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// This file is part of the 64k demo project.
// It implements the FlashEffect - brief flash on beat hits.
// Now supports parameterized color with per-frame animation.
#include "gpu/effects/flash_effect.h"
#include "gpu/effects/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,
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);
uniforms_.init(ctx_.device);
}
void FlashEffect::update_bind_group(WGPUTextureView input_view) {
pp_update_bind_group(ctx_.device, pipeline_, &bind_group_, input_view,
uniforms_.get());
}
void FlashEffect::render(WGPURenderPassEncoder pass, float time, float beat,
float intensity, float aspect_ratio) {
(void)aspect_ratio;
// Trigger flash based on configured threshold
if (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(time * 0.5f));
const float g = params_.color[1] * (0.5f + 0.5f * cosf(time * 0.7f));
const float b = params_.color[2] * (1.0f + 0.3f * beat);
// Update uniforms with computed (animated) values
const FlashUniforms u = {
.flash_intensity = flash_intensity_,
.intensity = intensity,
._pad1 = {0.0f, 0.0f}, // Padding for vec3 alignment
.color = {r, g, b}, // Time-dependent, computed every frame
._pad2 = 0.0f};
uniforms_.update(ctx_.queue, u);
wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
}
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