Grass: add crude instancing code

9 files changed, 1879 insertions, 1 deletions

diff --git a/3ner.cginc b/3ner.cginc
index 02081a9..e675bc2 100755
--- a/3ner.cginc
+++ b/3ner.cginc
@@ -15,6 +15,7 @@
 #include "lighting.cginc"
 #include "globals.cginc"
 #include "interpolators.cginc"
+#include "instancing.cginc"
 #include "ray_marching.cginc"
 #include "vertex.cginc"
 #include "impostor.cginc"
@@ -30,6 +31,9 @@ v2f vert(appdata v) {
   UNITY_TRANSFER_INSTANCE_ID(v, o);
   UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
 
+  // Apply instance texture offset transformation if enabled
+  instancing_vert(v);
+
 #if defined(_IMPOSTORS)
   impostor_vert(v.vertex.xyz);
 #endif
@@ -262,6 +266,9 @@ float4 frag(v2f i, uint facing : SV_IsFrontFace
   return 0;
 #endif
 
+  // Apply instancing effects (e.g., distance culling)
+  instancing_frag(i);
+
 #if defined(_RAY_MARCHING)
   const bool is_fragment = true;
   ray_march(i, is_fragment);
diff --git a/3ner.shader b/3ner.shader
index dce0e18..e411ada 100755
--- a/3ner.shader
+++ b/3ner.shader
@@ -426,12 +426,23 @@ Shader "yum_food/3ner"
       [DoNotAnimate][HideInInspector] Instancing ("Instancing", Float) = 0
       //ifex Instancing==0
       [HideInInspector] m_start_Instancing("Instancing", Float) = 0
-        //ifex _Instance_Distance_Culling_Enabled
+        //ifex _Instance_Distance_Culling_Enabled==0
         [HideInInspector] m_start_Instance_Distance_Culling("Distance Culling", Float) = 0
           [ThryToggle(_INSTANCE_DISTANCE_CULLING)] _Instance_Distance_Culling_Enabled("Enable", Float) = 0
           _Instance_Distance_Culling_Distance("Distance (m)", Float) = 10
         [HideInInspector] m_end_Instance_Distance_Culling("Instance Distance Culling", Float) = 0
         //endex
+        //ifex _Instance_Texture_Offset_Enabled==0
+        [HideInInspector] m_start_Instance_Texture_Offset("Texture Offset", Float) = 0
+          [ThryToggle(_INSTANCE_TEXTURE_OFFSET)] _Instance_Texture_Offset_Enabled("Enable", Float) = 0
+          _Instance_Texture_Offset_Data_Tex("Instance Data Texture", 2D) = "black" {}
+          _Instance_Texture_Offset_Cell_Dimensions("Cell Dimensions", Vector) = (1, 1, 1, 0)
+          _Instance_Texture_Offset_Angle_Randomization("Angle Randomization", Vector) = (0, 0, 0, 0)
+          _Instance_Texture_Offset_Scale_Randomization("Scale Randomization", Float) = 0
+          _Instance_Texture_Offset_Base_Scale("Base Scale", Vector) = (1, 1, 1, 0)
+          _Instance_Texture_Offset_Base_Rotation("Base Rotation (Quaternion)", Vector) = (0, 0, 0, 1)
+        [HideInInspector] m_end_Instance_Texture_Offset("Instance Texture Offset", Float) = 0
+        //endex
       [HideInInspector] m_end_Instancing("Instancing", Float) = 0
       //endex
 
diff --git a/Scripts/GrassGridBlit.shader b/Scripts/GrassGridBlit.shader
new file mode 100644
index 0000000..f4dc872
--- /dev/null
+++ b/Scripts/GrassGridBlit.shader
@@ -0,0 +1,77 @@
+Shader "yum_food/GrassGridBlit"
+{
+    Properties
+    {
+    }
+    SubShader
+    {
+        Tags { "RenderType"="Opaque" }
+        LOD 100
+
+        Pass
+        {
+            CGPROGRAM
+            #pragma vertex vert
+            #pragma fragment frag
+
+            #include "UnityCG.cginc"
+
+            struct appdata
+            {
+                float4 vertex : POSITION;
+                float2 uv : TEXCOORD0;
+            };
+
+            struct v2f
+            {
+                float2 uv : TEXCOORD0;
+                float4 vertex : SV_POSITION;
+            };
+
+            // Grid parameters
+            float3 _PlayerGridPos;    // Player's grid cell position (x, y, z)
+            int3 _GridCount;          // Number of instances along each axis
+            int3 _GridHalf;           // Half dimensions for centering around player
