1 files changed, 94 insertions, 0 deletions
diff --git a/src/effects/flash_effect.cc b/src/effects/flash_effect.cc
new file mode 100644
index 0000000..235412d
--- /dev/null
+++ b/src/effects/flash_effect.cc
@@ -0,0 +1,94 @@
+// This file is part of the 64k demo project.
+// It implements the FlashEffect - brief flash on u.beat hits.
+// Now supports parameterized color with per-frame animation.
+
+#include "effects/flash_effect.h"
+#include "gpu/post_process_helper.h"
+#include <cmath>
+
+// Backward compatibility constructor (delegates to parameterized constructor)
+FlashEffect::FlashEffect(const GpuContext& ctx)
+    : FlashEffect(ctx, FlashEffectParams{}) {
+}
+
+// Parameterized constructor
+FlashEffect::FlashEffect(const GpuContext& ctx, const FlashEffectParams& params)
+    : PostProcessEffect(ctx), params_(params) {
+  const char* shader_code = R"(
+    struct VertexOutput {
+      @builtin(position) position: vec4<f32>,
+      @location(0) uv: vec2<f32>,
+    };
+
+    struct Uniforms {
+      flash_intensity: f32,
+      audio_intensity: f32,
+      flash_color: vec3<f32>,  // Parameterized color
+      _pad: 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);
+      // Use parameterized flash color instead of hardcoded white
+      var flashed = mix(color.rgb, uniforms.flash_color, uniforms.flash_intensity);
+      return vec4<f32>(flashed, color.a);
+    }
+  )";
+
+  pipeline_ =
+      create_post_process_pipeline(ctx_.device, ctx_.format, shader_code);
+  flash_uniforms_.init(ctx_.device);
+}
+
+void FlashEffect::update_bind_group(WGPUTextureView input_view) {
+  pp_update_bind_group(ctx_.device, pipeline_, &bind_group_, input_view,
+                       flash_uniforms_.get(), {});
+}
+
+void FlashEffect::render(WGPURenderPassEncoder pass,
+                         const CommonPostProcessUniforms& uniforms) {
+  // Trigger flash based on configured threshold
+  if (uniforms.audio_intensity > params_.trigger_threshold && flash_intensity_ < 0.2f) {
+    flash_intensity_ = 0.8f; // Trigger flash
+  }
+
+  // Decay based on configured rate
+  flash_intensity_ *= params_.decay_rate;
+
+  // *** PER-FRAME PARAMETER COMPUTATION ***
+  // Animate color based on time and beat
+  const float r = params_.color[0] * (0.5f + 0.5f * sinf(uniforms.time * 0.5f));
+  const float g = params_.color[1] * (0.5f + 0.5f * cosf(uniforms.time * 0.7f));
+  const float b = params_.color[2] * (1.0f + 0.3f * uniforms.beat_phase);
+
+  // Update uniforms with computed (animated) values
+  const FlashUniforms u = {
+      .flash_intensity = flash_intensity_,
+      .intensity = uniforms.audio_intensity,
+      ._pad1 = {0.0f, 0.0f}, // Padding for vec3 alignment
+      .color = {r, g, b},    // Time-dependent, computed every frame
+      ._pad2 = 0.0f};
+  flash_uniforms_.update(ctx_.queue, u);
+
+  wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
+  wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
+  wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
+}