CODEWITHSUNDEEP
graphics3dvisualization
shoosh
shoosh

Reputation: 78934

3D laser scanner capturing normals?

The Lab university I work at is in the process of purchasing a laser scanner for scanning 3D objects. All along from the start we've been trying to find a scanner that is able to capture real RAW normals from the actual scanned surface. It seems that most scanners only capture points and then the software interpolates to find the normal of the approximate surface.

Does anybody know if there is actually such a thing as capturing raw normals? Is there a scanner that can do this and not interpolate the normals from the point data?

Upvotes: 4

Views: 1311

Answers (5)

Ofer
Ofer

Reputation: 21

Here is an example article of using structured light to reconstruct normals from gradients. Shape from 2D Edge Gradients

I didn't find the exact article I was looking for, but this seems to be on the same principle. You can reconstruct normals from the angle and width of the stripe after being deformed on the object.

Upvotes: 2

Meekohi
Meekohi

Reputation: 10892

Capturing raw normals is almost always done using photometric stereo. This almost always requires placing some assumptions on the underlying reflectance, but even with somewhat inaccurate normals you can often do well when combining them with another source of data:

Really nice code for combining point clouds (from a laser scan for example) with surface normals: http://www.cs.princeton.edu/gfx/pubs/Nehab_2005_ECP/

Upvotes: 1

Martin Beckett
Martin Beckett

Reputation: 96109

You could with a structured light + camera setup.
The normal would come from the angle betwen the projected line and the position on the image. As the other posters point out - you can't do it from a point laser scanner.

Upvotes: 1

Bob Cross
Bob Cross

Reputation: 22292

If you already know the bidirectional reflectance distribution function of the material that composes your 3D object, it is possible that you could use a gonioreflectometer to compare the measured BRDF at a point. You could then individually optimize a computed normal at that point by comparing a hypothetical BRDF against the actual measured value.

Admittedly, this would be a reasonably computationally-intensive task. However, if you are only going through this process fairly rarely, it might be feasible.

For further information, I would recommend that you speak with either Greg Ward (Larson) of Radiance fame or Peter Shirley at NVIDIA.

Upvotes: 2

starmole
starmole

Reputation: 994

Highly unlikely. Laser scanning is done using ranges. What you want would be combining two entirely different techniques. Normals could be evaluated with higher precision using well controlled lighting etc, but requiring a very different kind of setup. Also consider the sampling problem: What good is a normal with higher resolution than your position data?

Upvotes: 2

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