SYNOPSIS:
    VOLPOS_REL vector

DESCRIPTION:
    Move the camera relative to the current volume coordinate system.
    That is, if the camera currently is right in the middle of voxel
    100,200,300 and it is moved vy 10,20,30 it will end up in the
    middle of voxel 110,220,330.

SEE ALSO:
    POS, CPOS, DIR
