Make the currently active rgl object lighter. Adds a light source. Up to eight light sources can be added. Alternatively, any rgl light source can be added (see light3d).
Examples
x3p <- x3p_read(system.file("sample-land.x3p", package="x3ptools"))
if (FALSE) {
x3p_image(x3p) # run when rgl can open window on the device
x3p_lighter() # add a light source
}