path: root/src/effects/ntsc.wgsl

#include "sequence_uniforms"
#include "render/fullscreen_uv_vs"
#include "math/noise"
#include "debug/debug_print"

const PI = 3.14159265;
const TAU = 6.28318530718;

const XSIZE = 54.0 * 8.;
const YSIZE = 33.0 * 8.;
const SCAN_FLICKER = 2.33;
const X_INTERFERENCE = 1.1;
const Y_INTERFERENCE = 0.101;
const LUMA_BRIGHTNESS = 1.1;
const CHROMA_SATURATION = 1.6;
const BLUR_SIZE = 0.2;
const LUMA_BLUR = 1.7;
const CHROMA_BLUR = 0.7;
const CHROMA_SIZE = 6.0;
const SUB_CARRIER = 2.1;
const CROSS_TALK = 0.1;
const CROSS_Y_INTERFERENCE = 30.;
const CHROMA_MOD_FREQ = (0.4 * PI);

const NUM_COLORS : u32 = 16;
const C64Colors = array<vec3f, NUM_COLORS>(
  vec3f(13.0/255.0, 13.0/255.0, 13.0/255.0),       // 0 black
  vec3f(242.0/255.0, 242.0/255.0, 242.0/255.0),    // 1 white
  vec3f(89.0/255.0, 39.0/255.0, 33.0/255.0),      // 2 red
  vec3f(170.0/255.0, 220.0/255.0, 240.0/255.0),    // 3 cyan

  vec3f(101.0/255.0, 27.0/255.0, 109.0/255.0),     // 4 purple
  vec3f(120.0/255.0, 198.0/255.0, 112.0/255.0),    // 5 green
  vec3f(54.0/255.0, 53.0/255.0, 152.0/255.0),      // 6 blue
  vec3f(226.0/255.0, 229.0/255.0, 115.0/255.0),    // 7 yellow

  vec3f(141.0/255.0, 85.0/255.0, 50.0/255.0),      // 8 orange
  vec3f(89.0/255.0, 63.0/255.0, 13.0/255.0),       // 9 brown
  vec3f(189.0/255.0, 110.0/255.0, 115.0/255.0),    // 10 pink
  vec3f(80.0/255.0, 80.0/255.0, 80.0/255.0),       // 11 dark gray

  vec3f(124.0/255.0, 124.0/255.0, 124.0/255.0),    // 12 gray
  vec3f(165.0/255.0, 242.0/255.0, 156.0/255.0),    // 13 bright green
  vec3f(114.0/255.0, 111.0/255.0, 224.0/255.0),    // 14 light blue
  vec3f(128.0/255.0, 128.0/255.0, 128.0/255.0)     // 15 middle gray
);

@group(0) @binding(0) var input_sampler: sampler;
@group(0) @binding(1) var input_texture: texture_2d<f32>;
@group(0) @binding(2) var<uniform> uniforms: UniformsSequenceParams;

// Barrel (fisheye) distortion: strength > 0 = barrel, < 0 = pincushion
fn fisheye(uv: vec2f, scale: f32) -> vec2f {
  const strength = vec2f(0.1, 0.24);
  return uv * (1.0 + scale * strength * (uv * uv).yx) * 0.60 + .50;
}

fn vignette(uv: vec2f) -> f32 {
  const vignetteRounding = 160.0;
  const vignetteSmoothness = 0.7;
  let uv2 = 2.0 * uv - 1.0;
  let amount = 1.0 - sqrt(pow(abs(uv2.x), vignetteRounding) + pow(abs(uv2.y), vignetteRounding));
  return smoothstep(0., vignetteSmoothness, amount);
}

fn rgba_to_yiqa(rgba: vec4f) -> vec4f {
  const rgb_yiq_mat = mat4x4f(
    0.299,  0.596,  0.211, 0.,
    0.587, -0.274, -0.523, 0.,
    0.114, -0.322,  0.312, 0.,
       0.,     0.,     0., 1.,
  );
  return rgb_yiq_mat * rgba;
}

fn yiqa_to_rgba(yiq: vec4f) -> vec4f {
  const yiq_rgb_mat = mat4x4f(
    1.000,  1.000,   1.000, 0.,
    0.956, -0.272,  -1.106, 0.,
    0.621, -0.647,   1.703, 0.,
       0.,     0.,      0., 1.,
  );
  return yiq_rgb_mat * yiq;
}

