Conversion of a hierarchical subdivision surface to nurbs

• US 20030197701A1
• Filed: 04/23/2002
• Published: 10/23/2003
• Est. Priority Date: 04/23/2002
• Status: Active Grant

• Current Assignee: Autodesk, Inc.
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Lounsbery, Michael, Teodosiadis, Steve
• Granted Patent: US 6,859,202 B2
• Time in Patent Office: Days
• US Class Current: 345/420
• CPC Class Codes: G06T 17/30 Polynomial surface description

Abstract

A method of converting a subdivision surface to a NURBS representation. Adjacent faces of a subdivision surface are merged into a quadrilateral region, and vertices of the rectangular regions are used to generate a NURBS surface. The merging of faces reduces the number of vertices needed. Faces should not be merged if they do not comprise a quadrilateral region; if they cross an extraordinary point; if they cross a crease; or a face has already been merged. Imaginary vertices can be generated if not enough vertices are present for a face in the subdivision surface to create a corresponding NURBS patch for that face.

Claims

1. A method of creating a NURBS surface from a subdivision surface, comprising:

merging subdivision faces of a same level into one or more regions; and

converting each region into a NURBS surface.

2. A method of converting a subdivision surface to NURBS, comprising:

merging adjacent faces of the subdivision surface into a quadrilateral region; and

collecting vertices of the quadrilateral region.

3. A method as recited in claim 2, further comprising creating a NURBS surface from the vertices.

4. A method as recited in claim 2, further comprising storing the vertices into a file format readable by a NURBS application.

5. A method as recited in claim 2, wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition.

6. A method as recited in claim 5, wherein the stop condition comprises merging over an extraordinary point.

7. A method as recited in claim 5, wherein the stop condition comprises merging over a crease.

8. A method as recited in claim 5, wherein the stop condition comprises merging a duplicate face.

9. A method as recited in claim 2, further comprising repeating the merging until all faces of the subdivision surface are merged or are unable to be merged.

10. A method as recited in claim 2, wherein the merging and collecting first starts with all level 1 faces, and then is repeated for each subsequent face level.

11. A method as recited in claim 2, wherein the merging selects adjacent faces by using a spiral pattern.

12. A method as recited in claim 2, wherein the collecting vertices further comprises generating imaginary vertices when needed.

13. A method of converting a subdivision surface to NURBS, comprising:

merging adjacent faces into a quadrilateral region, the adjacent faces are selected using a spiral pattern, the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition, the stop condition comprising crossing an extraordinary point, crossing a crease, and crossing a duplicate face;

repeating the merging until all faces are merged or unable to merge;

collecting vertices of the merged regions;

generating imaginary vertices when needed;

after performing the merging and collecting for all level 1 faces, performing the merging, repeating, collecting and generating for each subsequent face level;

storing the vertices into a file format readable by a NURBS application; and

creating a NURBS surface from the vertices.

14. A method, comprising:

merging adjacent selected subdivision faces into parameter regions of a subdivision surface, the faces to merge are selected based on preset merging conditions, and

storing vertices of the parameter regions into a file.

15. A method, comprising:

merging adjacent selected subdivision faces into parameter regions of a subdivision surface, the faces to merge are selected based on preset merging conditions, and

creating a NURBS surface from vertices of the parameter regions.

16. A method comprising:

merging faces of a subdivision surface; and

converting the merged faces to a NURBS representation.

17. A method comprising converting merged faces of a subdivision surface into a NURBS representation.

18. A method of converting a polygonal surface to NURBS, comprising:

merging adjacent faces of the polygonal surface into a quadrilateral region; and

collecting vertices of the quadrilateral region.

19. A method as recited in claim 18, further comprising creating a NURBS surface from the vertices.

20. A method as recited in claim 18, further comprising storing the vertices into a file format readable by a NURBS application.

21. A method as recited in claim 18, wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition.

22. A method as recited in claim 18, wherein the stop condition comprises merging over an extraordinary point.

23. A method as recited in claim 18, wherein the stop condition comprises merging over a crease.

24. A method as recited in claim 18, wherein the stop condition comprises merging a duplicate face.

25. A method as recited in claim 18, further comprising repeating the merging until all faces of the polygonal surface are merged or are unable to be merged.

26. A method as recited in claim 18, wherein the merging and collecting first starts with all level 1 faces, and then is repeated for each subsequent face level.

27. A method as recited in claim 18, wherein the merging selects adjacent faces by using a spiral pattern.

28. A method as recited in claim 18, wherein the collecting vertices further comprises generating imaginary vertices when needed.

34. A computer readable storage as recited in claim 18, further controlling a computer by creating a NURBS surface from the vertices.

36. A computer readable storage as recited in claim 18, further controlling a computer by creating a NURBS surface from the vertices.

29. A method, comprising:

merging adjacent selected polygon faces into parameter regions of a polygonal surface, the faces to merge are selected based on preset merging conditions, and

storing vertices of the parameter regions into a file

30. A method, comprising:

merging adjacent selected polygon faces into parameter regions of a polygonal surface, the faces to merge are selected based on preset merging conditions, and

creating a NURBS surface from vertices of the parameter regions.

31. A method comprising:

merging faces of a polygonal surface; and

converting the merged faces to a NURBS representation.

32. A method comprising converting merged faces of a polygonal surface into a NURBS representation.

33. A computer readable storage controlling a computer by,

merging adjacent faces of a subdivision surface into a quadrilateral region;

and

collecting vertices of the quadrilateral region.

35. A computer readable storage controlling a computer by,

merging adjacent faces of a polygonal surface into a quadrilateral region;

and

collecting vertices of the quadrilateral region.

38. An apparatus as recited in claim 35, wherein the computer creates a NURBS surface from the vertices.

40. An apparatus as recited in claim 35, wherein the computer creates a NURBS surface from the vertices.

37. An apparatus, comprising:

a storage storing a subdivision surface; and

a computer merging adjacent faces of the subdivision surface into a quadrilateral region and collecting vertices of the quadrilateral region.

39. An apparatus, comprising:

a storage storing a polygonal surface; and

a computer merging adjacent faces of the polygonal surface into a quadrilateral region and collecting vertices of the quadrilateral region.