+            int2 _TexDimensions;      // Texture width and height
+
+            v2f vert (appdata v)
+            {
+                v2f o;
+                o.vertex = UnityObjectToClipPos(v.vertex);
+                o.uv = v.uv;
+                return o;
+            }
+
+            float4 frag (v2f i) : SV_Target
+            {
+                // Convert UV to pixel coordinates
+                int2 pixelCoord = int2(i.uv.x * _TexDimensions.x, i.uv.y * _TexDimensions.y);
+
+                // Convert pixel coordinate to instance index
+                int instanceID = pixelCoord.x + pixelCoord.y * _TexDimensions.x;
+
+                // Calculate total valid instances
+                int totalInstances = _GridCount.x * _GridCount.y * _GridCount.z;
+
+                // If this pixel is beyond valid instances, output invalid marker
+                if (instanceID >= totalInstances) {
+                    return float4(0, 0, 0, -1);  // Alpha = -1 marks invalid
+                }
+
+                // Convert instance index to local grid coordinates (0 to GridCount-1)
+                int localX = instanceID % _GridCount.x;
+                int localY = (instanceID / _GridCount.x) % _GridCount.y;
+                int localZ = instanceID / (_GridCount.x * _GridCount.y);
+
+                // Convert to world grid coordinates centered around player
+                int worldX = _PlayerGridPos.x - _GridHalf.x + localX;
+                int worldY = _PlayerGridPos.y - _GridHalf.y + localY;
+                int worldZ = _PlayerGridPos.z - _GridHalf.z + localZ;
+
+                // Store world grid coordinates in RGB channels, alpha = 0 marks valid
+                return float4(worldX, worldY, worldZ, 0);
+            }
+            ENDCG
+        }
+    }
+}
diff --git a/Scripts/InstanceGrass.asset b/Scripts/InstanceGrass.asset
new file mode 100755
index 0000000..3dd3bc4
--- /dev/null
+++ b/Scripts/InstanceGrass.asset
@@ -0,0 +1,1265 @@
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diff --git a/Scripts/InstanceGrass.cs b/Scripts/InstanceGrass.cs
new file mode 100755
index 0000000..3c0d8f6
--- /dev/null
+++ b/Scripts/InstanceGrass.cs
@@ -0,0 +1,343 @@
+using UdonSharp;
+using UnityEngine;
+using VRC.SDKBase;
+
+#if UNITY_EDITOR && !COMPILER_UDONSHARP
+using UnityEditor;
+using System.IO;
+#endif
+
+public class InstanceGrass : UdonSharpBehaviour
+{
+  [SerializeField] public GameObject prefab_;
+  // The density of instances, in instances per meter.
+  [SerializeField] public float density_;
+  // The extent along each cardinal axis where instances will be rendered, in
+  // meters. I.e. render inside a cube with edges this long.
+  [SerializeField] public Vector3 extent_meters_;
+  [SerializeField] public Vector3 angle_randomization_;
+  [SerializeField] public float scale_randomization_;
+
+  // GPU mode settings
+  [SerializeField] public Vector3Int max_grid_size_ = new Vector3Int(512, 1, 512);  // Maximum grid dimensions for GPU mode
+  [SerializeField] public Material blit_material_;  // Auto-generated in editor, set by custom editor
+
+  private Mesh mesh_;
+  private Material instance_material_;  // Extracted from prefab
+  private Transform base_transform_;
+  private Vector3 cell_dim_;
+  private Vector3 inv_cell_dim_;
+  private Vector3Int count_;
+  private int total_instances_;
+  private bool initialized_;
+
+  // Track fields to detect runtime changes.
+  private float density_live_;
+  private Vector3 extent_meters_live_;
+  private Vector3 angle_randomization_live_;
+  private float scale_randomization_live_;
+
+  // GPU-specific resources
+  private RenderTexture instance_data_tex_;
+  private Matrix4x4[] identity_transforms_;  // All identity matrices
+  private int tex_width_;
+  private int tex_height_;
+
+  private void Init() {
+    // Extract components from prefab.
