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// 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);
}
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