refactor: mv get_border_col() to color_c64.wgsl as get_border_c64()

2 files changed, 13 insertions, 12 deletions

diff --git a/src/effects/ntsc.wgsl b/src/effects/ntsc.wgsl
index 9901c88..a701a25 100644
--- a/src/effects/ntsc.wgsl
+++ b/src/effects/ntsc.wgsl
@@ -78,14 +78,6 @@ fn randomized_f32(p: vec2f, t: f32) -> f32 {
 }
 
 
-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;
@@ -141,7 +133,7 @@ fn get_border_col(uv: vec2f) -> vec4f {
     var col = yiqa_to_rgba(signal);
     col = Dither(col, uv, XSIZE, YSIZE);
 
-    let border_col = get_border_col(uv);
+    let border_col = get_border_c64(uv, uniforms.beat_time, YSIZE);
 
     let v_strength = vignette(uv);
     let scanl = 0.82 + 0.5 * sin(PI * uv.y * uniforms.resolution.y / 2.);
diff --git a/src/shaders/math/color_c64.wgsl b/src/shaders/math/color_c64.wgsl
index ef8f073..e1b142e 100644
--- a/src/shaders/math/color_c64.wgsl
+++ b/src/shaders/math/color_c64.wgsl
@@ -1,6 +1,6 @@
-// C64 palette and ordered-dither quantization.
-// Provides Dither() to snap any RGBA color to the nearest C64 color pair
-// via 8x8 Bayer threshold, suitable for NTSC and retro post-process effects.
+// C64 palette, ordered-dither quantization, and border color animation.
+// Provides Dither() and get_border_c64() for NTSC and retro post-process effects.
+#include "math/noise"
 
 const NUM_COLORS : u32 = 16;
 const C64Colors = array<vec3f, NUM_COLORS>(
@@ -81,3 +81,12 @@ fn Dither(col: vec4f, uv: vec2f, xsize: f32, ysize: f32) -> vec4f {
   color = mix(c1, c2, f32(frac > thresh));
   return sqrt(color);
 }
+
+// Animated C64 border color: cycles through palette driven by beat_time.
+// ysize: virtual scanline count (e.g. 33.*8.), matching the pixel grid.
+fn get_border_c64(uv: vec2f, beat_time: f32, ysize: f32) -> vec4f {
+  let offset = uv.x + ysize * uv.y / 8.;
+  let phase = 3. * round(hash_1f(beat_time * 533.) * 24.);
+  let id = round(hash_1f(round(sin(beat_time * 1.6) + offset + phase)) * 8.);
+  return vec4f(C64Colors[u32(id)], 1.);
+}