t))
+        }
+      }
       commands.push({
         cmd: 'shader_pass',
         shader: pass.shader,
         input: input,
         output: output,
+        extra_inputs: extra_inputs,
         uniforms: pass.uniforms
       })
       break