Mario Van Peebles may be too handsome for his own good. His eyes sparkle amid high cheekboned, delicate features that showcase his multicultural lineage. Looking at what could almost be a parody of a hunk, one could easily presume that this actor MUST be vain and shallow--though nothing in his interviews confirms this impression. Perhaps it was inevitable that he should decide to redirect some of his energies behind the camera. In any event, the young hyphenate heeded the advice of his illustrious father, the breakthrough black writer-director-producer Melvin Van Peebles, to first learn the