+    if (prefab_ != null) {
+      MeshFilter mesh_filter = prefab_.GetComponent<MeshFilter>();
+      if (mesh_filter == null && prefab_.transform.childCount > 0) {
+        mesh_filter = prefab_.GetComponentInChildren<MeshFilter>();
+      }
+      if (mesh_filter != null) {
+        mesh_ = mesh_filter.sharedMesh;
+        if (mesh_ == null) {
+          mesh_ = mesh_filter.mesh;
+        }
+      } else {
+        Debug.LogError("[Grass::Debug] Could not find MeshFilter on prefab or children.");
+      }
+
+      MeshRenderer mesh_renderer = prefab_.GetComponent<MeshRenderer>();
+      if (mesh_renderer == null && prefab_.transform.childCount > 0) {
+        mesh_renderer = prefab_.GetComponentInChildren<MeshRenderer>();
+      }
+      if (mesh_renderer != null) {
+        Material[] materials = mesh_renderer.sharedMaterials;
+        if (materials != null && materials.Length > 0) {
+          instance_material_ = materials[0];
+        } else {
+          Debug.LogError("[Grass::Debug] MeshRenderer has no materials.");
+        }
+      } else {
+        Debug.LogError("[Grass::Debug] Could not find MeshRenderer on prefab.");
+      }
+
+      base_transform_ = prefab_.transform;
+      Debug.Log($"[Grass::Debug] Prefab transform - pos:{base_transform_.position}, rot:{base_transform_.rotation.eulerAngles}, scale:{base_transform_.localScale}");
+    } else {
+      Debug.LogError("[Grass::Debug] prefab is null in Init().");
+    }
+
+    density_ = Mathf.Max(1e-6f, density_);
+    extent_meters_ = Vector3.Max(Vector3.one * 1e-6f, extent_meters_);
+    angle_randomization_ = new Vector3(
+        Mathf.Clamp(angle_randomization_.x, 0f, 180f),
+        Mathf.Clamp(angle_randomization_.y, 0f, 180f),
+        Mathf.Clamp(angle_randomization_.z, 0f, 180f));
+
+    // Use max_grid_size_ directly for GPU mode
+    count_ = Vector3Int.Min(max_grid_size_, new Vector3Int(
+        Mathf.Max(1, Mathf.RoundToInt(density_ * extent_meters_.x)),
+        Mathf.Max(1, Mathf.RoundToInt(density_ * extent_meters_.y)),
+        Mathf.Max(1, Mathf.RoundToInt(density_ * extent_meters_.z))));
+
+    cell_dim_ = new Vector3(
+        extent_meters_.x / count_.x,
+        extent_meters_.y / count_.y,
+        extent_meters_.z / count_.z);
+    inv_cell_dim_ = new Vector3(
+        1f / cell_dim_.x,
+        1f / cell_dim_.y,
+        1f / cell_dim_.z);
+
+    total_instances_ = count_.x * count_.y * count_.z;
+
+    // Calculate texture dimensions (power of 2, minimum 256x256)
+    int min_tex_size = Mathf.CeilToInt(Mathf.Sqrt(total_instances_));
+    tex_width_ = Mathf.Max(256, Mathf.NextPowerOfTwo(min_tex_size));
+    tex_height_ = tex_width_;
+
+    // Create instance data texture
+    if (instance_data_tex_ != null) {
+      instance_data_tex_.Release();
+    }
+    instance_data_tex_ = new RenderTexture(tex_width_, tex_height_, 0, RenderTextureFormat.ARGBFloat);
+    instance_data_tex_.filterMode = FilterMode.Point;
+    instance_data_tex_.Create();
+
+    // Create transform array with encoded instance IDs - must match actual draw count
+    int actual_draw_count = tex_width_ * tex_height_;
+    if (identity_transforms_ == null || identity_transforms_.Length != actual_draw_count) {
+      identity_transforms_ = new Matrix4x4[actual_draw_count];
+      for (int i = 0; i < actual_draw_count; i++) {
+        // Encode instance ID in the matrix translation component
+        // We'll put the ID in the X component, which the shader will read
+        Matrix4x4 m = Matrix4x4.identity;
+        m.m03 = i; // Store instance ID in translation.x
+        identity_transforms_[i] = m;
+      }
+    }
+
+    if (mesh_ != null) {
+      // Set huge bounds so culling doesn't interfere
+      mesh_.bounds = new Bounds(Vector3.zero, Vector3.one * 10000f);
+    }
+
