nl_tokens: Checks if a vertex is visible .
pl_tokens: function checkInView ( m , v ) { var vpp = applyRotPerspToVec ( m , v ) ; var winX = vpp [ 0 ] * vpp [ 3 ] ; var winY = vpp [ 1 ] * vpp [ 3 ] ; var winZ = vpp [ 2 ] * vpp [ 3 ] ; var ret = [ 0 , 0 , 0 ] ; if ( winX < - 1 ) ret [ 0 ] = - 1 ; if ( winX > 1 ) <mask> [ 0 ] = 1 ; if ( winY < - 1 ) ret [ 1 ] = - 1 ; if ( winY > 1 ) ret [ 1 ] = 1 ; if ( winZ < - 1 || winZ > 1 ) ret [ 2 ] = 1 ; return ret ; }