1 files changed, 56 insertions, 0 deletions
diff --git a/src/main/scala/sims/geometry/ConvexPolygon.scala b/src/main/scala/sims/geometry/ConvexPolygon.scala
new file mode 100644
index 0000000..bfd17a1
--- /dev/null
+++ b/src/main/scala/sims/geometry/ConvexPolygon.scala
@@ -0,0 +1,56 @@
+/*
+ * Simple Mechanics Simulator (SiMS)
+ * copyright (c) 2009 Jakob Odersky
+ * made available under the MIT License
+*/
+
+package sims.geometry
+
+import sims.collision._
+import sims.geometry._
+
+/**Common properties of all convex polygons.*/
+trait ConvexPolygon {
+  
+  /**Returns positions of all vertices of this Polygon. Vertices are ordered counter-clockwise.
+   * @return position vectors of the vertices*/
+  def vertices: Seq[Vector2D]
+  
+  /**Returns all sides of this polygon. The sides are ordered counter-clockwise, the first vertex of the side
+   * giving the side index.*/
+  def sides = (for (i <- 0 until vertices.length) yield (new Segment(vertices(i), vertices((i + 1) % vertices.length)))).toArray
+  
+  /**Returns the projection of this polygon onto the line given by the directional vector <code>axis</code>.
+   * @param axis directional vector of the line
+   * @return projection of this polygon*/
+  def project(axis: Vector2D) = {
+    val points = for (v <- vertices) yield {v project axis}
+    val bounds = for (p <- points) yield {if (axis.x != 0) p.x / axis.x else p.y / axis.y}
+    Projection(axis,
+              (bounds(0) /: bounds)(math.min(_,_)),
+              (bounds(0) /: bounds)(math.max(_,_)))
+  }
+  
+  /**Returns this polygon's axis aligned bounding box.
+   * @see collision.AABB*/
+  def AABB = {
+    val xs = vertices map (_.x)
+    val ys = vertices map (_.y)
+    new AABB(Vector2D(xs.min, ys.min),
+             Vector2D(xs.max, ys.max))
+  }
+  
+  /**Checks if the point <code>point</code> is contained in this polygon.
+   * <p>
+   * A ray is created, originating from the point and following an arbitrary direction (X-Axis was chosen).
+   * The number of intersections between the ray and this polygon's sides (including vertices) is counted.
+   * The amount of intersections with vertices is substracted form the previuos number.
+   * If the latter number is odd, the point is contained in the polygon.*/
+  def contains(point: Vector2D) = {
+    val r = new Ray(point, Vector2D.i)
+    var intersections = 0
+    for (s <- sides; if (r intersects s)) intersections += 1
+    for (v <- vertices; if (r contains v)) intersections -= 1
+    intersections % 2 != 0
+  }
+}