Begin work on aurora gimmick

1 files changed, 65 insertions, 0 deletions

diff --git a/aurora.cginc b/aurora.cginc
new file mode 100644
index 0000000..c926482
--- /dev/null
+++ b/aurora.cginc
@@ -0,0 +1,65 @@
+#include "globals.cginc"
+#include "interpolators.cginc"
+#include "math.cginc"
+#include "noise.cginc"
+#include "cnlohr.cginc"
+
+#ifndef __AURORA_INC
+#define __AURORA_INC
+
+struct AuroraPBR {
+  float4 albedo;
+  float3 diffuse;
+  float depth;
+};
+
+float2 rotate2D(float2 v, float theta) {
+  return mul(float2x2(
+        cos(theta), -sin(theta),
+        sin(theta), cos(theta)), v);
+}
+
+AuroraPBR getAurora(v2f i) {
+  AuroraPBR result;
+  result.albedo.a = 1;
+
+  // Map onto [-1, 1]
+  float t = _Time[1];
+  float2 uv = i.uv0;
+  float c = 0;
+
+  uv = rotate2D(uv, t * .101);
+  uv *= 0.9;
+  float c_term = sin(3.14159265 * uv.x * uv.x + t) - 0.25;
+  c = c_term * c_term;
+
+  uv = rotate2D(uv, -t * .67);
+  c_term = (sin(-3.14159265 * uv.x * uv.x * 4 + t/4) - 0.25) * .5;
+  c += c_term * c_term;
+
+  uv = rotate2D(uv, t * .31);
+  c += (sin(-3.14159265 * uv.y * uv.y * 16 + t/8) - 0.25) * .25;
+
+  uv = rotate2D(uv, t * .15);
+  c += (sin(-3.14159265 * uv.x * uv.y * 16 + t/16) - 0.25) * .125;
+
+  c *= 0.5;
+
+  c -= sin(3.14159265 * uv.x * uv.y * 16) * .5 + 0.5;
+
+  const float2 uv_c = i.uv0 * 2.0 - 1;
+  float center_distance_term = saturate(1.0 - dot(uv_c, uv_c));
+  c *= center_distance_term * center_distance_term * center_distance_term * center_distance_term;
+
+  result.albedo.rgb = saturate(c);
+
+  result.diffuse = 0;
+
+  float4 clip_pos = mul(UNITY_MATRIX_VP, float4(i.worldPos, 1.0));
+  result.depth = clip_pos.z / clip_pos.w;
+
+  return result;
+}
+
+#endif  // __AURORA_INC
+