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From Point Clouds To Trimmed NURBS

Digitize geometry, create new objects, and model challenging shapes using NURBS, an industry-standard compact representation. Overcome noisy and missing data with advanced techniques like smoothing and hole filling.

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From Point Clouds To Trimmed NURBS

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  1. From Point Clouds To Trimmed NURBS

  2. MOTIVATION Digitizing Geometry • CAD Modeling • Field of Entertainment http://www.qcinspect.com/rev.htm

  3. Reverse Engineering Point clouds Surfaces • Manipulate existing objects • Create new objects from existing objects • Model objects otherwise difficult to model

  4. Common Surface Representations • NURBS • Industry Standard • Compact Representation • Intuitive Shape Control • Triangle Meshes

  5. Point Cloud Data Characteristics • Large data sets • Holes in the Geometry Problems • Noisy • Missing data

  6. Our Approach • Smoothing for noise removal • Hole filling and triangulation • Parameterization • Fitting by blending local fits

  7. Smoothing • Find the local neighborhood of each point • Project each point onto the surface obtained using MLS approximation about that point

  8. Hole Filling • Local Method • Introduce points in the parameterization • Introduce points radially inwards along the boundary of the hole. • Project each point onto its MLS surface • Triangulate

  9. Hole Filling – Curve Example

  10. Hole Filling

  11. Triangulate Hole • Step 1: Eliminate extremely small angles along the border by introducing a new triangle • Triangulating Hole • Step 2: Introduce new point for each point in the border and simultaneously add it to the closest triangle. Repeat Step 1 and Step 2 until you have a boundary with just 3 vertices.

  12. Triangulation Step 2 Unfilled Hole Step 1 Unfilled Hole Filled and Triangulated

  13. Hole Filling

  14. Parameterization • Harmonic maps

  15. Data Fitting Moving Least Squares • Least Squares Fit • Moving Least Squares fit at point (xj , yj)

  16. Fitting • Hierarchial Subdivision of Domain

  17. Blending Local Fits

  18. Blending Local Fits

  19. The Tank Model Engine Wheel

  20. Parts of the Tank Model

  21. Blending Fits- Surface

  22. Engine from the Tank Model

  23. Extending Boundaries(Completing Rectangular Domain)

  24. Completing the Parametric Domain

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