add dithering

1 files changed, 79 insertions, 11 deletions

diff --git a/src/effects/ntsc.wgsl b/src/effects/ntsc.wgsl
index 8d8d536..ad29c79 100644
--- a/src/effects/ntsc.wgsl
+++ b/src/effects/ntsc.wgsl
@@ -22,7 +22,8 @@ const CROSS_TALK = 0.1;
 const CROSS_Y_INTERFERENCE = 30.;
 const CHROMA_MOD_FREQ = (0.4 * PI);
 
-const C64Colors = array<vec3f, 16>(
+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
@@ -51,7 +52,7 @@ const C64Colors = array<vec3f, 16>(
 // 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) * 0.65 + .5;
+  return uv * (1.0 + scale * strength * (uv * uv).yx) * 0.60 + .50;
 }
 
 fn vignette(uv: vec2f) -> f32 {
@@ -84,7 +85,7 @@ fn yiqa_to_rgba(yiq: vec4f) -> vec4f {
 
 // returns Luma, chroma subcarrier level, phase, transparency
 fn get_luma_chroma_phase_a(uv: vec2f) -> vec4f {
-  let rgba = textureSample(input_texture, input_sampler, uv);
+  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);
 
@@ -123,16 +124,80 @@ 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 = round(bt * 2.) % 2.;
+    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);
@@ -141,7 +206,6 @@ fn randomized_f32(p: vec2f, t: f32) -> f32 {
     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;
-    uv = clamp(uv, vec2f(0.), vec2f(1.));
 
     // luma fringing
     let d = (BLUR_SIZE + y_interf * 100.0) / XSIZE;
@@ -176,17 +240,21 @@ fn randomized_f32(p: vec2f, t: f32) -> f32 {
     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 + 0.18 * sin(PI * uv.y * uniforms.resolution.y / 2.));
-    var col = clamp(scanl * yiqa_to_rgba(signal), vec4f(0.0), vec4f(1.0));
-    let id = round(hash_1f(round(t * .02 + uv.x + YSIZE * uv.y / 8.) + 3. * round(hash_1f(t * 533.) * 24.)) * 16.);
-    let border_col = vec4f(C64Colors[u32(id)], 1.);
-    col = mix(border_col, col, v_strength);
+    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;