add hex grid tiling

6 files changed, 127 insertions, 34 deletions

diff --git a/3ner.shader b/3ner.shader
index d755f64..8d3a577 100644
--- a/3ner.shader
+++ b/3ner.shader
@@ -75,14 +75,27 @@ Shader "yum_food/3ner"
           [HideInInspector] m_end_Ray_Marching_Baked_Origins("Baked Origins", Float) = 0
           //endex
 
-          //ifex _Ray_Marching_Ball_Grid_Enabled==0
-          [HideInInspector] m_start_Ray_Marching_Ball_Grid("Ball Grid", Float) = 0
-            [ThryToggle(_RAY_MARCHING_BALL_GRID)] _Ray_Marching_Ball_Grid_Enabled("Enable", Float) = 0
-            _Ray_Marching_Ball_Grid_Radius("Radius", Float) = 1
-            _Ray_Marching_Ball_Grid_Count_X("Count X", Range(0,40)) = 5
-            _Ray_Marching_Ball_Grid_Count_Y("Count Y", Range(0,40)) = 5
-            _Ray_Marching_Ball_Grid_Count_Z("Count Z", Range(0,40)) = 5
-          [HideInInspector] m_end_Ray_Marching_Ball_Grid("Ball Grid", Float) = 0
+          //ifex _Ray_Marching_Cart_Grid_Enabled==0
+          [HideInInspector] m_start_Ray_Marching_Cart_Grid("Cart Grid", Float) = 0
+            [ThryToggle(_RAY_MARCHING_CART_GRID)] _Ray_Marching_Cart_Grid_Enabled("Enable", Float) = 0
+            _Ray_Marching_Cart_Grid_Count_X("Count X", Range(0,40)) = 5
+            _Ray_Marching_Cart_Grid_Count_Y("Count Y", Range(0,40)) = 5
+            _Ray_Marching_Cart_Grid_Count_Z("Count Z", Range(0,40)) = 5
+          [HideInInspector] m_end_Ray_Marching_Cart_Grid("Cart Grid", Float) = 0
+          //endex
+
+          //ifex _Ray_Marching_Hex_Grid_Enabled==0
+          [HideInInspector] m_start_Ray_Marching_Hex_Grid("Hex Grid", Float) = 0
+            [ThryToggle(_RAY_MARCHING_HEX_GRID)] _Ray_Marching_Hex_Grid_Enabled("Enable", Float) = 0
+            _Ray_Marching_Hex_Grid_Count("CountX", Range(0,40)) = 5
+          [HideInInspector] m_end_Ray_Marching_Hex_Grid("Hex Grid", Float) = 0
+          //endex
+
+          //ifex _Ray_Marching_Ball_Enabled==0
+          [HideInInspector] m_start_Ray_Marching_Ball("Ball", Float) = 0
+            [ThryToggle(_RAY_MARCHING_BALL)] _Ray_Marching_Ball_Enabled("Enable", Float) = 0
+            _Ray_Marching_Ball_Radius("Radius", Range(0,1)) = 1
+          [HideInInspector] m_end_Ray_Marching_Ball("Ball", Float) = 0
           //endex
 
         [HideInInspector] m_end_Ray_Marching("Ray Marching", Float) = 0
diff --git a/features.cginc b/features.cginc
index 49aa3e7..9b76cd4 100644
--- a/features.cginc
+++ b/features.cginc
@@ -84,8 +84,16 @@
 #pragma shader_feature_local _RAY_MARCHING_BAKED_ORIGINS
 //endex
 
-//ifex _Ray_Marching_Ball_Grid_Enabled==0
-#pragma shader_feature_local _RAY_MARCHING_BALL_GRID
+//ifex _Ray_Marching_Cart_Grid_Enabled==0
+#pragma shader_feature_local _RAY_MARCHING_CART_GRID
+//endex
+
+//ifex _Ray_Marching_Hex_Grid_Enabled==0
+#pragma shader_feature_local _RAY_MARCHING_HEX_GRID
+//endex
+
+//ifex _Ray_Marching_Ball_Enabled==0
+#pragma shader_feature_local _RAY_MARCHING_BALL
 //endex
 
