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// This file is part of the 64k demo project.
// It implements theme modulation (bright/dark alternation).
#include "gpu/effects/theme_modulation_effect.h"
#include "gpu/effects/post_process_helper.h"
#include "gpu/effects/shaders.h"
#include <cmath>
ThemeModulationEffect::ThemeModulationEffect(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 {
theme_brightness: 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;
// Large triangle trick for fullscreen coverage
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);
// Apply theme brightness modulation
return vec4<f32>(color.rgb * uniforms.theme_brightness, color.a);
}
)";
pipeline_ = create_post_process_pipeline(device, format, shader_code);
// Create uniform buffer (4 floats: brightness + padding)
uniforms_ = gpu_create_buffer(device, 16, WGPUBufferUsage_Uniform | WGPUBufferUsage_CopyDst);
}
void ThemeModulationEffect::update_bind_group(WGPUTextureView input_view) {
pp_update_bind_group(device_, pipeline_, &bind_group_, input_view, uniforms_);
}
void ThemeModulationEffect::render(WGPURenderPassEncoder pass, float time,
float beat, float intensity,
float aspect_ratio) {
(void)beat;
(void)intensity;
(void)aspect_ratio;
// Alternate between bright and dark every 4 seconds (2 pattern changes)
// Music patterns change every 2 seconds at 120 BPM
float cycle_time = fmodf(time, 8.0f); // 8 second cycle (4 patterns)
bool is_dark_section = (cycle_time >= 4.0f); // Dark for second half
// Smooth transition between themes using a sine wave
float transition = (std::sin(time * 3.14159f / 4.0f) + 1.0f) * 0.5f; // 0.0 to 1.0
float bright_value = 1.0f;
float dark_value = 0.35f;
float theme_brightness = bright_value + (dark_value - bright_value) * transition;
// Update uniform buffer
float uniforms[4] = {theme_brightness, 0.0f, 0.0f, 0.0f};
wgpuQueueWriteBuffer(queue_, uniforms_.buffer, 0, uniforms, sizeof(uniforms));
// Render
wgpuRenderPassEncoderSetPipeline(pass, pipeline_);
wgpuRenderPassEncoderSetBindGroup(pass, 0, bind_group_, 0, nullptr);
wgpuRenderPassEncoderDraw(pass, 3, 1, 0, 0);
}
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