1. Methods for Fitting CSG Models to Point Clouds and their Comparison
T.Rabbani
May 14, 2019
Section of Photogrammetry and Remote Sensing
Faculty of Aerospace Engineering

2. CSG Fitting – Why and How?
Library of CAD models is useful for industrial scenes
CSG is a compact and flexible representation scheme
Main problem: Calculation of distance of a point from estimated model surface and its partial derivatives
Three methods are compared:
ICS (Iterative Closest Surface-point)
ICT (Iterative Closest Triangle-point)
ICP (Iterative Closest Pointcloud-point)
May 14, 2019

3. Application Domain – Industrial Reconstruction
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4. Traditional vs CSG Fitting
Traditional Approach
Scans
Segmentation
Fitting
Editing
CAD B-rep
Object knowledge
CSG Fitting
CSG Fitting
CAD CSG
Object knowledge
Scans
Segmentation
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5. Traditional Fitting (Example)
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6. CSG Fitting (Example)
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7. Constructive Solid Geometry (CSG)
CSG tree: primitives, constraints, operations
Flanged T-junction
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8. Three distance approximations
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9. Before fitting
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10. Iterative Closest Surface-point (ICS)
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11. Iterative Closest Triangle-point (ICT)
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12. Iterative Closest Point-cloud-point (ICP)
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13. Fitting – Problem Formulation
= shortest distance of a given point
from
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14. Fitting method
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15. Finite difference approximation of partial derivatives
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16. Example 1 – Before Fitting
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17. Example 1 – After ICS
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18. Example 1 – After ICT
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19. Example 1 – After ICP
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20. Example 2 – Before Fitting
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21. Example 2 – After ICS
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22. Example 2 – After ICT
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23. Example 2 – After ICP
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24. Comparison
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26. Future: Combined Fitting
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27. Future plans:
Automatic object recognition using a library of CSG objects
Combined fitting using images and point clouds
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28. Questions:
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