Inspec Insights

Scan Data Output: Point Cloud or Surfaced Model?

Nov 06, 2014


By Edmond Pietila, Inspection/QA Manager

You have a part, fixture, mold or tool you want scanned.  You send it to an Inspection Laboratory to be scanned.   They ask, what data output do you need; a Point Cloud, or Surfaced Model, or something else?  If you don’t know what to ask for, you probably won’t get the results you need.

To prevent this scenario, Inspec educates clients on the difference between a Point Cloud and a Surfaced Model and how each is commonly used.

POINT CLOUD:

A point cloud is normally created from Laser Scan and is a series of coordinates for each point captured by the scanning process.  Scanned data can be received in several formats:

  1. A text file (extension .txt)
    1. This is a file which can be read in most word processing software (depending on the size of the file) including Notepad, WordPad, Microsoft Word (and Excel, with special preparation within Excel)
    2. The format is a series of X, Y, Z coordinates, separated by a space
    3. Example (this is only 3 points, normally there are thousands to millions of points):

      1729.008952 -73.242603 1256.654082

      1728.714518 -72.219565 1257.394237

      1727.958658 -69.610661 1259.216224

  2. A Comma Separated Variables file (extension .csv)
    1. This file can be read by the same software indicated for .txt but also can be read into Excel, putting each coordinate (X, Y or Z) in a separate cell and a new row for each point.The default (when double-clicked) is Excel.
    2. The format is a series of X, Y, Z coordinates, separated by commas
    3. Example (same 3 points):

      1729.008952,-73.242603,1256.654082

      1728.714518,-72.219565,1257.394237

      1727.958658,-69.610661,1259.216224

  3. A 3D software package (some common extensions are .igs, .stp, .dwg, .3dm)
    1. This file can be read by 3D software packages and at times can be very limited in what software can open it.Several however - .igs, .stp for example – are able to be read by almost all 3D software.
    2. The format is unique to the specific 3D software and generally is not able to be read (or at least easily understood) in a word type of software.
    3. Example of .igs (same 3 points – note coordinate at the bottom):

 

SURFACING:
Surfacing is the process of converting the Point Cloud into a model with surfaces.  As an example, a point cloud of a cup could not hold water, while the point cloud cup, after it has been surfaced, can hold water.  The model has a complete surface whereas the point cloud is just a lot (a real lot!) of points positioned in the shape of a cup.  Surfaced files can be received in several formats:

  1. A 3D software package (some common extensions are .igs, .stp, .stl, .3dm)
    1. This file can be read by 3D software packages and at times can be very limited in what software can open it.Several however - .igs, .stp for example – are able to be read by almost all 3D software.
    2. The format is unique to the specific 3D software and generally is not meant to be read in a word type of software.

Example of same part as:                    .

      Surfaced                                                  Point Cloud

 

  

 

 

 

 

 

Close-up of front sight:                .

  

What Is This Going To Costs?

  1. Point Clouds have most of the cost in the set-up and scanning of the object.At that point the work is essentially done.If a color map is desired, the nominal CAD model is required, which will add slightly to the cost of the processing.
  2. Surfaced Models cost more than Point Clouds. They are normally created from Point Clouds, then processed to convert the groups of points into specific features with the end result of creating a solid model.Most of the cost is in the processing of the data after the scan is completed.The additional cost varies widely and is dependent on the amount of surfacing required, ranging from a simple shell (50% to 100% additional cost) to a completely solid model (5 to 10 times additional cost).Surfaced Model processing must be done by a very competent person.
  3. In an effort to save money, some companies think that they can “do the rest”, if they just get a point cloud.Unfortunately, to often that’s not the case, and eventually the company pays to have a professional do the surfacing.
So Which Should You Use?Point Cloud if:
  1. You want a color map to show the variation of the actual item compared to the ideal (nominal – CAD model is required).In this image, the blue indicates there is less material than there should be.
  2. You want to process the data using your own software or spreadsheet
Surfaced Model if:
  1. You want to use the information for cutting new items (think CNC).Most systems cannot use Point Clouds to determine cutter paths.
  2. You want to more clearly visualize how the item appears (see images above) 

No matter your particular data needs, Point Clouds or Surfaced Model, Inspec has your solution.

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