1 files changed, 98 insertions, 0 deletions
diff --git a/src/effects/fade_effect.cc b/src/effects/fade_effect.cc
new file mode 100644
index 0000000..fd2af69
--- /dev/null
+++ b/src/effects/fade_effect.cc
@@ -0,0 +1,98 @@
+// This file is part of the 64k demo project.
+// It implements the FadeEffect - fades to/from black based on time.
+
+#include "effects/fade_effect.h"
+#include "gpu/post_process_helper.h"
+#include <cmath>
+
+struct FadeParams {
+  float fade_amount;
+  float _pad[3];
+};
+static_assert(sizeof(FadeParams) == 16, "FadeParams must be 16 bytes for WGSL alignment");
+
+FadeEffect::FadeEffect(const GpuContext& ctx) : PostProcessEffect(ctx) {
+  const char* shader_code = R"(
+    struct VertexOutput {
+      @builtin(position) position: vec4<f32>,
+      @location(0) uv: vec2<f32>,
+    };
+
+    struct CommonUniforms {
+      resolution: vec2<f32>,
+      _pad0: f32,
+      _pad1: f32,
+      aspect_ratio: f32,
+      time: f32,
+      beat: f32,
+      audio_intensity: f32,
+    };
+
+    struct FadeParams {
+      fade_amount: 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: CommonUniforms;
+    @group(0) @binding(3) var<uniform> params: FadeParams;
+
+    @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);
+      // Fade to black: 0.0 = black, 1.0 = full color
+      return vec4<f32>(color.rgb * params.fade_amount, color.a);
+    }
+  )";
+
+  pipeline_ =
+      create_post_process_pipeline(ctx_.device, ctx_.format, shader_code);
+  params_buffer_ = gpu_create_buffer(
+      ctx_.device, 16, WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
+}
+
+void FadeEffect::update_bind_group(WGPUTextureView input_view) {
+  pp_update_bind_group(ctx_.device, pipeline_, &bind_group_, input_view,
+                       uniforms_.get(), params_buffer_);
+}
+
+void FadeEffect::render(WGPURenderPassEncoder pass,
+                        const CommonPostProcessUniforms& uniforms) {
+  uniforms_.update(ctx_.queue, uniforms);
+
+  // Example fade pattern: fade in at start, fade out at end
+  // Customize this based on your needs
+  float fade_amount = 1.0f;
+  if (uniforms.time < 2.0f) {
+    // Fade in from black over first 2 seconds
+    fade_amount = uniforms.time / 2.0f;
+  } else if (uniforms.time > 36.0f) {
+    // Fade out to black after 36 seconds
+    fade_amount = 1.0f - ((uniforms.time - 36.0f) / 4.0f);
+    fade_amount = fmaxf(fade_amount, 0.0f);
+  }
+
+  FadeParams params = {fade_amount, {0.0f, 0.0f, 0.0f}};
+  wgpuQueueWriteBuffer(ctx_.queue, params_buffer_.buffer, 0, &params,
+                       sizeof(params));
+
+  wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
+  wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
+  wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
+}