phosphor-crt 0.1.0

A real-time plotter of waveforms, imitating oscillscope CRTs
Documentation 
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// Screen decay shader - attenuates intermediate texture contents

struct VertexOutput {
    @builtin(position) position: vec4<f32>,
    @location(0) uv: vec2<f32>,
};

@vertex
fn vs_main(@builtin(vertex_index) vertex_index: u32) -> VertexOutput {
    // Generate full-screen triangle:
    // -> uv (0,0), (2,0), (0,2)
    // -> positions (-1,1), (3,1), (-1,-3)
    var out: VertexOutput;
    out.uv = vec2f(f32(vertex_index & 1), f32(vertex_index >> 1)) * 2.0;
    var pos: vec2f = (out.uv * 2.0 - vec2f(1., 1.));
    pos.y = - pos.y;
    out.position = vec4f(pos, 0.0, 1.0);
    return out;
}

@group(0) @binding(0)
var<uniform> viewport: ViewportUniform;

struct ViewportUniform {
    transform: mat3x3<f32>,
    resolution: vec2<u32>,
    beam_radius: f32,
    intensity: f32,  
    gamma: f32,
    decay_per_sample: f32,
    num_samples: u32,
    screen_decay: f32,  // screen decay factor (0.0 = no decay, 1.0 = complete fade)
};

@fragment
fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    // Output black with alpha = (1 - screen_decay)
    // This will multiplicatively blend to attenuate existing pixel values
    let attenuation_factor = exp(-viewport.screen_decay);
    return vec4<f32>(0.0, 0.0, 0.0, attenuation_factor);
}