 #endif  // __FEATURES_INC
diff --git a/globals.cginc b/globals.cginc
index 533e102..181e71f 100644
--- a/globals.cginc
+++ b/globals.cginc
@@ -134,6 +134,18 @@ float _Ray_Marching_Overstepping_Factor;
 int _Baked_Origins_UV_Channel_Index;
 #endif  // _RAY_MARCHING_BAKED_ORIGINS
 
+#if defined(_RAY_MARCHING_CART_GRID)
+float _Ray_Marching_Cart_Grid_Radius;
+float _Ray_Marching_Cart_Grid_Count_X;
+float _Ray_Marching_Cart_Grid_Count_Y;
+float _Ray_Marching_Cart_Grid_Count_Z;
+#endif  // _RAY_MARCHING_CART_GRID
+
+#if defined(_RAY_MARCHING_HEX_GRID)
+float _Ray_Marching_Hex_Grid_Radius;
+float _Ray_Marching_Hex_Grid_Count;
+#endif  // _RAY_MARCHING_HEX_GRID
+
 #if defined(_RAY_MARCHING_BALL_GRID)
 float _Ray_Marching_Ball_Grid_Radius;
 float _Ray_Marching_Ball_Grid_Count_X;
@@ -141,4 +153,8 @@ float _Ray_Marching_Ball_Grid_Count_Y;
 float _Ray_Marching_Ball_Grid_Count_Z;
 #endif  // _RAY_MARCHING_BALL_GRID
 
+#if defined(_RAY_MARCHING_BALL)
+float _Ray_Marching_Ball_Radius;
+#endif  // _RAY_MARCHING_BALL
+
 #endif  // __GLOBALS_INC
diff --git a/math.cginc b/math.cginc
index 58a9c08..f188a91 100644
--- a/math.cginc
+++ b/math.cginc
@@ -74,5 +74,20 @@ float2 hex_to_cart(float3 cart) {
       (cart[1] - cart[2]) * SQRT_3_OVER_2);
 }
 
+
+float3 round_hex(float3 hex_coord) {
+    float3 rounded = round(hex_coord);
+    float3 diff = abs(rounded - hex_coord);
+    float error = rounded.x - rounded.y - rounded.z;
+
+    float3 max_mask = float3(
+        diff.x > diff.y && diff.x > diff.z,
+        diff.y > diff.x && diff.y > diff.z,
+        diff.z > diff.x && diff.z > diff.y);
+
+    rounded += error * float3(-1, 1, 1) * max_mask;
+    return rounded;
+}
+
 #endif  // __MATH_INC
 
diff --git a/ray_marching.cginc b/ray_marching.cginc
index b13bee0..57a3dff 100644
--- a/ray_marching.cginc
+++ b/ray_marching.cginc
@@ -42,12 +42,63 @@ void ray_march(inout v2f i) {
   const uint kMaxIter = _Ray_Marching_Max_Iter;
   float d_cur;
   float d_acc = 0;
+  float3 hit_pos;
   for (uint ii = 0; ii < kMaxIter; ++ii) {
     float3 p = ro + rd * d_acc;
     d_cur = 1e9;
-#if defined(_RAY_MARCHING_BALL_GRID)
-    float3 count = float3(_Ray_Marching_Ball_Grid_Count_X, _Ray_Marching_Ball_Grid_Count_Y, _Ray_Marching_Ball_Grid_Count_Z);
-    d_cur = min(d_cur, map_ball_grid(p, count));
+
+    // Coordinate system transformations.
+#if defined(_RAY_MARCHING_CART_GRID)
+    {
+      float3 count = float3(_Ray_Marching_Cart_Grid_Count_X, _Ray_Marching_Cart_Grid_Count_Y, _Ray_Marching_Cart_Grid_Count_Z);
+      float3 period = 1.0f / count;
+      period *= 2;
+      float3 half_period = period*0.5f;
+      float3 which = floor((p + half_period) / period);
+      if (any(abs(which) > count/2)) {
+        p = 1e6;
+      } else {
+        p = glsl_mod(p + half_period, period) - half_period;
+      }
+    }
+#endif
+#if defined(_RAY_MARCHING_HEX_GRID)
+    {
+      const float3 count = _Ray_Marching_Hex_Grid_Count * 0.5f;
+      const float3 period = 1.0f / count;
+      const float3 hex = cart_to_hex(p.xy);
+
+      float half_period = period * 0.5;
+      float3 which = floor((hex + half_period) / period);
+
+      // The original code here was this:
+      //   p_hex = glsl_mod(p_hex + half_period, period) - half_period;
+      //
+      // But you can simplify it. Given the definition of glsl_mod:
+      //   #define glsl_mod(x,y) (((x)-(y)*floor((x)/(y))))
+      //
+      // You can plug in terms:
+      //  (p_hex + half_period) - (period) * floor((p_hex + half_period) / period)
+      //  = p_hex + half_period - period * floor(p_hex/period + 0.5)
+      //
+      // For all x,
+      //  round(x) = floor(x + 0.5)
+      //
+      // Continuing to simplify:
+      //  (p_hex + half_period - period * round(p_hex/period)) - half_period
+      //  = p_hex - period * round(p_hex / period)
+      const float3 hex_inst = hex - period * round_hex(hex / period);
+
+      p.xy = (any(abs(which) > count/2) ? 1e9 : hex_to_cart(hex_inst));
+    }
+#endif
+
+    // Sdfs.
+#if defined(_RAY_MARCHING_BALL)
+    {
+      float r = _Ray_Marching_Ball_Radius;
+      d_cur = min(d_cur, map_ball(p, _Ray_Marching_Ball_Radius));
+    }
 #endif
 