+    density_live_ = density_;
+    extent_meters_live_ = extent_meters_;
+    angle_randomization_live_ = angle_randomization_;
+    scale_randomization_live_ = scale_randomization_;
+
+    Debug.Log($"[Grass::Debug] Init: density={density_}, extent={extent_meters_}, count={count_}, cell_dim={cell_dim_}, instances={total_instances_}, tex={tex_width_}x{tex_height_}, scale={base_transform_.localScale}, rot={base_transform_.localRotation.eulerAngles}");
+    Debug.Log($"[Grass::Debug] Init details: count_.x={count_.x}, count_.y={count_.y}, count_.z={count_.z}, extent.x={extent_meters_.x}, extent.z={extent_meters_.z}");
+  }
+
+  private bool Valid() {
+    if (prefab_ == null) {
+      Debug.LogError("[Grass::Debug] prefab is null.");
+      return false;
+    }
+    if (mesh_ == null) {
+      Debug.LogError("[Grass::Debug] mesh is null.");
+      return false;
+    }
+    if (instance_material_ == null) {
+      Debug.LogError("[Grass::Debug] instance_material is null.");
+      return false;
+    }
+    if (blit_material_ == null) {
+      Debug.LogError("[Grass::Debug] blit_material is null (failed to generate).");
+      return false;
+    }
+    if (instance_data_tex_ == null) {
+      Debug.LogError("[Grass::Debug] instance_data_tex is null.");
+      return false;
+    }
+    return true;
+  }
+
+  void Start() {
+    Init();
+    if (!Valid()) {
+      return;
+    }
+
+    initialized_ = true;
+    Debug.Log($"[Grass::Debug] GPU mode initialized");
+  }
+
+  void Update() {
+    // Reinitialize if any config changed at runtime.
+    if (density_ != density_live_ ||
+        extent_meters_ != extent_meters_live_ ||
+        angle_randomization_ != angle_randomization_live_ ||
+        scale_randomization_ != scale_randomization_live_) {
+      Init();
+      initialized_ = false;
+    }
+
+    if (!Valid()) {
+      return;
+    }
+
+    VRCPlayerApi lcl_player = Networking.LocalPlayer;
+    Vector3 player_pos = lcl_player.GetPosition();
+    int grid_x = Mathf.FloorToInt(player_pos.x * inv_cell_dim_.x);
+    int grid_y = Mathf.FloorToInt(player_pos.y * inv_cell_dim_.y);
+    int grid_z = Mathf.FloorToInt(player_pos.z * inv_cell_dim_.z);
+
+    int half_x = count_.x / 2;
+    int half_y = count_.y / 2;
+    int half_z = count_.z / 2;
+
+    // Update blit material properties
+    blit_material_.SetVector("_PlayerGridPos", new Vector3(grid_x, grid_y, grid_z));
+    blit_material_.SetVector("_GridCount", new Vector3(count_.x, count_.y, count_.z));
+    blit_material_.SetVector("_GridHalf", new Vector3(half_x, half_y, half_z));
+    blit_material_.SetVector("_TexDimensions", new Vector2(tex_width_, tex_height_));
+
+    // Blit to generate instance data texture
+    VRCGraphics.Blit(null, instance_data_tex_, blit_material_);
+
+    // Update instance material properties
+    instance_material_.SetTexture("_Instance_Texture_Offset_Data_Tex", instance_data_tex_);
+    instance_material_.SetVector("_Instance_Texture_Offset_Cell_Dimensions", cell_dim_);
+    instance_material_.SetVector("_Instance_Texture_Offset_Angle_Randomization", angle_randomization_);
+    instance_material_.SetFloat("_Instance_Texture_Offset_Scale_Randomization", scale_randomization_);
+    instance_material_.SetVector("_Instance_Texture_Offset_Base_Scale", base_transform_.localScale);
+
+    // Pass rotation as quaternion (x, y, z, w)
+    Quaternion rot = base_transform_.localRotation;
+    instance_material_.SetVector("_Instance_Texture_Offset_Base_Rotation", new Vector4(rot.x, rot.y, rot.z, rot.w));
+
+    if (Time.frameCount % 300 == 0) {
+      Debug.Log($"[Grass::Debug] Drawing {total_instances_} GPU instances");
+      Debug.Log($"[Grass::Debug] GridCount={count_}, TexDim={tex_width_}x{tex_height_}, CellDim={cell_dim_}");
+    }
+
