code: @Pure
  	public DoubleProperty depthProperty() {
  		if (this.depth == null) {
  			this.depth = new ReadOnlyDoubleWrapper(this, MathFXAttributeNames.DEPTH);
  			this.depth.bind(Bindings.subtract(maxZProperty(), minZProperty()));
  		}
  		return this.depth;
  	}
docs: Replies the property that is the depth of the box.
  
  @return the depth property.