Start work on new halo tech

1 files changed, 137 insertions, 0 deletions

diff --git a/halos.cginc b/halos.cginc
new file mode 100644
index 0000000..aa0b731
--- /dev/null
+++ b/halos.cginc
@@ -0,0 +1,137 @@
+#ifndef __HALOS_INC
+#define __HALOS_INC
+
+#include "globals.cginc"
+#include "interpolators.cginc"
+#include "math.cginc"
+
+#if defined(_GIMMICK_HALO_00)
+struct Halo00Params {
+  float3 period;
+  float3 count;
+  float2 uv;
+};
+struct Halo00PBR {
+  float4 albedo;
+  float3 normal;
+};
+
+float halo00_map(float3 p, float2 e)
+{
+  return length(p) - 0.1;
+}
+
+float halo00_map_dr(
+    float3 p,
+    Halo00Params params,
+    out float3 which
+    )
+{
+  which = round(p / params.period);
+  // Direction to nearest neighboring cell.
+  float3 min_d = p - params.period * which;
+  float3 o = sign(min_d);
+
+  float d = 1E9;
+  float3 which_tmp = which;
+  for (int xi = 0; xi < 1; xi++)
+  for (int yi = 0; yi < 1; yi++)
+  {
+    float3 rid = which + float3(xi, yi, 0) * o;
+    rid = clamp(rid, ceil(-(params.count)*0.5), floor((params.count-1)*0.5));
+    float3 r = p - params.period * rid;
+    float2 e = 0;
+    /*
+    float2 e = float2(
+        rand3(rid / 100.0),
+        rand3(rid / 100.0 + 1));
+    */
+    float cur_d = halo00_map(r, e);
+    which_tmp = 
+        (cur_d < d ? rid : which_tmp);
+    d = min(d, cur_d);
+  }
+
+  which = which_tmp;
+  return d;
+}
+
+float3 halo00_calc_normal(float3 p, Halo00Params params)
+{
+    const float3 small_step = float3(0.0001, 0.0, 0.0);
+
+    // TODO do we need full central differences?
+    float3 which;
+    float gradient_x = halo00_map_dr(p + small_step.xyy, params, which) -
+      halo00_map_dr(p - small_step.xyy, params, which);
+    float gradient_y = halo00_map_dr(p + small_step.yxy, params, which) -
+      halo00_map_dr(p - small_step.yxy, params, which);
+    float gradient_z = halo00_map_dr(p + small_step.yyx, params, which) -
+      halo00_map_dr(p - small_step.yyx, params, which);
+
+    float3 normal = float3(gradient_x, gradient_y, gradient_z);
+
+    return normalize(normal);
+}
+
+void __halo00_march(float3 ro, float3 rd, Halo00Params params, out Halo00PBR result)
+{
+  float total_distance_traveled = 0.0;
+  const float MINIMUM_HIT_DISTANCE = 0.001;
+  const float MAXIMUM_TRACE_DISTANCE = 10.0;
+  
+  ro -= (1 - (params.count % 2)) * params.period * 0.5;
+
+#define HALO00_MARCH_STEPS 30
+  float distance_to_closest;
+  float3 current_position;
+  float3 which;
+  for (int i = 0; i < HALO00_MARCH_STEPS; i++)
+  {
+    current_position = ro + total_distance_traveled * rd;
+
+    distance_to_closest = halo00_map_dr(current_position, params, which);
+
+    if (distance_to_closest < MINIMUM_HIT_DISTANCE) 
+    {
+      break;
+    }
+
+    if (total_distance_traveled > MAXIMUM_TRACE_DISTANCE)
+    {
+      break;
+    }
+    total_distance_traveled += distance_to_closest;
+  }
+
+  if (distance_to_closest < MINIMUM_HIT_DISTANCE) {
+    result.albedo = 1;
+    result.normal = halo00_calc_normal(current_position, params);
+    return;
+  }
+
+  result.albedo = 0;
+  result.normal = 0;
+  return;
+}
+
+Halo00PBR halo00_march(float3 worldPos, float2 uv)
+{
+  Halo00PBR result;
+  Halo00Params params;
+  params.period = 0.2;
+  params.count = 5;
+  params.uv = uv;
+
+  float3 camera_position = mul(unity_WorldToObject, float4(_WorldSpaceCameraPos.xyz, 1));
+  float3 ro = camera_position;
+  float3 rd = normalize(mul(unity_WorldToObject, float4(worldPos - _WorldSpaceCameraPos.xyz, 1)));
+
+  __halo00_march(ro, rd, params, result);
+
+  return result;
+}
+
+#endif  // _GIMMICK_HALO_00
+
+#endif  // _HALOS_INC