1 files changed, 72 insertions, 0 deletions
diff --git a/src/main/scala/sims/geometry/Segment.scala b/src/main/scala/sims/geometry/Segment.scala
new file mode 100644
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+++ b/src/main/scala/sims/geometry/Segment.scala
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+/*
+ * Simple Mechanics Simulator (SiMS)
+ * copyright (c) 2009 Jakob Odersky
+ * made available under the MIT License
+*/
+
+package sims.geometry
+
+/**A segment is given by its vertices.
+ * @param vertex1 position vector of the first vertex
+ * @param vertex2 position vector of the second vertex
+ * @throws IllegalArgumentException if both vertices are equal
+ */
+case class Segment(vertex1: Vector2D, vertex2: Vector2D){
+  require(vertex1 != vertex2, "A segment must have 2 distinct vertices!")
+  
+  /**Length of this segment.*/
+  val length = (vertex2 - vertex1).length
+  
+  /**Vector from <code>vertex1</code> to <code>vertex2</code>.*/
+  val d = vertex2 - vertex1
+  
+  /**Unit directional vector.*/
+  val d0 = d.unit
+  
+  /**Right normal vector.*/
+  val n = d.rightNormal
+  
+  /**Right normal unit vector.*/
+  val n0 = n.unit
+  
+  /**Smallest distance between this segment and the point <code>point</code>.*/
+  def distance(point: Vector2D): Double = {
+    val v = point - vertex1	//vector from vertex1 to point
+    val projection = v project d
+    val alpha = if (d.x != 0) d.x / projection.x else d.y / projection.y
+    if (alpha >= 0 && projection.length <= length)	//point is closer to line between vertex1 and vertex2
+      (v project n0).length
+    else if (alpha < 0)	//point is closer to vertex1
+      (point - vertex1).length
+    else if (alpha > 0)	//point is closer to vertex2
+       (point - vertex2).length
+       else
+         throw new IllegalArgumentException("Error occured trying to compute distance between segment and point.")
+  }
+  
+  def clipToSegment(s: Segment): Option[Vector2D] = {
+    
+    val distance1 = (vertex1 - s.vertex1) dot s.n0
+    val distance2 = (vertex2 - s.vertex1)  dot s.n0
+    
+    if (distance1 * distance2 < 0) { //auf anderen Seiten
+      /* Geradengleichungen
+       * ==================
+       * Segment1:	s1: x = a + alpha * r | alpha in [0,1]
+       * Segment2:	s2: x = b + beta * s | beta in [0,1]
+       * 
+       * alpha = [s2(a1-b1)-s1(a2-b2)] / [r2s1-r1s2]
+       * beta = [r2(b1-a1)-r1(b2-a2)] / [r1s2-r2s1]
+       *      = [r1(b2-a2)]-r2(b1-a1) / [r2s1-r1s2]
+       * s1: vertex1 + alpha * d
+       * s2: s.vertex1 + beta * s.d
+       */
+      val denom: Double = d.y * s.d.x - d.x * s.d.y 
+      val alpha: Double = (s.d.y * (vertex1.x - s.vertex1.x) - s.d.x * (vertex1.y - s.vertex1.y)) / denom
+      val beta: Double = (d.x * (s.vertex1.y - vertex1.y) - d.y * (s.vertex1.x - vertex1.x)) / denom
+      if (0.0 <= alpha && alpha <= 1.0 && 0.0 <= beta && beta <= 1.0) Some(vertex1 + d * alpha)
+      else None
+    }
+    else None
+  }
+}