From 5629d437dae33c2cdb283a139f8632fb613c0a43 Mon Sep 17 00:00:00 2001
From: yum <yum.food.vr@gmail.com>
Date: Tue, 8 Apr 2025 19:05:47 -0700
Subject: Fix backface normals, fix depth writing precision issues

---
 2ner.cginc          | 23 ++++++++++++++++++++---
 interpolators.cginc |  4 ++--
 tessellation.cginc  |  2 +-
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/2ner.cginc b/2ner.cginc
index d8bc010..065015f 100644
--- a/2ner.cginc
+++ b/2ner.cginc
@@ -156,7 +156,7 @@ v2f vert(appdata v) {
   return o;
 }
 
-float4 frag(v2f i
+float4 frag(v2f i, uint facing : SV_IsFrontFace
 #if defined(_HARNACK_TRACING) || defined(_SHATTER_WAVE) || defined(_VERTEX_DOMAIN_WARPING)
   , out float depth : SV_DepthLessEqual
 #endif
@@ -168,6 +168,8 @@ float4 frag(v2f i
   // Not necessarily normalized after interpolation
   i.normal = normalize(i.normal);
 
+  i.normal *= facing ? 1 : -1;
+
   i.normal = UnityObjectToWorldNormal(i.normal);
   i.tangent = UnityObjectToWorldNormal(i.tangent);
   i.binormal = UnityObjectToWorldNormal(i.binormal);
@@ -178,8 +180,23 @@ float4 frag(v2f i
 
 #if defined(_SHATTER_WAVE) || defined(_VERTEX_DOMAIN_WARPING)
   {
-    float4 clip_pos = mul(UNITY_MATRIX_VP, float4(i.worldPos, 1.0));
-    depth = clip_pos.z / clip_pos.w;
+    [branch]
+    if (
+        false
+#if defined(_SHATTER_WAVE)
+        || any(_Shatter_Wave_Amplitude > 1E-4)
+#endif
+#if defined(_VERTEX_DOMAIN_WARPING)
+        || _Vertex_Domain_Warping_Octaves > 0.1
+#endif
+    ) {
+      float4 clip_pos = UnityObjectToClipPos(i.objPos);
+      depth = clip_pos.z / clip_pos.w;
+    } else {
+      // Perspective division takes place before the fragment shader, so we
+      // don't have to divide again.
+      depth = i.pos.z;
+    }
   }
 #endif
 
diff --git a/interpolators.cginc b/interpolators.cginc
index b003abf..59f339a 100644
--- a/interpolators.cginc
+++ b/interpolators.cginc
@@ -17,9 +17,9 @@ struct v2f {
 #if defined(_TESSELLATION)
 	float4 tpos         : INTERNALTESSPOS;
 #endif
-	float4 pos         : SV_POSITION;
+	linear noperspective centroid float4 pos         : SV_POSITION;
 	float4 uv01        : TEXCOORD0;
-	float3 objPos      : TEXCOORD1;
+	float4 objPos      : TEXCOORD1;
 	float3 worldPos    : TEXCOORD2;
 	float3 normal      : TEXCOORD3;
 	float3 tangent     : TEXCOORD4;
diff --git a/tessellation.cginc b/tessellation.cginc
index af4bd3b..cc47057 100644
--- a/tessellation.cginc
+++ b/tessellation.cginc
@@ -141,7 +141,7 @@ v2f domain(
 #endif
 
   o.pos      = UnityObjectToClipPos(o.objPos);
-  o.worldPos = mul(unity_ObjectToWorld, float4(o.objPos, 1.0)).xyz;
+  o.worldPos = mul(unity_ObjectToWorld, o.objPos).xyz;
   o.eyeVec.xyz = normalize(o.worldPos - _WorldSpaceCameraPos);
   o.eyeVec.w = 1;
 
-- 
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