math: add BoxIsectBox() method to test interesections.

src/lol/math/geometry.h

@@ -58,6 +58,17 @@ struct Box3D
     vec3 A, B;
 };
 
+static inline bool BoxIsectBox(Box2D const &b1, Box2D const &b2)
+{
+    vec2 c1 = 0.5f * (b1.A + b1.B);
+    vec2 c2 = 0.5f * (b2.A + b2.B);
+    vec2 e1 = 0.5f * (b1.B - b1.A);
+    vec2 e2 = 0.5f * (b2.B - b2.A);
+
+    return abs(c1.x - c2.x) < abs(e1.x) + abs(e2.x)
+        || abs(c1.y - c2.y) < abs(e1.y) + abs(e2.y);
+}
+
 bool TriangleIsectTriangle(vec3 const &v00, vec3 const &v01, vec3 const &v02,
                            vec3 const &v10, vec3 const &v11, vec3 const &v12,
                            vec3 &iP00, vec3 &iP10);