text: Checking and updating value of decision parameter based on algorithm
code: if ( d1 < 0 ) { x ++ ; dx = dx + ( 2 * ry * ry ) ; d1 = d1 + dx + ( ry * ry ) ; } else { x ++ ; y -- ; dx = dx + ( 2 * ry * ry ) ; dy = dy - ( 2 * rx * rx ) ; d1 = d1 + dx - dy + ( ry * ry ) ; } }