c31: continue work on hex ray marcher

1 files changed, 44 insertions, 30 deletions

diff --git a/custom31.cginc b/custom31.cginc
index 6f29403..f44d185 100644
--- a/custom31.cginc
+++ b/custom31.cginc
@@ -3,51 +3,65 @@
 
 #include "globals.cginc"
 #include "interpolators.cginc"
+#include "math.cginc"
+#include "quilez.cginc"
 
-float map(float3 p) {
-  return length(p) - 0.1;
+float c31_map(float3 p) {
+  float2 hex_dim = float2(_Custom31_World_Hexagons_Tile_Radius, _Custom31_World_Hexagons_Tile_Thickness);
+
+  return distance_from_hex_prism(p, hex_dim);
+}
+
+float3 c31_normal(float3 p) {
+  const float epsilon = 1e-3;
+  const float3 xstep = float3(epsilon, 0, 0);
+  float d0 = c31_map(p);
+  return normalize(float3(
+      c31_map(p + xstep.xyy) - d0,
+      c31_map(p + xstep.yxy) - d0,
+      c31_map(p + xstep.yyx) - d0));
 }
 
 void apply_custom31_world(v2f i, inout Pbr pbr, inout float3 normal_tangent) {
 #if defined(_CUSTOM31_WORLD)
-  // We will raymarch in (tangent, binormal, normal) coordinates.
-  // Make an expanded homogeneous tbn matrix to support moving back and forth.
-  // This first incarnation moves from world to tangent.
-  float4x4 tbn = float4x4(
-      pbr.tbn[0], 0,
-      pbr.tbn[1], 0,
-      pbr.tbn[2], 0,
-      0, 0, 0,    1);
-  tbn = mul(tbn, unity_WorldToObject);
-
-  float3 ro = mul(tbn, float4(i.worldPos, 1));
-  float3 rd = normalize(mul((float3x3) tbn, i.worldPos - _WorldSpaceCameraPos));
+  // We ray march in tangent (TBN) space.
+  float3 ro = float3(i.uv01.xy, 0);
+  float3 rd_world = normalize(i.worldPos - _WorldSpaceCameraPos);
+  float3 rd = normalize(mul(pbr.tbn, rd_world));
+
+#if defined(_CUSTOM31_WORLD_HEXAGONS)
+  // Apply hexagonal domain repetition.
+  float domain_rep_period = _Custom31_World_Hexagons_Grid_Scale;
+  // yx swizzle rotates hexagons 90 degrees
+  float3 h = cart_to_hex(ro.yx);
+  float3 h_rounded = round_hex(h / domain_rep_period) * domain_rep_period;
+  ro.xy = hex_to_cart(h - h_rounded).yx;
+  ro.z += _Custom31_World_Hexagons_Tile_Thickness;
+  ro.z += _Custom31_World_Ray_March_Min_Dist;
+#endif
 
   float d_acc = 0;
   float d;
-  const float MIN_DIST = 1e-3;
-  const float MAX_DIST = 1;
   [loop]
-  for (uint ii = 0; ii < 10; ++ii) {
-    float3 p = ro + rd * d_acc;
-    d = map(p);
-    d_acc += d;
-    if (d < MIN_DIST) {
-      break;
+    for (uint ii = 0; ii < _Custom31_World_Ray_March_Steps; ++ii) {
+      float3 p = ro + rd * d_acc;
+      d = c31_map(p);
+      d_acc += d;
+      if (d < _Custom31_World_Ray_March_Min_Dist) {
+        break;
+      }
+      if (d > _Custom31_World_Ray_March_Max_Dist) {
+        break;
+      }
     }
-    if (d > MAX_DIST) {
-      break;
-    }
-  }
 
-  if (d < MIN_DIST) {
+  if (d < _Custom31_World_Ray_March_Min_Dist) {
     pbr.albedo.xyz = 1;
+
+    normal_tangent = c31_normal(ro + rd * d_acc);
   } else {
     pbr.albedo.xyz = 0;
   }
-
-  float3 p = ro + rd * d_acc;
-  p = mul(float4(p, 1), tbn);
 #endif
 }