Some people are mistakenly trying to apply image processing techniques to point cloud processing, e.g., edge detection in point cloud. Edges by image processing are boundary points of 2-D regions. Point cloud points are boundary points of 3-D volumes..

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Dr.-Ing. Sung Joon Ahn
CurvSurf, Inc.
Some Thoughts on
2-D/3-D Information Processing

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Information 2-D Camera 3-D Camera 3-D CT-Scanner
Primary Pixel Surfel Voxel
Secondary Edgel Surface Surfel
Tertiary 2-D Curve 3-D Curve Surface
Quaternary 2-D Point 3-D Point 3-D Curve
Quinary -- -- 3-D Point
2-D/3-D Information Unit

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Description 2-D Camera 3-D CT-Scanner
Sensor raw data Pixel Voxel
Boundary point of regions Edgel Surfel
Mathematical
representation
2-D Curve Surface
Intersection 2-D Point 3-D Curve
Corner -- 3-D Point
2-D/3-D Information Description
* With 3-D Camera:
Sensor raw data ( = point cloud, surfels ) = Boundary points of 3-D volumes.

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• Pixels are the sensor raw data.
• Edgels are boundary points of regions
and are unstable information.
• Edgels do not much provide information
on regions.
• 2-D curves fitted to edgels represent
mathematically the boundary of regions.
They are relatively stable information
because of average-effect.
• Position, rotation, size, corner, etc. can
be deduced from the 2-D curves fitted.
2-D Information Processing

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• Point cloud (surfels) is the sensor raw data.
• Surfels are boundary points of volumes
and are unstable information.
• Surfels do not much provide information
on volumes.
• Surfaces fitted to surfels represent
mathematically the boundary of volumes.
They are relatively stable information
because of average-effect.
• Position, rotation, size, edge, corner, etc.
can be deduced from the surfaces fitted.
3-D Information Processing (1)

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• Some people are trying to extract more
unstable edgels from unstable point cloud,
ignoring the richness of point cloud.
• Much better is to fit stable surfaces to
unstable point cloud and deduce
more stable information of position,
rotation, size, etc. from the surfaces fitted.
3-D Information Processing (2)
+ + =

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• Further discussions are welcomed
• https://plus.google.com/+CurvSurf
Closing
Thank you!