+    // Draw instances with identity transforms - GPU handles everything
+    // Must draw tex_width * tex_height instances to match texture
+    VRCGraphics.DrawMeshInstanced(
+        mesh_,
+        0,
+        instance_material_,
+        identity_transforms_,
+        total_instances_,
+        null,
+        UnityEngine.Rendering.ShadowCastingMode.Off,
+        true,
+        0,
+        null,
+        UnityEngine.Rendering.LightProbeUsage.Off,
+        null);
+
+    initialized_ = true;
+  }
+
+  void OnDestroy() {
+    if (instance_data_tex_ != null) {
+      instance_data_tex_.Release();
+    }
+  }
+}
+
+#if UNITY_EDITOR && !COMPILER_UDONSHARP
+[CustomEditor(typeof(InstanceGrass))]
+public class InstanceGrassEditor : Editor
+{
+  public override void OnInspectorGUI()
+  {
+    DrawDefaultInspector();
+
+    InstanceGrass script = (InstanceGrass)target;
+
+    // Auto-generate blit material if missing
+    if (script.blit_material_ == null)
+    {
+      if (GUILayout.Button("Generate Blit Material"))
+      {
+        GenerateBlitMaterial(script);
+      }
+
+      EditorGUILayout.HelpBox("Blit material is missing. Click the button above to auto-generate it.", MessageType.Warning);
+    }
+    else
+    {
+      EditorGUILayout.HelpBox("Blit material is set. GPU instancing ready.", MessageType.Info);
+    }
+  }
+
+  private void GenerateBlitMaterial(InstanceGrass script)
+  {
+    Shader blitShader = Shader.Find("yum_food/GrassGridBlit");
+    if (blitShader == null)
+    {
+      EditorUtility.DisplayDialog("Error", "Could not find shader 'yum_food/GrassGridBlit'. Make sure GrassGridBlit.shader is imported.", "OK");
+      return;
+    }
+
+    string assetPath = "Assets/yum_food/3ner/Grass_Generated/Grass_generated.mat";
+
+    // Create or load existing material
+    Material blitMat = AssetDatabase.LoadAssetAtPath<Material>(assetPath);
+    if (blitMat == null)
+    {
+      // Create new material
+      blitMat = new Material(blitShader);
+      blitMat.name = "Grass_generated";
+
+      // Ensure directory exists
+      string directory = Path.GetDirectoryName(assetPath);
+      if (!Directory.Exists(directory))
+      {
+        Directory.CreateDirectory(directory);
+      }
+
+      AssetDatabase.CreateAsset(blitMat, assetPath);
+      Debug.Log($"[Grass::Editor] Created blit material at {assetPath}");
+    }
+    else
+    {
+      // Update existing material shader
+      blitMat.shader = blitShader;
+      EditorUtility.SetDirty(blitMat);
+      Debug.Log($"[Grass::Editor] Updated existing blit material at {assetPath}");
+    }
+
+    script.blit_material_ = blitMat;
+    EditorUtility.SetDirty(script);
+    AssetDatabase.SaveAssets();
+  }
+
+  [UnityEditor.Callbacks.DidReloadScripts]
+  private static void OnScriptsReloaded()
+  {
+    // Auto-generate blit material for all InstanceGrass components when scripts reload
+    InstanceGrass[] allGrass = FindObjectsOfType<InstanceGrass>();
+    foreach (var grass in allGrass)
+    {
+      if (grass.blit_material_ == null)
+      {
+        var editor = CreateEditor(grass) as InstanceGrassEditor;
+        if (editor != null)
+        {
+          editor.GenerateBlitMaterial(grass);
+          DestroyImmediate(editor);
+        }
+      }
+    }
+  }
+}
+#endif
diff --git a/Scripts/InstanceGrass.cs.meta b/Scripts/InstanceGrass.cs.meta
new file mode 100755
index 0000000..58e03e6
--- /dev/null
+++ b/Scripts/InstanceGrass.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 8dd03d28500e21640aad6c2650091d4c
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/features.cginc b/features.cginc
index ebcf8a7..292e03c 100755
--- a/features.cginc
+++ b/features.cginc
@@ -61,6 +61,10 @@
 #pragma shader_feature_local _INSTANCE_DISTANCE_CULLING
 //endex
 
+//ifex _Instance_Texture_Offset_Enabled==0