// returns Luma, chroma subcarrier level, phase, transparency
fn get_luma_chroma_phase_a(uv: vec2f) -> vec4f {
  let rgba = Dither(textureSample(input_texture, input_sampler, uv), uv);
  let yiq = rgba_to_yiqa(textureSample(input_texture, input_sampler, uv));
  let chroma_level = length(yiq.yz);

  // 22.5 degrees phase shift between lines
//  let mscanl = (uv.y * uniforms.resolution.y / 4.) % 2.0;
  let mscanl = (uv.y * YSIZE) % 2.0;
  let phase = atan2(yiq.y, yiq.z) - 0.3926991 + mscanl * 0.19634954;
  return vec4f(yiq.x, chroma_level, phase / TAU, yiq.a);
}

fn get_value(uv: vec2f, off: f32, yscale: f32) -> vec4f {
  return get_luma_chroma_phase_a(uv + off * vec2f(1., yscale));
}

fn peak(y: f32, ypos: f32, scale: f32) -> f32 {
  return clamp((y - 1.) * scale * log(abs(y - ypos)), 0.0, 1.0);
}

// 12-taps horizontal filtering
const luma_filter = array<f32, 2 * 12 + 1>(
   0.0105, 0.0134, 0.0057,-0.0242,-0.0824,
  -0.1562,-0.2078,-0.1850,-0.0546, 0.1626,
   0.3852, 0.5095, 0.5163, 0.4678, 0.2844,
   0.0515,-0.1308,-0.2082,-0.1891,-0.1206,
  -0.0511,-0.0065, 0.0114, 0.0127, 0.008
);
const chroma_filter = array<f32, 2 * 12 + 1>(
  0.001,  0.0010, 0.0001, 0.0002, -0.0003,
  0.0062, 0.0120,-0.0079, 0.0978,  0.1059,
 -0.0394, 0.2732, 0.2941, 0.1529, -0.021,
  0.1347, 0.0415,-0.0032, 0.0115,  0.002,
 -0.0001, 0.0002, 0.001,  0.001,   0.001
);

fn randomized_f32(p: vec2f, t: f32) -> f32 {
  return hash_2f_alt(vec2f(p * 0.152 + t * 1500. + 50.0));
}

const BAYER_8X8 = array<u32, 64>(
     0, 32,  8, 40,  2, 34, 10, 42,
    48, 16, 56, 24, 50, 18, 58, 26,
    12, 44,  4, 36, 14, 46,  6, 38,
    60, 28, 52, 20, 62, 30, 54, 22,
     3, 35, 11, 43,  1, 33,  9, 41,
    51, 19, 59, 27, 49, 17, 57, 25,
    15, 47,  7, 39, 13, 45,  5, 37,
    63, 31, 55, 23, 61, 29, 53, 21
);

const DistanceParam = 0.65;
fn colorDistance(color: vec4f, c1: vec4f, c2: vec4f, frac: f32) -> f32 {
  return mix(distance(color, mix(c1, c2, frac)),
             distance(color, c1) + distance(color, c2),
             0.5 * DistanceParam * DistanceParam);
}

fn Dither(col: vec4f, uv: vec2f) -> vec4f {
  let ix = u32(floor(uv.x * XSIZE / 2.)) % 8;
  let iy = u32(floor(uv.y * YSIZE / 2.)) % 8;
  let thresh = f32(BAYER_8X8[ix + 8 * iy]) / 64.;

  var color = min(col, vec4f(1.));
  color *= color;  // ~gamma

  var c1 = vec4f(0.);
  var c2 = vec4f(0.);
  var frac = 0.0;
  var best = 1.e5;

  for (var i = 0u; i < NUM_COLORS; i += 1u) {
    var p1 = vec4f(C64Colors[i], 1.);
    p1 *= p1;
    for (var j = i + 1u; j < NUM_COLORS; j += 1u) {
      var p2 = vec4f(C64Colors[j], 1.);
      p2 *= p2;

