IP Library › Granted Patent US 6,859,202
Granted Patent B2
US 6,859,202 · App. 10/127,702 · Granted Feb 22, 2005

Conversion of a hierarchical subdivision surface to nurbs

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Quick Facts
Patent No.
US 6,859,202
App. No.
10/127,702
Granted
Feb 22, 2005
Kind
B2
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 (45)

1. 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, and

wherein the stop condition comprises merging over an extraordinary point.

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, and

wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition, and

wherein the stop condition comprises merging over a crease.

3. 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, and

wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition, and

wherein the stop condition comprises merging a duplicate face.

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

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

collecting vertices of the quadrilateral region, and

wherein the merging selects adjacent faces by using a spiral pattern.

5. 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.

6. 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,

wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition, and

wherein the stop condition comprises merging over an extraordinary point.

7. 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,

wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition, and

wherein the stop condition comprises merging over a crease.

8. 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,

wherein the merging does not merge adjacent faces into a quadrilateral region when the merging would be subject to a stop condition, and

wherein the stop condition comprises merging a duplicate face.

9. A method 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, and

wherein the merging selects adjacent faces by using a spiral pattern.