Triangle2D

Assets/Scripts/2D/Geometry/Triangle2D.cs

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+using UnityEngine;
+
+namespace UnityLibrary
+{
+    // if you need to run collision checks within a triangular area, the easiest
+    // way to do that in Unity is to use a polygon collider.  this is not very
+    // performant.  this class allows you to run those collision checks without
+    // the performance overhead.
+
+    public class Triangle2D
+    {
+        Vector2[] vertices = new Vector2[3];
+
+        public Triangle2D(Vector2 v1, Vector2 v2, Vector2 v3) 
+        {
+            Update(v1, v2, v3);
+        }
+
+        // update triangle by defining all its vertices
+        public void Update(Vector2 v1, Vector2 v2, Vector2 v3) 
+        {
+            vertices[0] = v1;
+            vertices[1] = v2;
+            vertices[2] = v3;
+        }
+
+        // update triangle by redefining its origin (remaining points update relative to that)
+        public void Update(Vector2 v1) 
+        {
+            Vector2 delta = v1 - vertices[0];
+            vertices[0] = v1;
+            vertices[1] += delta;
+            vertices[2] += delta;
+        }
+
+        // update triangle with rotation and pivot point
+        public void Update(Vector2 v1, Vector2 v2, Vector2 v3, float rotation, Vector2 pivot) 
+        {
+            vertices[0] = v1.Rotate(rotation, pivot);
+            vertices[1] = v2.Rotate(rotation, pivot);
+            vertices[2] = v3.Rotate(rotation, pivot);
+        }
+
+        float Sign(Vector2 p1, Vector2 p2, Vector2 p3) 
+        {
+            return (p1.x - p3.x) * (p2.y - p3.y) - (p2.x - p3.x) * (p1.y - p3.y);
+        }
+
+        public bool Contains(Vector2 pt, bool debug = false) 
+        {
+            float d1, d2, d3;
+            bool has_neg, has_pos;
+
+            d1 = Sign(pt, vertices[0], vertices[1]);
+            d2 = Sign(pt, vertices[1], vertices[2]);
+            d3 = Sign(pt, vertices[2], vertices[0]);
+
+            has_neg = (d1 < 0) || (d2 < 0) || (d3 < 0);
+            has_pos = (d1 > 0) || (d2 > 0) || (d3 > 0);
+
+            bool contains = ! (has_neg && has_pos);
+
+            return contains;
+        }
+    }
+}
+

Assets/Scripts/Extensions/Vector2Extensions.cs

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+using UnityEngine;
+
+namespace UnityLibrary
+{
+    static class Vector2Extensions
+    {
+        public static Vector2 Round(this Vector2 vector, int to = 0) => new Vector2(vector.x.Round(to), vector.y.Round(to)); 
+
+        public static Vector2 Rotate(this Vector2 vector, float angle, Vector2 pivot = default(Vector2)) 
+        {
+            Vector2 rotated = Quaternion.Euler(new Vector3(0f, 0f, angle)) * (vector - pivot);
+            return rotated + pivot;
+        }
+    }
+}