6 files changed, 90 insertions, 13 deletions
diff --git a/src/tesseract/TesseractUI.java b/src/tesseract/TesseractUI.java
index 99b2fa4..e7749b5 100644
--- a/src/tesseract/TesseractUI.java
+++ b/src/tesseract/TesseractUI.java
@@ -96,18 +96,11 @@ public class TesseractUI extends JFrame {
 	private Timer myTimer;
 	
 	/**
-	 * The gravity of the world
-	 */
-	private Gravity my_gravity;
-	
-	/**
 	 * UI Constructor.
 	 */
 	public TesseractUI() {
 		super("Tesseract Project");
-		
-		my_gravity = new Gravity();
-		
+
 		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
 		
 		myWorld = new World(
@@ -166,6 +159,14 @@ public class TesseractUI extends JFrame {
 		});
 		simulationMenu.add(runSim);
 		
+		JMenuItem resetSim = new JCheckBoxMenuItem("Reset Simulator", true);
+		runSim.addActionListener(new ActionListener() {
+			public void actionPerformed(final ActionEvent e) {
+				myWorld.resetWorld();
+			}
+		});
+		simulationMenu.add(resetSim);
+		
 		//Objects
 		JMenu objectsMenu = new JMenu("Add Object");
 		for (JMenuItem item : myObjectMenuItems) {
@@ -177,11 +178,18 @@ public class TesseractUI extends JFrame {
 		JMenu forcesMenu = new JMenu("Add Forces");
 		JMenuItem gravity = new JCheckBoxMenuItem("Gravity", false);
 		gravity.addActionListener(new ActionListener() {
+				private Force me;
+				
+				// Constructor 
+				{
+					me = new Gravity();
+				}
+				
 				public void actionPerformed(ActionEvent e) {
 					if (((JCheckBoxMenuItem) e.getSource()).isSelected()) {
-						myWorld.addForce(my_gravity);
+						myWorld.addForce(me);
 					} else {
-						myWorld.addForce(my_gravity = new Gravity(-.5f));
+						myWorld.removeForce(me);
 					}
 				}			
 			});
diff --git a/src/tesseract/World.java b/src/tesseract/World.java
index 7bfe0a6..9b43b87 100644
--- a/src/tesseract/World.java
+++ b/src/tesseract/World.java
@@ -21,6 +21,8 @@ import javax.vecmath.Vector3f;
 import tesseract.forces.Force;
 import tesseract.objects.PhysicalObject;
 
+import tesseract.objects.HalfSpace;
+
 import com.sun.j3d.utils.picking.PickTool;
 import com.sun.j3d.utils.picking.behaviors.PickTranslateBehavior;
 import com.sun.j3d.utils.picking.behaviors.PickZoomBehavior;
@@ -101,6 +103,7 @@ public class World {
 		//myScene.addChild(myPickableObjects);
 		
 		addLights();
+		addHalfspaces();
 		
 		myScene.compile();
 	}
@@ -133,6 +136,27 @@ public class World {
 		
 		return new Shape3D(geometry);
 	}
+	
+	private void addHalfspaces() {
+		Point3d lower = new Point3d();
+		Point3d upper = new Point3d();
+		myVirtualWorldBounds.getLower(lower);
+		myVirtualWorldBounds.getUpper(upper);
+		
+		// Bottom
+		myObjects.add(new HalfSpace(new Vector3f(lower), new Vector3f(0, 1, 0)));
+		
+		// Top
+		myObjects.add(new HalfSpace(new Vector3f(upper), new Vector3f(0, -1, 0)));
+		
+		// Sides
+		myObjects.add(new HalfSpace(new Vector3f(upper), new Vector3f(0, 0, -1)));
+		myObjects.add(new HalfSpace(new Vector3f(upper), new Vector3f(-1, 0, 0)));
+		
+		myObjects.add(new HalfSpace(new Vector3f(lower), new Vector3f(0, 0, 1)));
+		myObjects.add(new HalfSpace(new Vector3f(lower), new Vector3f(1, 0, 0)));
+		
+	}
 
 	/**
 	 * Add some standard lights to the world.
@@ -193,8 +217,9 @@ public class World {
 		
