Three-dimensional cad/cam system

A three-dimensional CAD/CAM method including:

• a primitive generation step of using a differential polyhedron model which is a set of differential polyhedrons including coordinate values of triangle vertices, normal vectors of the triangle vertices, and curved line elements including start/end points consisting of the triangle vertices and tangent vectors at the start/end points to form a curved surface by connecting sides of the differential polyhedron and form a closed surface by connecting curved surfaces with a curved surface boundary line, thereby generating a primitive which is a set of points belonging to the inside of the closed surface;
• a storage step of storing CSG data which represents a solid model in CSG representation by a tree structure of set operations of the primitives;
• a dexel generation step of determining an intersection point between the solid model and a straight line from the intersection point between the closed surface of the primitive and the straight line by a set operation based on the CSG data, thereby generating a dexel which is a line segment group included in the solid model;
• and
• an NC data generation step of generating NC data for positioning a tool on the basis of the dexel.

A three-dimensional CAD/CAM program that causes a computer to execute:

• a primitive generation step of using a differential polyhedron model which is a set of differential polyhedrons including coordinate values of triangle vertices, normal vectors of the triangle vertices, and curved line elements including start/end points consisting of the triangle vertices and tangent vectors at the start/end points to form a curved surface by connecting sides of the differential polyhedron and form a closed surface by connecting curved surfaces with a curved surface boundary line, thereby generating a primitive which is a set of points belonging to the inside of the closed surface;
• a storage step of storing CSG data which represents a solid model in CSG representation by a tree structure of set operations of the primitives;
• a dexel generation step of determining an intersection point between the solid model and a straight line from the intersection point between the closed surface of the primitive and the straight line by a set operation based on the CSG data, thereby generating a dexel which is a line segment group included in the solid model;
• and
• an NC data generation step of generating NC data for positioning a tool on the basis of the dexel.