Sagging

Assets/Scenes/SampleScene.unity

@@ -156,8 +156,8 @@ MonoBehaviour:
   material: {fileID: 2100000, guid: 8f3914ac4291e664ba60ae208ae66460, type: 2}
   gradientA:
     serializedVersion: 2
-    key0: {r: 1, g: 1, b: 1, a: 0.3137255}
+    key0: {r: 0.764151, g: 0.18413278, b: 0, a: 0.3137255}
-    key1: {r: 1, g: 0, b: 0, a: 0.3529412}
+    key1: {r: 1, g: 1, b: 0, a: 0.3529412}
     key2: {r: 0, g: 0, b: 0, a: 0}
     key3: {r: 0, g: 0, b: 0, a: 0}
     key4: {r: 0, g: 0, b: 0, a: 0}
@@ -165,7 +165,7 @@ MonoBehaviour:
     key6: {r: 0, g: 0, b: 0, a: 0}
     key7: {r: 0, g: 0, b: 0, a: 0}
     ctime0: 0
-    ctime1: 32768
+    ctime1: 65535
     ctime2: 65535
     ctime3: 0
     ctime4: 0
@@ -181,12 +181,12 @@ MonoBehaviour:
     atime6: 0
     atime7: 0
     m_Mode: 0
-    m_NumColorKeys: 3
+    m_NumColorKeys: 2
     m_NumAlphaKeys: 2
   gradientB:
     serializedVersion: 2
-    key0: {r: 0, g: 0, b: 1, a: 0.54901963}
+    key0: {r: 0.40392157, g: 0.14109339, b: 0, a: 0.54901963}
-    key1: {r: 1, g: 1, b: 1, a: 0.627451}
+    key1: {r: 0, g: 0.6320754, b: 0, a: 0.627451}
     key2: {r: 1, g: 1, b: 0, a: 0}
     key3: {r: 0, g: 0, b: 0, a: 0}
     key4: {r: 0, g: 0, b: 0, a: 0}
@@ -194,7 +194,7 @@ MonoBehaviour:
     key6: {r: 0, g: 0, b: 0, a: 0}
     key7: {r: 0, g: 0, b: 0, a: 0}
     ctime0: 0
-    ctime1: 32768
+    ctime1: 65535
     ctime2: 65535
     ctime3: 0
     ctime4: 0
@@ -210,10 +210,12 @@ MonoBehaviour:
     atime6: 0
     atime7: 0
     m_Mode: 0
-    m_NumColorKeys: 3
+    m_NumColorKeys: 2
     m_NumAlphaKeys: 2
   leafColorA: {r: 0.45882356, g: 0.97647065, b: 0.29803923, a: 0.49803922}
   leafColorB: {r: 0.21568629, g: 0.4901961, b: 0.13333334, a: 0.9019608}
+  maxSagAngleA: 15
+  maxSagAngleB: 25
 --- !u!4 &197491476
 Transform:
   m_ObjectHideFlags: 0
@@ -221,13 +223,13 @@ Transform:
   m_PrefabInstance: {fileID: 0}
   m_PrefabAsset: {fileID: 0}
   m_GameObject: {fileID: 197491472}
-  m_LocalRotation: {x: 0, y: 0, z: 0, w: 1}
+  m_LocalRotation: {x: 0, y: 0, z: 0.17364816, w: 0.9848078}
   m_LocalPosition: {x: 0, y: 0, z: 0}
   m_LocalScale: {x: 1, y: 1, z: 1}
   m_Children: []
   m_Father: {fileID: 0}
   m_RootOrder: 4
-  m_LocalEulerAnglesHint: {x: 0, y: 0, z: 0}
+  m_LocalEulerAnglesHint: {x: 0, y: 0, z: 20}
 --- !u!1 &705507993
 GameObject:
   m_ObjectHideFlags: 0

Assets/Script/Fractal.cs

@@ -29,12 +29,32 @@ public class Fractal : MonoBehaviour
             var parent = parents[i / 5];
             var part = parts[i];
             part.spinAngle += spinAngleDelta;
-            part.worldRotation = mul(parent.worldRotation,
+
+            float3 upAxis =
+                mul(mul(parent.worldRotation, part.rotation), up());
+            float3 sagAxis = cross(up(), upAxis);
+
+            float sagMagnitude = length(sagAxis);
+            quaternion baseRotation;
+            if (sagMagnitude > 0f)
+            {
+                sagAxis /= sagMagnitude;
+                quaternion sagRotation =
+                    quaternion.AxisAngle(sagAxis, part.maxSagAngle * sagMagnitude);
+                baseRotation = mul(sagRotation, parent.worldRotation);
+            }
+            else
+            {
+                baseRotation = parent.worldRotation;
+            }
+
+            part.worldRotation = mul(baseRotation,
                 mul(part.rotation, quaternion.RotateY(part.spinAngle))
             );
+
             part.worldPosition =
                 parent.worldPosition +
-                mul(parent.worldRotation, 1.5f * scale * part.direction);
+                mul(part.worldRotation, float3(0f, 1.5f * scale, 0f));
             parts[i] = part;
 
             float3x3 r = float3x3(part.worldRotation) * scale;
@@ -44,8 +64,9 @@ public class Fractal : MonoBehaviour
 
     private struct FractalPart
     {
-        public float3 direction, worldPosition;
+        public float3 worldPosition;
         public quaternion rotation, worldRotation;
+        public float maxSagAngle;
         public float spinAngle;
     }
 
@@ -77,6 +98,12 @@ public class Fractal : MonoBehaviour
     [SerializeField]
     Color leafColorB = default;
 
+    [SerializeField, Range(0f, 90f)]
+    float maxSagAngleA = 15f;
+        
+    [SerializeField, Range(0f, 90f)]
+    float maxSagAngleB = 25f;
+
     static float3[] directions =
     {
         up(), right(), left(), forward(), back()
@@ -93,7 +120,7 @@ public class Fractal : MonoBehaviour
     {
         return new FractalPart()
         {
-            direction = directions[childIndex],
+            maxSagAngle = radians(Random.Range(maxSagAngleA, maxSagAngleB)),
             rotation = rotations[childIndex]
         };
     }