+#pragma shader_feature_local _INSTANCE_TEXTURE_OFFSET
+//endex
+
 //ifex _Parallax_Heightmap_Enabled==0
 #pragma shader_feature_local _PARALLAX_HEIGHTMAP
 //endex
diff --git a/globals.cginc b/globals.cginc
index 0341146..9bc4330 100755
--- a/globals.cginc
+++ b/globals.cginc
@@ -170,6 +170,16 @@ float _Ray_Marching_Hexagon_Height;
 float _Instance_Distance_Culling_Distance;
 #endif  // _INSTANCE_DISTANCE_CULLING
 
+#if defined(_INSTANCE_TEXTURE_OFFSET)
+texture2D _Instance_Texture_Offset_Data_Tex;
+float4 _Instance_Texture_Offset_Data_Tex_TexelSize;
+float3 _Instance_Texture_Offset_Cell_Dimensions;
+float3 _Instance_Texture_Offset_Angle_Randomization;
+float _Instance_Texture_Offset_Scale_Randomization;
+float3 _Instance_Texture_Offset_Base_Scale;
+float4 _Instance_Texture_Offset_Base_Rotation;
+#endif  // _INSTANCE_TEXTURE_OFFSET
+
 #if defined(_PARALLAX_HEIGHTMAP)
 texture2D _Parallax_Heightmap;
 float4 _Parallax_Heightmap_ST;
diff --git a/instancing.cginc b/instancing.cginc
index eb8e25b..6672db4 100755
--- a/instancing.cginc
+++ b/instancing.cginc
@@ -4,6 +4,87 @@
 #include "globals.cginc"
 #include "interpolators.cginc"
 
+#if defined(_INSTANCE_TEXTURE_OFFSET)
+
+// Hash function for deterministic pseudo-random values
+// Returns 5 pseudo-random floats in [0,1) from a single hash computation
+void Hash5(int x, int z, out float r0, out float r1, out float r2, out float r3, out float r4) {
+  int h = (x * 73856093) ^ (z * 83492791);
+
+  h = h ^ (h >> 13);
+  h = h * 1274126177;
+  r0 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+
+  h = h ^ (h >> 13);
+  h = h * 1274126177;
+  r1 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+
+  h = h ^ (h >> 13);
+  h = h * 1274126177;
+  r2 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+
+  h = h ^ (h >> 13);
+  h = h * 1274126177;
+  r3 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+
+  h = h ^ (h >> 13);
+  h = h * 1274126177;
+  r4 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+}
+
+// Quaternion multiplication
+float4 qmul(float4 q1, float4 q2) {
+  return float4(
+    q1.w * q2.x + q1.x * q2.w + q1.y * q2.z - q1.z * q2.y,
+    q1.w * q2.y - q1.x * q2.z + q1.y * q2.w + q1.z * q2.x,
+    q1.w * q2.z + q1.x * q2.y - q1.y * q2.x + q1.z * q2.w,
+    q1.w * q2.w - q1.x * q2.x - q1.y * q2.y - q1.z * q2.z
+  );
+}
+
+// Rotate vector by quaternion
+float3 qrotate(float4 q, float3 v) {
+  float3 t = 2 * cross(q.xyz, v);
+  return v + q.w * t + cross(q.xyz, t);
+}
+
+// Create quaternion from Euler angles (in degrees)
+float4 euler_to_quat(float3 euler) {
+  float3 rad = euler * 0.0174533; // deg to rad
+  float3 c = cos(rad * 0.5);
+  float3 s = sin(rad * 0.5);
+
+  return float4(
+    s.x * c.y * c.z - c.x * s.y * s.z,
+    c.x * s.y * c.z + s.x * c.y * s.z,
+    c.x * c.y * s.z - s.x * s.y * c.z,
+    c.x * c.y * c.z + s.x * s.y * s.z
+  );
+}
+
+// Compute rotation quaternion from hash
+float4 compute_rotation(int x, int z) {
+  int h = (x * 73856093) ^ (z * 83492791);
+
+  float r0, r1, r2;
+  h = h ^ (h >> 13); h = h * 1274126177;
+  r0 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+  h = h ^ (h >> 13); h = h * 1274126177;
+  r1 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+  h = h ^ (h >> 13); h = h * 1274126177;
+  r2 = (h & 0x7FFFFFFF) / float(0x7FFFFFFF);
+
+  float3 euler = float3(
+    _Instance_Texture_Offset_Angle_Randomization.x * (r0 * 2.0 - 1.0),
+    _Instance_Texture_Offset_Angle_Randomization.y * (r1 * 2.0 - 1.0),
+    _Instance_Texture_Offset_Angle_Randomization.z * (r2 * 2.0 - 1.0)
+  );
+
+  return euler_to_quat(euler);
+}
+
+#endif  // _INSTANCE_TEXTURE_OFFSET
+
 void instance_distance_culling(inout v2f i) {
 #if defined(_INSTANCE_DISTANCE_CULLING)
   // We want to measure the distance from the instance's transform to the camera.
