doubled the size of the control point's radius so that it's easier to be picked up
changed the height value of the viewing centre to zero to get a better viewing angle
added the current folder as an alternative path to be searched while loading the resource
adjust the camera to let the terrain be at the center of the screen.
made the control points adjustable using hotkey 'F', and changed the hotkey for toggling the wireframe mode from 'P' to 'Z'
let it not regenerate terrain mesh if dragging without any control point being selected
fixed the overflowing problem of ctrl_point_colors
changed initial camera viewing angle