      // min-L2 optim
      let dc = p1 - p2;
      var a = dot(dc, p1 - color) / dot(dc, dc);
      a = clamp(a, 0., 1.);
      let dist = colorDistance(color, p1, p2, a);
      if (dist < best) {
        best = dist;
        c1 = p1;
        c2 = p2;
        frac = a;
      }
    }
  }
  color = mix(c1, c2, f32(frac > thresh));
//  color = mix(c1, c2, frac);
  return sqrt(color);
}

fn get_border_col(uv: vec2f) -> vec4f {
  let t = uniforms.beat_time;
  let offset = uv.x + YSIZE * uv.y / 8.;
  let phase = 3. * round(hash_1f(t * 533.) * 24.);
  let id = round(hash_1f(round(sin(t * 1.6) + offset + phase)) * 8.);
  let border_col = vec4f(C64Colors[u32(id)], 1.);
  return border_col;
}

@fragment fn fs_main(in: VertexOutput) -> @location(0) vec4f {
    let t = uniforms.time;
    let bt = uniforms.beat_phase;

    // Fisheye/barrel distortion
    var uv = fisheye(in.st, 0.18);
    let mframe = sin(bt * 32.) * 1.2;
    uv.y += mframe * SCAN_FLICKER / uniforms.resolution.y;  // flicker at target resolution

    // interference
    let cur_line = round(uv.y * YSIZE);
    var r = randomized_f32(vec2f(0.0, cur_line), uniforms.time);
    if (r > 0.995) { r *= 3.0; }

    let x_interf = X_INTERFERENCE * r / XSIZE;
    let y_interf = Y_INTERFERENCE * r * peak(uv.y, 0.2, 0.03);
    uv.x += x_interf - y_interf;

    // luma fringing
    let d = (BLUR_SIZE + y_interf * 100.0) / XSIZE;
    var lc_signal = vec4f(0.0);
    for (var i = 0; i < 25; i += 1) {
      let offset = f32(i) - 12.0;
      let suml = luma_filter[i] * get_value(uv, offset * d, 0.67);
      let sumc = chroma_filter[i] * get_value(uv, offset * d * CHROMA_SIZE, 0.67);
      lc_signal += vec4f(suml.x, sumc.y, sumc.z, suml.a);
    }
    let base = get_luma_chroma_phase_a(uv);
    var signal = mix(base, lc_signal, vec4f(LUMA_BLUR, CHROMA_BLUR, CHROMA_BLUR, 1.));

    // luma / chroma saturation
    let lchroma = signal.y * CHROMA_SATURATION;
    let phase = signal.z * TAU;

    signal.x *= LUMA_BRIGHTNESS;
    signal.y = lchroma * sin(phase);
    signal.z = lchroma * cos(phase);
    // Slight NTSC warm tint (boost red/green, attenuate blue)
    signal *= vec4f(1.04, 1.01, .94, 1.);

    // color subcarrier signal, crosstalk
    let chroma_phase = t * 60.0 * PI * 0.6667;
    let mod_phase = chroma_phase + dot(uv, vec2f(1.0, 0.1)) * CHROMA_MOD_FREQ * XSIZE * 2.0;
    let scarrier = SUB_CARRIER * lchroma;
    let i_mod = cos(mod_phase);
    let q_mod = sin(mod_phase);

    signal.x *= 1.0 + CROSS_TALK * scarrier * q_mod - y_interf * CROSS_Y_INTERFERENCE;
    signal.y *= 1.0 + scarrier * i_mod;
    signal.z *= 1.0 + scarrier * q_mod;

    var col = yiqa_to_rgba(signal);
    col = Dither(col, uv);

    let border_col = get_border_col(uv);

    let v_strength = vignette(uv);
    let scanl = 0.82 + 0.5 * sin(PI * uv.y * uniforms.resolution.y / 2.);
    col = scanl * mix(border_col, col, v_strength);
    col = clamp(col, vec4f(0., 0., 0., 1.), vec4f(1.0));

    // Black outside screen edges
    if (uv.x <= 0.0 || uv.x >= 1.0 || uv.y <= 0.0 || uv.y >= 1.0) {
	// discard;
    }

    col = debug_f32(col, in.position.xy / 2., vec2f(100., 75.), uniforms.beat_time);
    col = debug_str(col, in.position.xy / 2., vec2f(100., 150.), vec4u(0x48656C6Cu, 0x6F000000u, 0u, 0u), 5u);
    return col;
}