text: Checking and updating parameter value based on algorithm
code: if ( d2 > 0 ) { y -- ; dy = dy - ( 2 * rx * rx ) ; d2 = d2 + ( rx * rx ) - dy ; } else { y -- ; x ++ ; dx = dx + ( 2 * ry * ry ) ; dy = dy - ( 2 * rx * rx ) ; d2 = d2 + dx - dy + ( rx * rx ) ; } } }