Procedural Drawing

Assets/Script/Fractal.cs

@@ -4,13 +4,15 @@ public class Fractal : MonoBehaviour
 {
     private struct FractalPart
     {
-        public Vector3 direction;
-        public Quaternion rotation;
-        public Transform transform;
+        public Vector3 direction, worldPosition;
+        public Quaternion rotation, worldRotation;
+        public float spinAngle;
     }
 
     FractalPart[][] parts;
 
+    Matrix4x4[][] matrices;
+
     [SerializeField, Range(1, 8)]
     int depth = 4;
 
@@ -38,72 +40,120 @@ public class Fractal : MonoBehaviour
         Quaternion.Euler(-90f, 0f, 0f)
     };
     
-    private FractalPart CreatePart(int levelIndex, int childIndex, float scale)
+    private FractalPart CreatePart(int childIndex)
     {
-        var go = new GameObject("Fractal Part L" + levelIndex + " C" + childIndex);
-        go.transform.localScale = scale * Vector3.one;
-        go.transform.SetParent(transform, false);
-        go.AddComponent<MeshFilter>().mesh = mesh;
-        go.AddComponent<MeshRenderer>().material = material;
-
         return new FractalPart()
         {
             direction = directions[childIndex],
-            rotation = rotations[childIndex],
-            transform = go.transform
+            rotation = rotations[childIndex]
         };
     }
 
-    private void Awake()
+    ComputeBuffer[] matricesBuffers;
+
+    static readonly int matricesId = Shader.PropertyToID("_Matrices");
+
+    static MaterialPropertyBlock propertyBlock;
+
+    private void OnEnable()
     {
         parts = new FractalPart[depth][];
+        matrices = new Matrix4x4[depth][];
+        matricesBuffers = new ComputeBuffer[depth];
+        int stride = 16 * 4;
         for (int i = 0, length = 1; i < parts.Length; i++, length *= 5)
         {
             parts[i] = new FractalPart[length];
+            matrices[i] = new Matrix4x4[length];
+            matricesBuffers[i] = new ComputeBuffer(length, stride);
         }
-
-        var scale = 1f;
-        parts[0][0] = CreatePart(0, 0, scale);
+        
+        parts[0][0] = CreatePart(0);
         for (int li = 1; li < parts.Length; li++)
         {
-            scale *= 0.5f;
             FractalPart[] levelParts = parts[li];
             for (int fpi = 0; fpi < levelParts.Length; fpi += 5)
             {
                 for (int ci = 0; ci < 5; ci++)
                 {
-                    levelParts[fpi + ci] = CreatePart(li, ci, scale);
+                    levelParts[fpi + ci] = CreatePart(ci);
                 }
             }
         }
+
+        if (propertyBlock == null)
+        {
+            propertyBlock = new MaterialPropertyBlock();
+        }
+    }
+
+    private void OnDisable()
+    {
+        for (int i = 0; i < matricesBuffers.Length; i++)
+        {
+            matricesBuffers[i].Release();
+        }
+        parts = null;
+        matrices = null;
+        matricesBuffers = null;
+    }
+
+    void OnValidate()
+    {
+        if (parts != null && enabled)
+        {
+            OnDisable();
+            OnEnable();
+        }
     }
 
     private void Update()
     {
-        Quaternion deltaRotation = Quaternion.Euler(0f, 22.5f * Time.deltaTime, 0f);
-
+        float spinAngleDelta = 22.5f * Time.deltaTime;
         FractalPart rootPart = parts[0][0];
-        rootPart.rotation *= deltaRotation;
-        rootPart.transform.localRotation = rootPart.rotation;
+        rootPart.spinAngle += spinAngleDelta;
+        rootPart.worldRotation =
+            transform.rotation *
+            (rootPart.rotation * Quaternion.Euler(0f, rootPart.spinAngle, 0f));
+        rootPart.worldPosition = transform.position;
         parts[0][0] = rootPart;
+        float objectScale = transform.lossyScale.x;
+        matrices[0][0] = Matrix4x4.TRS(
+            rootPart.worldPosition, rootPart.worldRotation, objectScale * Vector3.one
+        );
 
+        float scale = objectScale;
         for (int li = 1; li < parts.Length; li++)
         {
+            scale *= 0.5f;
             FractalPart[] parentParts = parts[li - 1];
             FractalPart[] levelParts = parts[li];
+            Matrix4x4[] levelMatrices = matrices[li];
             for (int fpi = 0; fpi < levelParts.Length; fpi++)
             {
-                var parentTransform = parentParts[fpi / 5].transform;
+                var parent = parentParts[fpi / 5];
                 var part = levelParts[fpi];
-                part.rotation *= deltaRotation;
-                part.transform.rotation = 
-                    parentTransform.localRotation * part.rotation;
-                part.transform.localPosition =
-                    parentTransform.localPosition +
-                    parentTransform.localRotation *
-                    (1.5f * part.transform.localScale.x * part.direction);
+                part.spinAngle += spinAngleDelta;
+				part.worldRotation =
+					parent.worldRotation *
+					(part.rotation * Quaternion.Euler(0f, part.spinAngle, 0f));
+                part.worldPosition =
+                    parent.worldPosition +
+                    parent.worldRotation * (1.5f * scale * part.direction);
                 levelParts[fpi] = part;
+                levelMatrices[fpi] = Matrix4x4.TRS(
+                    part.worldPosition, part.worldRotation, scale * Vector3.one
+                );
             }
         }
+
+        var bounds = new Bounds(rootPart.worldPosition, 3f * objectScale * Vector3.one);
+        for (int i = 0; i < matricesBuffers.Length; i++)
+        {
+            ComputeBuffer buffer = matricesBuffers[i];
+            buffer.SetData(matrices[i]);
+            propertyBlock.SetBuffer(matricesId, buffer);
+            Graphics.DrawMeshInstancedProcedural(mesh, 0, material, bounds, buffer.count, propertyBlock);
+        }
     }
 }

Assets/Script/PartGPU.hlsl

@@ -0,0 +1,17 @@
+#if defined(UNITY_PROCEDURAL_INSTANCING_ENABLED)
+	StructuredBuffer<float4x4> _Matrices;
+#endif
+
+void ConfigureProcedural () {
+	#if defined(UNITY_PROCEDURAL_INSTANCING_ENABLED)
+		unity_ObjectToWorld = _Matrices[unity_InstanceID];
+	#endif
+}
+
+void ShaderGraphFunction_float (float3 In, out float3 Out) {
+	Out = In;
+}
+
+void ShaderGraphFunction_half (half3 In, out half3 Out) {
+	Out = In;
+}

Assets/Script/PartGPU.hlsl.meta

@@ -0,0 +1,9 @@
+fileFormatVersion: 2
+guid: 0ed85852d1001bf44b1fef32640df23b
+ShaderImporter:
+  externalObjects: {}
+  defaultTextures: []
+  nonModifiableTextures: []
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: