From 9d20024aa35cd7f923ebfc1ed9a2ffbf2731da70 Mon Sep 17 00:00:00 2001
From: Jakob Odersky <jodersky@gmail.com>
Date: Thu, 5 Nov 2009 21:02:40 +0000
Subject: Initial import.

---
 src/sims/dynamics/joints/DistanceJoint.scala | 76 ++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 src/sims/dynamics/joints/DistanceJoint.scala

(limited to 'src/sims/dynamics/joints/DistanceJoint.scala')

diff --git a/src/sims/dynamics/joints/DistanceJoint.scala b/src/sims/dynamics/joints/DistanceJoint.scala
new file mode 100644
index 0000000..2d5633f
--- /dev/null
+++ b/src/sims/dynamics/joints/DistanceJoint.scala
@@ -0,0 +1,76 @@
+/*
+ * Simple Mechanics Simulator (SiMS)
+ * copyright (c) 2009 Jakob Odersky
+ * made available under the MIT License
+*/
+
+package sims.dynamics.joints
+
+import sims.geometry._
+
+/** DistanceJoints halten die Bindungspunkte auf ihren Bindungskoerpern bei einem konstanten Abstand.
+ * @param node1 erster Koerper der Verbindung
+ * @param anchor1 Bindungspunkt auf Koerper eins
+ * @param node2 zweiter Koerper der Verbindung
+ * @param anchor2 Bindungspunkt auf Koerper zwei*/
+case class DistanceJoint(node1: Body, anchor1: Vector2D, node2: Body, anchor2: Vector2D) extends  Joint{
+  def this(node1: Body, node2: Body) = this(node1, node1.pos, node2, node2.pos)
+  
+  /**Abstand der beiden Bindungspunkte bei initialisierung (der gewollte Abstand).*/
+  val distance = (anchor2 - anchor1).length
+  
+  private val a1 = anchor1 - node1.pos
+  private val a2 = anchor2 - node2.pos
+  private val initRotation1 = node1.rotation
+  private val initRotation2 = node2.rotation
+  
+  /**Ergibt den Bindungspunkt auf Koerper eins.*/
+  def connection1 = (a1 rotate (node1.rotation - initRotation1)) + node1.pos
+  
+  /**Ergibt den Bindungspunkt auf Koerper zwei.*/
+  def connection2 = (a2 rotate (node2.rotation - initRotation2)) + node2.pos
+  
+  /**Relative Position der Bindungspunkte.*/
+  def x = connection2 - connection1
+  
+  /**Relative Geschwindigkeit der Bindungspunkte.*/
+  def v = node2.velocityOfPoint(connection2) - node1.velocityOfPoint(connection1)
+  
+  /* x = connection2 - connection1
+     * C = ||x|| - L
+     * u = x / ||x||
+     * v = v2 + w2 cross r2 - v1 - w1 cross r1
+     * Cdot = u dot v
+     * J = [-u	-(r1 cross u)	u	(r2 cross u)]
+     * 1/m = J * M^-1 * JT
+     * = 1/m1 * u * u + 1/m2 * u * u + 1/I1 * (r1 cross u)^2 + 1/I2 * (r2 cross u)^2*/
+  override def correctVelocity(h: Double) = {
+    val x = this.x	//relativer Abstand
+    val v = this.v	//relative Geschwindigkeit
+    val r1 = (connection1 - node1.pos)	//Abstand Punkt-Schwerpunkt, Koerper 1
+    val r2 = (connection2 - node2.pos)	//Abstand Punkt-Schwerpunkt, Koerper 2
+    val cr1 = r1 cross x.unit	//Kreuzprodukt
+    val cr2 = r2 cross x.unit	//Kreuzprodukt
+    val Cdot = x.unit dot v	//Velocity-Constraint
+    val invMass = 1/node1.mass + 1/node1.I * cr1 * cr1 + 1/node2.mass + 1/node2.I * cr2 * cr2	//=J M^-1 JT
+    val m = if (invMass == 0.0) 0.0 else 1/invMass	//Test um Nulldivision zu vermeiden
+    val lambda = -m * Cdot	//=-JV/JM^-1JT
+    val impulse = x.unit * lambda	//P=J lambda
+    node1.applyImpulse(-impulse, connection1)
+    node2.applyImpulse(impulse, connection2) 
+  }
+  
+  override def correctPosition(h: Double) = {
+    val C = x.length - distance
+    val cr1 = (connection1 - node1.pos) cross x.unit
+    val cr2 = (connection2 - node2.pos) cross x.unit
+    val invMass = 1/node1.mass + 1/node1.I * cr1 * cr1 + 1/node2.mass + 1/node2.I * cr2 * cr2
+    val m = if (invMass == 0.0) 0.0 else 1/invMass
+    val impulse = -x.unit * m * C
+    node1.pos -= impulse / node1.mass
+    node2.pos += impulse / node2.mass
+    node1.rotation -= ((connection1 - node1.pos) cross impulse) / node1.I
+    node2.rotation += ((connection2 - node2.pos) cross impulse) / node2.I
+  }
+  
+}
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