289 - Tetrahedron

//
//  Tetrahedron.java
//  Easel
//
//  Created by Philip Rhodes on 8/2/05.
//  Copyright 2005 Philip J Rhodes. All rights reserved.
//


/*
 * This class represents a tetredron. It is placed on the zero plane
 *  with its top vertex on the y axis. On the base, two points are placed
 *  symmetrically on either side of the positive z axis, and the third
 *  point is placed behind, on the negative z axis.
 */
public class Tetrahedron extends Shape{


   public Tetrahedron(float size){

      // This shape needs 4 vertices and 4 triangles.
      super(4, 4);

      this.setScales(size, size, size);

      float d = (float) (1/(2*Math.cos(Math.PI/6)));

      setVertex(0,   0,     (float) Math.sqrt(1-d*d),  0);
      setVertex(1,   0,     0,                        -d);

      setVertex(2,   0.5f,  0, (float) Math.tan(Math.PI/6)/2);
      setVertex(3,   -0.5f, 0, (float) Math.tan(Math.PI/6)/2);

      // CCW Winding Order
      setTriangle(0, 1, 2, 3);
      setTriangle(1, 0, 2, 1);
      setTriangle(2, 0, 1, 3);
      setTriangle(3, 0, 3, 2);

   }

}