A computer-implemented method for designing a 3D modeled object that represents a part, wherein the method comprises the steps of: ▪ providing a base mesh controlling a subdivision surface, the subdivision surface modeling the 3D modeled object; ▪ providing a polyline consisting of connected edges of the base mesh; ▪ providing definition of a smooth portion of the polyline comprising an extremity of the polyline, wherein the extremity of the polyline is an end point of the polyline, and of a sharp portion of the polyline upstream the smooth portion, upstream being toward the direction on the polyline other than the direction toward the extremity comprised in the smooth portion, wherein the definition of the smooth portion comprises definition of a smooth point on the polyline, the smooth portion being delimited by the smooth point and the extremity of the polyline, wherein the definition of the sharp portion comprises definition of a sharp point on the polyline upstream the smooth point, the sharp portion being delimited by the sharp point and being upstream the sharp point, the smooth point and the sharp point being created by a user to delimit the smooth portion and sharp potion according to a process which allows the creation of a point distinct from a vertex of the base mesh; and ▪ converting faces of the mesh adjacent to the polyline into parametric patches approximating the subdivision surface, in which the patches have a G0 connection across the sharp portion of the polyline, and the patches have a G i connection across the smooth portion of the polyline, where i is an integer higher or equal to 1; wherein the converting step comprises: ▪ converting faces adjacent to edges of the polyline intersecting the smooth portion into first patches, in which said conversion applies a G i connection attribute to said edges; and ▪ converting faces adjacent to edges of the polyline intersecting the sharp portion into second patches, in which said conversion applies a G0 connection attribute to said edges thus resulting in a sharp curve on the assembly of the second patches, said sharp curve corresponding to said edges; then ▪ trimming the second patches downstream the sharp point. further comprising ▪ extrapolating the sharp curve; ▪ projecting the extrapolation of the sharp curve on the first patches; ▪ determining a connection curve by blending the projection of the extrapolation of the sharp curve with the sharp curve; then ▪ filling the two holes formed between the first patches, the second patches, the connection curve, and patches corresponding to faces of the mesh not adjacent to the polyline. ▪ providing a base mesh controlling a subdivision surface, the subdivision surface modeling the 3D modeled object; ▪ providing a polyline consisting of connected edges of the base mesh; ▪ providing definition of a smooth portion of the polyline comprising an extremity of the polyline, wherein the extremity of the polyline is an end point of the polyline, and of a sharp portion of the polyline upstream the smooth portion, upstream being toward the direction on the polyline other than the direction toward the extremity comprised in the smooth portion, wherein the definition of the smooth portion comprises definition of a smooth point on the polyline, the smooth portion being delimited by the smooth point and the extremity of the polyline, wherein the definition of the sharp portion comprises definition of a sharp point on the polyline upstream the smooth point, the sharp portion being delimited by the sharp point and being upstream the sharp point, the smooth point and the sharp point being created by a user to delimit the smooth portion and sharp potion according to a process which allows the creation of a point distinct from a vertex of the base mesh; and ▪ converting faces of the mesh adjacent to the polyline into parametric patches approximating the subdivision surface, in which the patches have a G0 connection across the sharp portion of the polyline, and the patches have a G i connection across the smooth portion of the polyline, where i is an integer higher or equal to 1; ▪ converting faces adjacent to edges of the polyline intersecting the smooth portion into first patches, in which said conversion applies a G i connection attribute to said edges; and ▪ converting faces adjacent to edges of the polyline intersecting the sharp portion into second patches, in which said conversion applies a G0 connection attribute to said edges thus resulting in a sharp curve on the assembly of the second patches, said sharp curve corresponding to said edges; then ▪ trimming the second patches downstream the sharp point. ▪ extrapolating the sharp curve; ▪ projecting the extrapolation of the sharp curve on the first patches; ▪ determining a connection curve by blending the projection of the extrapolation of the sharp curve with the sharp curve; then ▪ filling the two holes formed between the first patches, the second patches, the connection curve, and patches corresponding to faces of the mesh not adjacent to the polyline.