Thanks for the contribution

Merged in release (pull request #88)

Add squircle primitive

Approved-by: Simon Jackson

Editor/UIExtensionsMenuOptions.cs

@@ -1208,6 +1208,14 @@ namespace UnityEditor.UI
 			Selection.activeGameObject = go;
 		}
 
+        [MenuItem("GameObject/UI/Extensions/Primitives/UI Squircle", false)]
+		static public void AddUISquircle(MenuCommand menuCommand)
+		{
+			GameObject go = CreateUIElementRoot("UI Squircle", menuCommand, s_ImageGUIElementSize);
+			go.AddComponent<UISquircle>();
+			Selection.activeGameObject = go;
+		}
+
 		[MenuItem("GameObject/UI/Extensions/Primitives/UI Circle", false)]
 		static public void AddUICircle(MenuCommand menuCommand)
 		{

Runtime/Scripts/Primitives/UISquircle.cs

@@ -0,0 +1,140 @@
+/// Credit Soprachev Andrei
+
+using System.Collections.Generic;
+using System.Linq;
+using UnityEditor;
+
+
+namespace UnityEngine.UI.Extensions
+{
+    [AddComponentMenu("UI/Extensions/Primitives/Squircle")]
+    public class UISquircle : UIPrimitiveBase
+    {
+        const float C = 1.0f;
+        public enum Type
+        {
+            Classic,
+            Scaled
+        }
+
+        [Space]
+        public Type squircleType = Type.Scaled;
+        [Range(1, 40)]
+        public float n = 4;
+        [Min(0.1f)]
+        public float delta = 5f;
+        public float quality = 0.1f;
+        [Min(0)]
+        public float radius = 1000;
+
+
+        private float a, b;
+        private List<Vector2> vert = new List<Vector2>();
+
+
+        private float SquircleFunc(float t, bool xByY)
+        {
+            if (xByY)
+                return (float)System.Math.Pow(C - System.Math.Pow(t / a, n), 1f / n) * b;
+
+            return (float)System.Math.Pow(C - System.Math.Pow(t / b, n), 1f / n) * a;
+        }
+
+        protected override void OnPopulateMesh(VertexHelper vh)
+        {
+
+            float dx = 0;
+            float dy = 0;
+
+            float width = rectTransform.rect.width / 2;
+            float height = rectTransform.rect.height / 2;
+
+            if (squircleType == Type.Classic)
+            {
+                a = width;
+                b = height;
+            }
+            else
+            {
+                a = Mathf.Min(width, height, radius);
+                b = a;
+
+                dx = width - a;
+                dy = height - a;
+            }
+
+
+
+            float x = 0;
+            float y = 1;
+            vert.Clear();
+            vert.Add(new Vector2(0, height));
+            while (x < y)
+            {
+                y = SquircleFunc(x, true);
+                vert.Add(new Vector2(dx + x, dy + y));
+                x += delta;
+            }
+
+            if (float.IsNaN(vert.Last().y))
+            {
+                vert.RemoveAt(vert.Count - 1);
+            }
+
+            while (y > 0)
+            {
+                x = SquircleFunc(y, false);
+                vert.Add(new Vector2(dx + x, dy + y));
+                y -= delta;
+            }
+
+            vert.Add(new Vector2(width, 0));
+
+            for (int i = 1; i < vert.Count - 1; i++)
+            {
+                if (vert[i].x < vert[i].y)
+                {
+                    if (vert[i - 1].y - vert[i].y < quality)
+                    {
+                        vert.RemoveAt(i);
+                        i -= 1;
+                    }
+                }
+                else
+                {
+                    if (vert[i].x - vert[i - 1].x < quality)
+                    {
+                        vert.RemoveAt(i);
+                        i -= 1;
+                    }
+                }
+            }
+
+            vert.AddRange(vert.AsEnumerable().Reverse().Select(t => new Vector2(t.x, -t.y)));
+            vert.AddRange(vert.AsEnumerable().Reverse().Select(t => new Vector2(-t.x, t.y)));
+
+            vh.Clear();
+
+            for (int i = 0; i < vert.Count - 1; i++)
+            {
+                vh.AddVert(vert[i], color, Vector2.zero);
+                vh.AddVert(vert[i + 1], color, Vector2.zero);
+                vh.AddVert(Vector2.zero, color, Vector2.zero);
+
+                vh.AddTriangle(i * 3, i * 3 + 1, i * 3 + 2);
+            }
+        }
+
+        [CustomEditor(typeof(UISquircle))]
+        public class UISquircleEditor : Editor
+        {
+            public override void OnInspectorGUI()
+            {
+                DrawDefaultInspector();
+                UISquircle script = (UISquircle)target;
+                GUILayout.Label("Vertex count: " + script.vert.Count().ToString());
+            }
+        }
+
+    }
+}

Runtime/Scripts/Primitives/UISquircle.cs.meta

@@ -0,0 +1,11 @@
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