VisibleOnScreen

Function:

 * boolean visibleOnScreen(x, y, z)

Parameters:

 * x }
 * y } position of tile that we want to check if is visible on player's screen.
 * z }

Return value:

 * This function return an boolean indicating if tile with given position (x,y,z) is visible or not on the screen. Returns true if visible, false if not.

Description:

 * This function return an boolean indicating if tile with given position (x,y,z) is visible or not on the screen.