text: /**
  * MyVoxelHill
  * @constructor
  */
  class MyVoxelHill extends CGFobject {
      constructor(scene, levels) {
          super(scene);
          
          this.levels = levels;
          this.cube = new MyUnitCubeQuad(scene, 'images/mineSide.png', 'images/mineTop.png', 'images/mineBottom.png');  
                  
          this.initBuffers();
      }
      
      initBuffers() {
          this.vertices = [];
  
  		//Counter-clockwise reference of vertices
  		this.indices = [];
  		this.primitiveType = this.scene.gl.TRIANGLES;
  		this.initGLBuffers();
      }
      
      display() {
          let y = 0;
  
          for(let n = this.levels; n > 0; n--) {         //Movement in the y axis        
              let limit = 2*n - 1;
              let x = -n + 1;
  
              for(let i = 1; i <= limit; i++) {          //Movement in the x axis
                  let z = -n + 1;
  
                  for(let j = 1; j <= limit; j++) {      //Movement in the z axis  
  
                      if(n == this.levels || i == 1 || i == limit || j == 1 || j == limit) {  //optimization
                          this.scene.pushMatrix();
                          this.scene.translate(x, y, z);
                          this.cube.display();
                          this.scene.popMatrix();
                      }                
  
                      z++;
                  }
  
                  x++;
              }
  
              y++;
          }      
      }
  }