Cad system and cad program

• US 20060129361A1
• Filed: 10/06/2003
• Published: 06/15/2006
• Est. Priority Date: 10/04/2002
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries, Ltd., PTO (Safe Fleet Holdings LLC)
• Original Assignee: Mitsubishi Heavy Industries, Ltd., PTO (Safe Fleet Holdings LLC)
• Inventors: Yoshida, Yasuhiko, Nakahama, Takeshi, Miura, Masami, Kawano, Takayuki, Sasaki, Yuichi
• Granted Patent: US 7,917,342 B2
• Time in Patent Office: Days
• US Class Current: 703/2
• CPC Class Codes: G06T 17/20 Finite element generation, e.g. wire-frame surface description, tesselation
• CPC Class Codes: G06T 17/30 Polynomial surface description

Abstract

There is provided a computer aided design system and a computer aided design program which can greatly increase the utility value of a computer aided design model, and can improve the efficiency of design and production processes, by adopting a curved surface theory which ensures the continuity of a free-form line/free-form surface. A computer executes: a point sequence information extraction process for extracting a plurality of point sequences on a curved surface; a dividing process for generating a curved surface from the point sequences using another computer graphics program, and dividing the curved surface into a predetermined number of meshes; a first fundamental form computing process for computing coefficients of the first fundamental form defined by a tangent vector which forms a tangent plane of the mesh; a second fundamental form computing process for computing coefficients of the second fundamental form defined by the tangent vector and a normal vector of the mesh; and a storage process for storing the point sequence information, the coefficients of the first fundamental form and the coefficients of the second fundamental form.

Claims

1. A computer aided design system comprising:

a point sequence information extraction device which extracts a plurality of point sequences on a curved surface;

a dividing device which generates a curved surface from said point sequences using another computer aided design system, and divides said curved surface into a predetermined number of meshes;

a first fundamental form computing device for computing coefficients of the first fundamental form defined by a tangent vector which forms a tangent plane of said mesh;

a second fundamental form computing device for computing coefficients of the second fundamental form defined by said tangent vector and a normal vector of said mesh; and

a memory device which stores said point sequence information, said coefficients of the first fundamental form and said coefficients of the second fundamental form.

2. A computer aided design system according to claim 1 further comprising:

a principal curvature computing device which computes a principal curvature of said mesh based on said coefficients of the first fundamental form and coefficients of the second fundamental form;

a line of curvature computing device which computes a line of curvature showing a principal direction of said mesh based on said principal curvature;

a feature point/feature line analyzing device which extracts a point or a line which become a reference point or a reference line of transformation defined by changing patterns of one or more feature quantities among five feature quantities showing features of said curved surface comprising a Gaussian curvature and a mean curvature computed based on said principal curvature, said principal direction, said line of curvature, and said coefficients of the first fundamental form and coefficients of the second fundamental form; and

a girth length computing device which computes a girth length based on a curvature computed from said coefficients of the first fundamental form and coefficients of the second fundamental form.

3. A computer aided design system according to claim 2 further comprising:

a reproducing device which transforms said line of curvature for said girth length in said line of curvature direction, with said feature point or feature line as a transformation reference, and reproduces said mesh or said curved surface.

4. A computer aided design system according to claim 3 further comprising:

a converting device which extracts a plurality of point sequences on a curved surface from said reproduced mesh or curved surface, and converts said point sequences according to a graphical representation algorithm in another computer aided design system.

5. A computer aided design program for executing on a computer:

a point sequence information extraction process for extracting a plurality of point sequences on a curved surface;

a dividing process for generating a curved surface from said point sequences using another computer aided design system, and dividing said curved surface into a predetermined number of meshes;

a first fundamental form computing process for computing coefficients of the first fundamental form defined by a tangent vector which forms a tangent plane of said mesh;

a second fundamental form computing process for computing coefficients of the second fundamental form defined by said tangent vector and a normal vector of said mesh; and

a storage process for storing said point sequence information, said coefficients of the first fundamental form and said coefficients of the second fundamental form.

6. A computer aided design program according to claim 5 for further executing on a computer:

a principal curvature computing process for computing a principal curvature of said mesh based on said coefficients of the first fundamental form and coefficients of the second fundamental form;

a line of curvature computing process for computing a line of curvature showing a principal direction of said mesh based on said principal curvature;

a feature point/feature line analyzing process for extracting a point or a line which become a reference point or a reference line of transformation defined by changing patterns of one or more feature quantities among five feature quantities showing features of said curved surface comprising a Gaussian curvature and a mean curvature computed based on said principal curvature, said principal direction, said line of curvature, and said coefficients of the first fundamental form and coefficients of the second fundamental form; and

a girth length computing process for computing a girth length based on a curvature computed from said coefficients of the first fundamental form and coefficients of the second fundamental form.

7. A computer aided design program according to claim 6 for further executing on a computer,

a reproducing process for transforming said line of curvature for said girth length in said line of curvature direction, with said feature point or feature line as a transformation reference, and reproducing said mesh or said curved surface.

8. A computer aided design program according to claim 7 for further executing on a computer:

a converting process for extracting a plurality of point sequences on a curved surface from said reproduced mesh or curved surface, and converting said point sequences according to a graphical representation algorithm in another computer aided design system.

9. A computer graphics system comprising:

a point sequence information extraction device which extracts a plurality of point sequences on a curved surface;

a dividing device which generates a curved surface from said point sequences using another computer graphics system, and divides said curved surface into a predetermined number of meshes;

a first fundamental form computing device for computing coefficients of the first fundamental form defined by a tangent vector which forms a tangent plane of said mesh;

a second fundamental form computing device for computing coefficients of the second fundamental form defined by said tangent vector and a normal vector of said mesh; and

a memory device which stores said point sequence information, said coefficients of the first fundamental form and said coefficients of the second fundamental form.

10. A computer graphics program for executing on a computer:

a point sequence information extraction process for extracting a plurality of point sequences on a curved surface;

a dividing process for generating a curved surface from said point sequences using another computer graphics system, and dividing said curved surface into a predetermined number of meshes;

a first fundamental form computing process for computing coefficients of the first fundamental form defined by a tangent vector which forms a tangent plane of said mesh;

a second fundamental form computing process for computing coefficients of the second fundamental form defined by said tangent vector and a normal vector of said mesh; and

a storage process for storing said point sequence information, said coefficients of the first fundamental form and said coefficients of the second fundamental form.