The present invention provides methods for pruning the roots of tree seedlings. In an exemplary design, an apparatus includes first, second, and third signal lines and a switch. A platform for supporting the ATM has a front end, a rear end and opposite first and second side margins. A transmission timer is started upon sending the transmission. The photographer is informed of parameters, which implements a display state adjusted by an observer of a three-dimensional display while observing the three-dimensional image, via the viewer, and the photographer can capture appropriate multi-viewpoint images. The transition between dilated mode and constricted mode can occur under full power.