linear segment u a t u 0 t u 1 u2212 u 0 and u b u2061 t u u2061 1 2 1 2 u2062 u2202 u u2202 t u2062 1 2 t u2062 1 2 u2062 u2202 u u2202 t u2062 1 2 and on the right shows a set of linear curves are bounded by a lower and upper linear approximation the derivation of a patch is described below if the triangle intersects the w f plane the culling test is disabled for this triangle for a given screen space tile t i we retrieve a linear function u i min k i t m i from the bilinear representation below which we can cull all samples the upper linear bound is derived similarly and gives a second line above which we can cull all samples applying the same technique to v ij t in equation 1 we can derive two bounding lines in vt space for each tile we evaluate the bilinear patches p u min x t and p u max x t at the tile center at a cost of 4 fused multiply add fma operations to find two bounding lines in ut space axis aligned bounds for u are then obtained by a min and a max operation the total cost per tile for bounds in.