add rotation to c31 hexagons

needs some cleanup but it's pretty efficient, at least

2 files changed, 19 insertions, 8 deletions

diff --git a/custom31.cginc b/custom31.cginc
index f44d185..67ecb78 100644
--- a/custom31.cginc
+++ b/custom31.cginc
@@ -6,20 +6,25 @@
 #include "math.cginc"
 #include "quilez.cginc"
 
-float c31_map(float3 p) {
+float c31_map(float3 p, float3 p_quant) {
   float2 hex_dim = float2(_Custom31_World_Hexagons_Tile_Radius, _Custom31_World_Hexagons_Tile_Thickness);
 
+  float3 axis_normal = normalize(hash33_fast(p_quant) * 2 - 1);
+  float theta = hash31_ff(p_quant) * TAU + _Time[1];
+  float4 quat = get_quaternion(axis_normal, theta);
+  p = rotate_vector(p, quat);
+
   return distance_from_hex_prism(p, hex_dim);
 }
 
-float3 c31_normal(float3 p) {
+float3 c31_normal(float3 p, float3 p_quant) {
   const float epsilon = 1e-3;
   const float3 xstep = float3(epsilon, 0, 0);
-  float d0 = c31_map(p);
+  float d0 = c31_map(p, p_quant);
   return normalize(float3(
-      c31_map(p + xstep.xyy) - d0,
-      c31_map(p + xstep.yxy) - d0,
-      c31_map(p + xstep.yyx) - d0));
+      c31_map(p + xstep.xyy, p_quant) - d0,
+      c31_map(p + xstep.yxy, p_quant) - d0,
+      c31_map(p + xstep.yyx, p_quant) - d0));
 }
 
 void apply_custom31_world(v2f i, inout Pbr pbr, inout float3 normal_tangent) {
@@ -45,7 +50,7 @@ void apply_custom31_world(v2f i, inout Pbr pbr, inout float3 normal_tangent) {
   [loop]
     for (uint ii = 0; ii < _Custom31_World_Ray_March_Steps; ++ii) {
       float3 p = ro + rd * d_acc;
-      d = c31_map(p);
+      d = c31_map(p, h_rounded);
       d_acc += d;
       if (d < _Custom31_World_Ray_March_Min_Dist) {
         break;
@@ -58,7 +63,7 @@ void apply_custom31_world(v2f i, inout Pbr pbr, inout float3 normal_tangent) {
   if (d < _Custom31_World_Ray_March_Min_Dist) {
     pbr.albedo.xyz = 1;
 
-    normal_tangent = c31_normal(ro + rd * d_acc);
+    normal_tangent = c31_normal(ro + rd * d_acc, h_rounded);
   } else {
     pbr.albedo.xyz = 0;
   }
diff --git a/math.cginc b/math.cginc
index 15d02eb..ee70495 100755
--- a/math.cginc
+++ b/math.cginc
@@ -67,6 +67,12 @@ float3 rotate_vector(float3 v, float4 q)
   return v + q.w * t + cross(q.xyz, t);
 }
 
+float4 get_quaternion(float3 axis_normal, float theta) {
+  float sint2, cost2;
+  sincos(theta*0.5, sint2, cost2);
+  return float4(axis_normal * sint2, cost2);
+}
+
 // Cartesian to packed cube hexagonal coordinates.
 // Stores (q + r, q, r), where the article's cube coordinates satisfy
 // q + r + s = 0 and s = -(q + r).