 #if defined(_RAY_MARCHING_OVERSTEP)
@@ -56,6 +107,7 @@ void ray_march(inout v2f i) {
 
     d_acc += d_cur;
     if (abs(d_cur) < kMinDist) {
+      hit_pos = p;
       break;
     }
     if (d_acc > kMaxDist) {
@@ -67,13 +119,14 @@ void ray_march(inout v2f i) {
     discard;
   }
 
-  // TODO clip / hit detection
-  float3 lclPos = ro + rd * d_acc;
+  float3 lclPos = hit_pos;
   float3 lclNorm;
   float3 lclTan;
-#if defined(_RAY_MARCHING_BALL_GRID)
-  float3 count = float3(_Ray_Marching_Ball_Grid_Count_X, _Ray_Marching_Ball_Grid_Count_Y, _Ray_Marching_Ball_Grid_Count_Z);
-  map_ball_grid_normal(count, lclPos, lclNorm, lclTan);
+#if defined(_RAY_MARCHING_BALL)
+  {
+    float r = _Ray_Marching_Ball_Radius;
+    map_ball_normal(r, lclPos, lclNorm, lclTan);
+  }
 #endif
 
   i.objPos = lclPos;
@@ -83,4 +136,3 @@ void ray_march(inout v2f i) {
 }
 
 #endif  // __RAY_MARCHING_INC
-
diff --git a/ray_marching_maps.slang b/ray_marching_maps.slang
index 3c83a19..002ef90 100644
--- a/ray_marching_maps.slang
+++ b/ray_marching_maps.slang
@@ -32,25 +32,14 @@
   R3R1_AUTODIFF_BASIS_VECTORS(fun, __VA_ARGS__);              \
   R3R1_DEFORM_NORMAL_AND_TANGENT(normal, tangent)
 
-// Just trace a sphere of radius 0.1 for now.
 [Differentiable]
-public float map_ball_grid(float3 p, no_diff float3 count) {
-  float3 period = 1.0f / count;
-  period *= 2;
-  float3 half_period = period*0.5f;
-  float3 which = floor((p + half_period) / period);
-  if (any(abs(which) > count/2)) {
-    p = 1e6;
-  } else {
-    p = glsl_mod(p + half_period, period) - half_period;
-  }
-
-  return length(p) - half_period.x;
+public float map_ball(float3 p, no_diff float r) {
+  return length(p) - r;
 }
 
-public void map_ball_grid_normal(float3 count, inout float3 xyz, inout float3 normal,
+public void map_ball_normal(float r, inout float3 xyz, inout float3 normal,
     inout float3 tangent) {
-  R3R1_RAY_MARCH_NORMALS(xyz, normal, tangent, map_ball_grid, count);
+  R3R1_RAY_MARCH_NORMALS(xyz, normal, tangent, map_ball, r);
 }
 
 #endif  // __RAY_MARCHING_MAPS_INC