@@ -15,6 +96,75 @@ void instance_distance_culling(inout v2f i) {
 #endif  // _INSTANCE_DISTANCE_CULLING
 }
 
+void instancing_vert(inout appdata v) {
+#if defined(_INSTANCE_TEXTURE_OFFSET) && defined(UNITY_INSTANCING_ENABLED)
+  // Extract instance ID from the matrix translation component
+  // We encoded it in the X translation (m03) on the CPU side
+  float encodedID = unity_ObjectToWorld[0][3];
+  uint instanceID = (uint)encodedID;
+
+  // Read grid coordinates from instance data texture
+  // _TexelSize.zw contains (width, height)
+  float2 texDimensions = _Instance_Texture_Offset_Data_Tex_TexelSize.zw;
+  int2 texCoord = int2(instanceID % (uint)texDimensions.x,
+                       instanceID / (uint)texDimensions.x);
+  float2 uv = (float2(texCoord) + 0.5) / texDimensions;
+  float4 instanceData = _Instance_Texture_Offset_Data_Tex.SampleLevel(point_repeat_s, uv, 0);
+
+  // Check if this is a valid instance (alpha >= 0)
+  if (instanceData.w < 0) {
+    // Invalid instance - collapse to degenerate triangle far away
+    v.vertex.xyz = float3(0, -100000, 0);
+    return;
+  }
+
+  int3 gridCoord = int3(instanceData.xyz);
+
+  // Compute hash values for randomization
+  float h0, h1, h2, h3, h4;
+  Hash5(gridCoord.x, gridCoord.z, h0, h1, h2, h3, h4);
+
+  // Base grid position
+  float3 basePosition = float3(
+    gridCoord.x * _Instance_Texture_Offset_Cell_Dimensions.x,
+    gridCoord.y * _Instance_Texture_Offset_Cell_Dimensions.y,
+    gridCoord.z * _Instance_Texture_Offset_Cell_Dimensions.z
+  );
+
+  // Add randomized offset within cell
+  float3 positionOffset = float3(
+    _Instance_Texture_Offset_Cell_Dimensions.x * h0,
+    _Instance_Texture_Offset_Cell_Dimensions.y * h1,
+    _Instance_Texture_Offset_Cell_Dimensions.z * h2
+  );
+
+  // Compute random rotation from hash (in world space)
+  float4 randomRotation = compute_rotation(gridCoord.x, gridCoord.z);
+
+  // Combine with base rotation: apply base rotation first, then world-space randomization
+  float4 finalRotation = qmul(randomRotation, _Instance_Texture_Offset_Base_Rotation);
+
+  // Compute scale
+  float3 scale = _Instance_Texture_Offset_Base_Scale * (1.0 + h4 * _Instance_Texture_Offset_Scale_Randomization);
+
+  // Apply transform to vertex in object space
+  float3 scaledVertex = v.vertex.xyz * scale;
+  float3 rotatedVertex = qrotate(finalRotation, scaledVertex);
+  float3 transformedVertex = rotatedVertex + basePosition + positionOffset;
+
+  // Compensate for the encoded offset that Unity will apply via the matrix
+  // Unity will add encodedID to X, so we subtract it here
+  transformedVertex.x -= encodedID;
+
+  // Update vertex position
+  v.vertex.xyz = transformedVertex;
+
+  // Transform normal and tangent (only rotation, no scale - they're direction vectors)
+  v.normal = qrotate(finalRotation, v.normal);
+  v.tangent.xyz = qrotate(finalRotation, v.tangent.xyz);
+#endif  // _INSTANCE_TEXTURE_OFFSET
+}
+
 void instancing_frag(v2f i) {
   instance_distance_culling(i);
 }