3 files changed, 71 insertions, 5 deletions

diff --git a/src/gpu/effect.cc b/src/gpu/effect.cc
index b729321..117ede2 100644
--- a/src/gpu/effect.cc
+++ b/src/gpu/effect.cc
@@ -1,11 +1,64 @@
 // Effect implementation
 
 #include "gpu/effect.h"
+#include "gpu/gpu.h"
+#include "gpu/sequence.h"
 #include "util/fatal_error.h"
 
 Effect::Effect(const GpuContext& ctx, const std::vector<std::string>& inputs,
-               const std::vector<std::string>& outputs)
-    : ctx_(ctx), input_nodes_(inputs), output_nodes_(outputs) {
+               const std::vector<std::string>& outputs, float start_time,
+               float end_time)
+    : ctx_(ctx), input_nodes_(inputs), output_nodes_(outputs),
+      start_time_(start_time), end_time_(end_time) {
   FATAL_CHECK(!inputs.empty(), "Effect must have at least one input\n");
   FATAL_CHECK(!outputs.empty(), "Effect must have at least one output\n");
+  FATAL_CHECK(start_time <= end_time, "Invalid time range: %f > %f\n",
+              start_time, end_time);
+}
+
+void Effect::dispatch_render(WGPUCommandEncoder encoder,
+                              const UniformsSequenceParams& params,
+                              NodeRegistry& nodes) {
+  // Check if effect is active at current time
+  const bool active =
+      (params.time >= start_time_ && params.time < end_time_);
+
+  // Auto-passthrough for 1:1 input/output effects outside active range
+  if (!active && input_nodes_.size() == 1 && output_nodes_.size() == 1) {
+    blit_input_to_output(encoder, nodes);
+  } else if (active) {
+    render(encoder, params, nodes);
+  }
+  // Multi-output effects: output undefined when inactive (validated at compile time)
+}
+
+void Effect::blit_input_to_output(WGPUCommandEncoder encoder,
+                                   NodeRegistry& nodes) {
+  HEADLESS_RETURN_IF_NULL(encoder);
+
+  WGPUTexture src = nodes.get_texture(input_nodes_[0]);
+  WGPUTexture dst = nodes.get_texture(output_nodes_[0]);
+
+  // Skip passthrough if textures are external (source/sink) or invalid
+  if (!src || !dst) {
+    return;
+  }
+
+#if defined(DEMO_CROSS_COMPILE_WIN32)
+  WGPUImageCopyTexture src_copy = {
+      .texture = src, .mipLevel = 0, .origin = {0, 0, 0}};
+  WGPUImageCopyTexture dst_copy = {
+      .texture = dst, .mipLevel = 0, .origin = {0, 0, 0}};
+#else
+  WGPUTexelCopyTextureInfo src_copy = {
+      .texture = src, .mipLevel = 0, .origin = {0, 0, 0}};
+  WGPUTexelCopyTextureInfo dst_copy = {
+      .texture = dst, .mipLevel = 0, .origin = {0, 0, 0}};
+#endif
+
+  WGPUExtent3D extent = {static_cast<unsigned int>(width_),
+                         static_cast<unsigned int>(height_), 1};
+
+  wgpuCommandEncoderCopyTextureToTexture(encoder, &src_copy, &dst_copy,
+                                         &extent);
 }
diff --git a/src/gpu/effect.h b/src/gpu/effect.h
index d40e750..0d7e35e 100644
--- a/src/gpu/effect.h
+++ b/src/gpu/effect.h
@@ -14,7 +14,8 @@ class NodeRegistry;
 class Effect {
  public:
   Effect(const GpuContext& ctx, const std::vector<std::string>& inputs,
-         const std::vector<std::string>& outputs);
+         const std::vector<std::string>& outputs, float start_time,
+         float end_time);
   virtual ~Effect() = default;
 
   // Optional: Declare temporary nodes (e.g., multi-pass intermediate buffers)
@@ -22,7 +23,12 @@ class Effect {
     (void)registry;
   }
 
-  // Render effect (multi-input/multi-output)
+  // Dispatch render with automatic passthrough outside [start, end]
+  void dispatch_render(WGPUCommandEncoder encoder,
+                       const UniformsSequenceParams& params,
+                       NodeRegistry& nodes);
+
+  // Render effect (multi-input/multi-output) - override in derived classes
   virtual void render(WGPUCommandEncoder encoder,
                       const UniformsSequenceParams& params,
                       NodeRegistry& nodes) = 0;
@@ -46,5 +52,12 @@ class Effect {
   std::vector<std::string> output_nodes_;
   int width_ = 1280;
   int height_ = 720;
+
+ private:
+  float start_time_;
+  float end_time_;
+
+  // Auto-passthrough helper for 1:1 input/output effects
+  void blit_input_to_output(WGPUCommandEncoder encoder, NodeRegistry& nodes);
 };
 #endif // EFFECT_H
diff --git a/src/gpu/sequence.cc b/src/gpu/sequence.cc
index 5348992..d2f99bc 100644
--- a/src/gpu/sequence.cc
+++ b/src/gpu/sequence.cc
@@ -240,7 +240,7 @@ void Sequence::postprocess(WGPUCommandEncoder encoder) {
 void Sequence::render_effects(WGPUCommandEncoder encoder) {
   // Execute DAG in topological order (pre-sorted by compiler)
   for (const auto& dag_node : effect_dag_) {
-    dag_node.effect->render(encoder, params_, nodes_);
+    dag_node.effect->dispatch_render(encoder, params_, nodes_);
   }
 }