1 files changed, 49 insertions, 0 deletions
diff --git a/src/main/scala/sims/geometry/Ray.scala b/src/main/scala/sims/geometry/Ray.scala
new file mode 100644
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+++ b/src/main/scala/sims/geometry/Ray.scala
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+/*
+ * Simple Mechanics Simulator (SiMS)
+ * copyright (c) 2009 Jakob Odersky
+ * made available under the MIT License
+*/
+
+package sims.geometry
+
+import sims.math._
+import scala.math._
+
+/**A ray.
+ * @param point a point on the ray
+ * @param direction this ray's directional vector
+ * @throws IllegalArgumentException if the directional vector is the null vector*/
+case class Ray(point: Vector2D, direction: Vector2D) {
+  
+  require(direction != Vector2D.Null, "A ray's direction cannot be given by a null vector!")
+  
+  /**Checks this ray and the given segment for intersection.
+   * @param s the segment to test for intersection*/
+  def intersects(s: Segment) = {
+    val p1 = point
+    val p2 = point + direction
+    val p3 = s.vertex1
+    val p4 = s.vertex2
+    val d = (p4.y - p3.y) * (p2.x - p1.x) - (p4.x - p3.x) * (p2.y - p1.y)
+    val na = (p4.x - p3.x) * (p1.y - p3.y) - (p4.y - p3.y) * (p1.x - p3.x)
+    val nb = (p2.x - p1.x) * (p1.y - p3.y) - (p2.y - p1.y) * (p1.x - p3.x)
+    if (d == 0 && na == 0 && nb == 0)
+      true //lines are coincident
+    else if (d == 0)
+      false //parallel
+    else {
+      val ua = na / d
+      val ub = nb / d
+      (ub >= 0) && (ub <= 1) && (ua >= 0)
+    }
+  }
+  
+  /**Checks if this ray contains the point <code>p</code>.*/
+  def contains(p: Vector2D) = {
+    val v = p - point
+    p == point ||
+    Matrix22(direction, v).det == 0 &&
+    signum(direction.x) == signum(v.x) &&
+    signum(direction.y) == signum(v.y)
+  }
+}