Patent ID: 11934745
Assignee: DASSAULT SYSTEMES
Field: Computer technology (Electrical engineering)
Classification: CPC G | IPC G

Claim 8:
9. A computer comprising:
a processor coupled to a memory and a display, the memory having recorded thereon a computer program comprising instructions for designing, with a computer-aided design system, a three-dimensional modeled object representing a mechanical part that when executed by the processor causes the processor to be configured to:
obtain a boundary representation representing the mechanical pan, the boundary representation having faces and edges, the boundary representation being displayed,
graphically select, by graphical user interaction with the displayed boundary representation, a first set of faces on the displayed boundary representation;
obtain a feature type, the feature type being either a depression feature type or a protrusion feature type, and
automatically by the computer-aided design system, recognize a second set of faces within the first set of faces, the second set of faces representing a feature of the provided feature type,
wherein the second set of faces forms a connection between one or more elementary subsets, and wherein, a smooth skin being a face or a connected set of faces containing only smooth internal edges:
if the obtained feature type is the depression feature type, an elementary subset in the connection is a connected set of one or more faces bounded by convex edges or round faces only and containing no convex internal edge and no round face in that the one or more faces do not comprise any round face and any edge shared by two faces of the one or more face is not a convex edge, the elementary subset being either not a smooth skin or a smooth skin satisfying a concavity criterion, and
if the obtained feature type is the protrusion feature type, an elementary subset in the connection is a connected set of one or more faces bounded by concave edges or fillet faces only and containing no concave internal edge and no fillet face in that the one or more faces do not comprise any fillet face and any edge shared by two faces of the one or more face is not a concave edge, the elementary subset being either not a smooth skin or a smooth skin satisfying a convexity criterion, wherein the second set of faces comprises all elementary subsets of the first set,

wherein each elementary subset is connected to at least one other elementary subset, two elementary subsets being connected if they share either only edges of a predetermined edge type or only faces of a predetermined face type, where:
if the obtained feature type is the depression feature type, the predetermined edge type is the convex edge type and the predetermined face type is the round face type, and
if the obtained feature type is the protrusion feature type, the predetermined edge type is the concave edge type and the predetermined face type is the fillet face type,

wherein:
a smooth skin bounded by convex edges or round faces only and containing no convex internal edge and no round face satisfies the concavity criterion when the smooth skin cannot be arbitrarily offset in the direction of its normal vector while remaining smooth, and
a smooth skin bounded by concave edges or fillet faces only and containing no concave internal edge and no fillet face satisfies the convexity criterion when the smooth skin cannot be arbitrarily offset in the opposite direction of its normal vector while remaining smooth,

wherein the recognizing further includes:
determining one or more candidate elementary subsets, where:
if the obtained feature type is the depression feature type, a candidate elementary subset is a connected set of one or more faces bounded by convex edges or round faces only and containing no convex internal edge and no round face, and
if the obtained feature type is the protrusion feature type, a candidate elementary subset is a connected set of one or more faces bounded by concave edges or fillet faces only and containing no concave internal edge and no fillet face,

wherein the determining of the one or more candidate elementary subsets partitioning the first set of faces into faces which each belong to exactly one candidate elementary subset and faces which belong to no candidate elementary subset; and
identify the one or more elementary subsets among the determined candidate elementary subsets.