1 files changed, 79 insertions, 0 deletions
diff --git a/src/gpu/effects/flash_effect.cc b/src/gpu/effects/flash_effect.cc
new file mode 100644
index 0000000..de7be62
--- /dev/null
+++ b/src/gpu/effects/flash_effect.cc
@@ -0,0 +1,79 @@
+// This file is part of the 64k demo project.
+// It implements the FlashEffect - brief white flash on beat hits.
+
+#include "gpu/effects/flash_effect.h"
+#include "gpu/effects/post_process_helper.h"
+#include <cmath>
+
+FlashEffect::FlashEffect(WGPUDevice device, WGPUQueue queue,
+                         WGPUTextureFormat format)
+    : PostProcessEffect(device, queue) {
+  const char* shader_code = R"(
+    struct VertexOutput {
+      @builtin(position) position: vec4<f32>,
+      @location(0) uv: vec2<f32>,
+    };
+
+    struct Uniforms {
+      flash_intensity: f32,
+      _pad0: f32,
+      _pad1: f32,
+      _pad2: f32,
+    };
+
+    @group(0) @binding(0) var inputSampler: sampler;
+    @group(0) @binding(1) var inputTexture: texture_2d<f32>;
+    @group(0) @binding(2) var<uniform> uniforms: Uniforms;
+
+    @vertex
+    fn vs_main(@builtin(vertex_index) vertexIndex: u32) -> VertexOutput {
+      var output: VertexOutput;
+      var pos = array<vec2<f32>, 3>(
+        vec2<f32>(-1.0, -1.0),
+        vec2<f32>(3.0, -1.0),
+        vec2<f32>(-1.0, 3.0)
+      );
+      output.position = vec4<f32>(pos[vertexIndex], 0.0, 1.0);
+      output.uv = pos[vertexIndex] * 0.5 + 0.5;
+      return output;
+    }
+
+    @fragment
+    fn fs_main(input: VertexOutput) -> @location(0) vec4<f32> {
+      let color = textureSample(inputTexture, inputSampler, input.uv);
+      // Add white flash: blend towards white based on flash intensity
+      let white = vec3<f32>(1.0, 1.0, 1.0);
+      let flashed = mix(color.rgb, white, uniforms.flash_intensity);
+      return vec4<f32>(flashed, color.a);
+    }
+  )";
+
+  pipeline_ = create_post_process_pipeline(device, format, shader_code);
+  uniforms_ = gpu_create_buffer(device, 16, WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
+}
+
+void FlashEffect::update_bind_group(WGPUTextureView input_view) {
+  pp_update_bind_group(device_, pipeline_, &bind_group_, input_view, uniforms_);
+}
+
+void FlashEffect::render(WGPURenderPassEncoder pass, float time,
+                         float beat, float intensity, float aspect_ratio) {
+  (void)time;
+  (void)beat;
+  (void)aspect_ratio;
+
+  // Trigger flash on strong beat hits
+  if (intensity > 0.7f && flash_intensity_ < 0.2f) {
+    flash_intensity_ = 0.8f;  // Trigger flash
+  }
+
+  // Exponential decay
+  flash_intensity_ *= 0.85f;
+
+  float uniforms[4] = {flash_intensity_, 0.0f, 0.0f, 0.0f};
+  wgpuQueueWriteBuffer(queue_, uniforms_.buffer, 0, uniforms, sizeof(uniforms));
+
+  wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
+  wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
+  wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
+}