Triangle2D

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

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+using UnityEngine;
+using UCL;
+
+// 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;
+    }
+}