From f1fc3bd51a90432ddb6b7cbc86b8383c923b0dd8 Mon Sep 17 00:00:00 2001
From: yum <yum.food.vr@gmail.com>
Date: Wed, 13 Aug 2025 16:51:23 -0700
Subject: add hypotrochoid gimmick

---
 2ner.cginc | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to '2ner.cginc')

diff --git a/2ner.cginc b/2ner.cginc
index 1e6af31..0e6fa82 100644
--- a/2ner.cginc
+++ b/2ner.cginc
@@ -25,6 +25,7 @@
 #include "ssao.cginc"
 #include "ssfd.cginc"
 #include "tessellation.cginc"
+#include "trochoid.cginc"
 #include "unigram_letter_grid.cginc"
 #include "vertex_domain_warping.cginc"
 #include "yum_brdf.cginc"
@@ -117,6 +118,11 @@ v2f vert(appdata v) {
   v.vertex.xyz = domainWarpVertexPosition(v.vertex.xyz);
 #endif
 
+#if defined(_TROCHOID)
+  o.orig_pos = v.vertex.xyz;
+  v.vertex.xyz = trochoid_map(v.vertex.xyz);
+#endif
+
 #if defined(OUTLINE_PASS)
   [branch]
   if (!_Outlines_Enabled_Dynamic) {
@@ -299,6 +305,7 @@ float4 frag(v2f i, uint facing : SV_IsFrontFace
 
 #if defined(_SHATTER_WAVE)
   calcNormalInScreenSpace(i.normal, i.objPos);
+  i.normal = UnityObjectToWorldNormal(i.normal);
 #endif
 
 #if defined(_SHATTER_WAVE) || defined(_VERTEX_DOMAIN_WARPING) || defined(_TESSELLATION_HEIGHTMAP)
@@ -399,6 +406,24 @@ float4 frag(v2f i, uint facing : SV_IsFrontFace
 #endif
 #endif
 
+#if defined(_TROCHOID)
+  float3 normal_obj = trochoid_normal(i.orig_pos);
+
+  // We need tangents that are perpendicular to the new normal.
+  // A common way to generate them is to cross with a fixed "up" vector.
+  float3 tangent_obj = normalize(cross(normal_obj, float3(0, 1, 0)));
+  float3 binormal_obj = cross(normal_obj, tangent_obj);
+
+  i.normal = UnityObjectToWorldNormal(normal_obj);
+  i.tangent = float4(normalize(mul((float3x3)unity_ObjectToWorld, tangent_obj)), 1);
+  i.binormal = normalize(mul((float3x3)unity_ObjectToWorld, binormal_obj));
+  i.normal *= facing ? 1 : -1;
+
+  float theta = 1 - atan2(i.orig_pos.y, i.orig_pos.x) / PI;
+  float3 color = _Trochoid_Color_Ramp.SampleLevel(linear_clamp_s, float2(theta, 0.5), 0).rgb;
+  pbr.albedo.xyz = color;
+#endif
+
 #if defined(_HARNACK_TRACING)
   HarnackTracingOutput harnack_output = HarnackTracing(i);
   pbr.albedo = float4(1, 1, 1, 0.2);
-- 
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