 		// Collision Detection
 		for (int i = 0; i < myObjects.size() - 1; i++) {
-			for (int j = i + 1; j < myObjects.size(); j++)
+			for (int j = i + 1; j < myObjects.size(); j++) {
 				myObjects.get(i).resolveCollisions(myObjects.get(j));
+			}
 		}
 
 		// Add new children to thr world.
@@ -251,4 +276,27 @@ public class World {
 	public void addForce(final Force force) {
 		myForces.add(force);
 	}
+	
+	/**
+	 * Remove a force from the world.
+	 * 
+	 * @param force The force to remove.
+	 */
+	public void removeForce(final Force force) {
+		myForces.remove(force);
+	}
+	
+	/**
+	 * Remove all forces and objects from the world.
+	 */
+	public void resetWorld() {
+		myForces.clear();
+		
+		for (PhysicalObject obj : myObjects) {
+			obj.detach();
+		}
+		myObjects.clear();
+		
+		addHalfspaces();
+	}
 }	
diff --git a/src/tesseract/menuitems/PlanarPolygonMenuItem.java b/src/tesseract/menuitems/PlanarPolygonMenuItem.java
index 6759f19..e85cfbc 100644
--- a/src/tesseract/menuitems/PlanarPolygonMenuItem.java
+++ b/src/tesseract/menuitems/PlanarPolygonMenuItem.java
@@ -76,7 +76,7 @@ public class PlanarPolygonMenuItem extends TesseractMenuItem {
 					setMass(mass);
 	
 				if (event.getSource() == enterButton) {
-					myWorld.addObject(new Ellipsoid(getPosition(), getRadius()));
+					myWorld.addObject(new PlanarPolygon(getPosition(), getRadius()));
 					params.dispose();
 				}
 			}
diff --git a/src/tesseract/objects/HalfSpace.java b/src/tesseract/objects/HalfSpace.java
new file mode 100644
index 0000000..df3f715
--- /dev/null
+++ b/src/tesseract/objects/HalfSpace.java
@@ -0,0 +1,17 @@
+package tesseract.objects;
+
+import javax.vecmath.Vector3f;
+
+public class HalfSpace extends PhysicalObject {
+	public Vector3f normal;
+	// Right-hand side of the plane equation: Ax + By + Cz = D
+	public float intercept;
+
+	public HalfSpace(Vector3f position, Vector3f normal) {
+		super(position, Float.POSITIVE_INFINITY);
+
+		this.normal = new Vector3f(normal);
+		this.normal.normalize();
+		this.intercept = this.normal.dot(position);
+	}
+}
diff --git a/src/tesseract/objects/PhysicalObject.java b/src/tesseract/objects/PhysicalObject.java
index 2634ca2..73e0c91 100644
--- a/src/tesseract/objects/PhysicalObject.java
+++ b/src/tesseract/objects/PhysicalObject.java
@@ -22,9 +22,12 @@ import com.sun.j3d.utils.geometry.Primitive;
  * @author Jesse Morgan
  */
 public class PhysicalObject extends CollidableObject {
+	protected boolean collidable;
+	
 	public PhysicalObject(final Vector3f thePosition, final float mass) {
 		super(mass);
 		this.position.set(thePosition);
+		collidable = true;
 	}
 
 	public List<PhysicalObject> spawnChildren(final float duration) {
@@ -67,7 +70,7 @@ public class PhysicalObject extends CollidableObject {
 	}
 
 	public void resolveCollisions(final PhysicalObject other) {
-		if (this.node != null && other.node != null) {
+		if (collidable && other.collidable) {
 			super.resolveCollisions(other);
 		}
 	}
diff --git a/src/tesseract/objects/emitters/ParticleEmitter.java b/src/tesseract/objects/emitters/ParticleEmitter.java
index 5aa391a..15c94a9 100644
--- a/src/tesseract/objects/emitters/ParticleEmitter.java
+++ b/src/tesseract/objects/emitters/ParticleEmitter.java
@@ -43,6 +43,7 @@ public class ParticleEmitter extends PhysicalObject {
 			final Color3f color) {
 		
 		super(position, Float.POSITIVE_INFINITY);
+		this.collidable = false;
 		
 		myCount = 0;
 		myFrequency = frequency;