Surface analysis export

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Nicolas_3SReshaper
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Re: Surface analysis export

Post by Nicolas_3SReshaper » Fri Apr 06, 2018 10:14 am

lastools wrote:
Wed Apr 04, 2018 4:06 pm
Hello from @rapidlasso,

I'm curious how this "deviation value" is stored to LAS/LAZ. Does it use the ability to export additional per point attributes as "extra bytes"? I'd be interested to see a lasinfo report of such an 3DReshaper 2017MR1 export.
gilles_3Dreshaper wrote:
Mon Feb 26, 2018 1:13 pm
the latest version of 3DReshaper 2017MR1 can export to LAZ (including deviation value)
Regards,

Martin
Hello Martin,
Actually we don't use extra bytes, but we simply rescale the intensity value from mix-max to 0-65535 and store it in the intensity field.
Can you tell me more about "extra-bytes" and how to use it ?

a report from lasinfo looks like this

Code: Select all

reporting all LAS header entries:
  file signature:             'LASF'
  file source ID:             0
  global_encoding:            0
  project ID GUID data 1-4:   00000000-0000-0000-0000-000000000000
  version major.minor:        1.2
  system identifier:          'OTHER'
  generating software:        'LASzip DLL 3.1 r0 (170823)'
  file creation day/year:     94/118
  header size:                227
  offset to point data:       227
  number var. length records: 0
  point data format:          2
  point data record length:   26
  number of point records:    1534441
  number of points by return: 0 0 0 0 0
  scale factor x y z:         0.000000006986644 0.000000004621128 0.000000000057163
  offset x y z:               22.233017700524346 -6.552022093381471 0.024382942594183
  min x y z:                  8.259729507834008 -15.7942782991655 -0.089942316291099
  max x y z:                  36.206305893214683 2.690234112402559 0.138708201479465
LASzip compression (version 3.1r0 c2 50000): POINT10 2 RGB12 2
reporting minimum and maximum for all LAS point record entries ...
  X          -2000000000 2000000000
  Y          -2000000000 2000000000
  Z          -2000000000 2000000000
  intensity           0      65535
  return_number       1          1
  number_of_returns   1          1
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      0          0
  scan_angle_rank     0          0
  user_data           0          0
  point_source_ID     0          0
  Color R 0 65535
        G 1542 65535
        B 0 65535
number of first returns:        1534441
number of intermediate returns: 0
number of last returns:         1534441
number of single returns:       1534441
WARNING: for return 1 real number of points by return is 1534441 but header entry was not set.
overview over number of returns of given pulse: 1534441 0 0 0 0 0 0
histogram of classification of points:
         1534441  never classified (0)
Nicolas Mocellin
3DReshaper Product Manager
www.3dreshaper.com

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RobM
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Re: Surface analysis export

Post by RobM » Fri Apr 06, 2018 10:43 am

I've tested 3DReshaper a while ago and really liked its behaviour and handling. Especially the filtering tools are great!

Whats been missing for me with pretty much all of the available software is to be able to get and create rasterdata on the surfaces.
Pointsense is able to do that, but is not able to make the heatmap anymore (sadly). I think this has stopped with AutoCAD 2015.
It used to look like this:

Image

If 3DReshaper would add this feature this would be a major buying point for me. A lot of clients ask for this kind of report, as they can work with the given values really well.

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Re: Surface analysis export

Post by gilles_3Dreshaper » Fri Apr 06, 2018 2:31 pm

Hi Robin,
From the rendering point of view, sounds like 3DReshaper offers something very close to what you are looking for!
See image below
Facade.PNG
This is called a "grid" in 3DReshaper.
You can activate a grid by hitting the icon on the bottom right of 3DR (activated in the image below - in orange!).
There are several options to grids:
  • Direction of the grid: in X, Y or Z or AUTO (closest to the current view)
  • Steps of the grid
  • Display of the text
Grid.PNG
It is also possible to create rasterdata on a mesh.
This function is called "Grid Projection" in the cloud menu.
In uses the Z direction to project points on a mesh (planar mesh I guess here). This means you will have to create a UCS with Z pointing perpendicularly to the facade.
The output is a point cloud which you can compare to/inspect against the facade.
In the compare/inspect dialog, you can ask for a csv report with all deviations.

Hope this helps!
Do not hesitate to ask more!
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Gilles
3DReshaper Manager
http://www.3dreshaper.com

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gilles_3Dreshaper
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Re: Surface analysis export

Post by gilles_3Dreshaper » Fri Apr 06, 2018 2:42 pm

Hi,
Here is a small zip file containing a LAS and a LAZ file exported from 3DReshaper.
LAS+LAZ.zip
Let me know what your findings are about the lasinfo report.

To export a LAS (or LAZ) file in 3DReshaper, just select the point cloud, go to File / Export / Export Selected Cloud(s) and choose the right extension!
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RobM
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Re: Surface analysis export

Post by RobM » Fri Apr 06, 2018 5:20 pm

Hi Gilles,

thank you for your input. That looks really close to what I mentioned.
Unfortunatelly I can't test it myself, as I don't have 3DReshaper (only had a trial about a year ago). But this info might help others!
Also I might get another trial in the future if I have some money to spend on new software ;-)

//edit

is it possible to write the deviation values onto the grid like shown in my example? you can't really tell by the picture i postet, but all the little red marks are text

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Re: Surface analysis export

Post by lastools » Mon Jul 02, 2018 12:04 pm

Hello from @LAStools,
gilles_3Dreshaper wrote:
Fri Apr 06, 2018 2:42 pm
Here is a small zip file containing a LAS and a LAZ file exported from 3DReshaper.
LAS+LAZ.zip
Let me know what your findings are about the lasinfo report.
To export a LAS (or LAZ) file in 3DReshaper, just select the point cloud, go to File / Export / Export Selected Cloud(s) and choose the right extension!
I had a look at the lasinfo report and it looks good except the scale factors and the offset values. This is not the way the LAS / LAZ format was intended to be used. The value in the scale factors specified with what resolution the coordinates are stored and it should match the expected accuracy of the point coordinates. For airborne scans we tend to use scale factors 0.01 0.01 0.01 (aka cm resolution). For mobile scans we tend to use scale factors 0.001 0.001 0.001 (aka mm resolution). For terrestrial scans we tend to use scale factors 0.00025 0.00025 0.00025 (aka quarter-mm resolution).

Your LAS/LAZ files store each point with approximately 9 decimal digits (the digits to the right of the decimal point) because it uses scale factors of 0.000000000150398 0.000000000169045 0.00000000020536. That corresponds to nanometer resolution, which is clearly excessive unless you are scanning with an electron-microscope ... (-:

Also your offsets are really not nice to look at. We usually pick some "rounded" coordinate that is near the point coordinates. The offset is not really needed for local coordinate systems where numbers are close to zero. They are really needed only for projected coordinates (e.g. UTM), geocentric (ECEF), or geometric (long/lat) coordinates where the bounding box enclosing the points is far from zero.

Below I show how to rescale / reoffset the LAZ file you have provided using free and open source las2las of LAStools. Also note the reduction in file size of down to about a third. The nanometer coordinates are not actual information but just whatever "white noise" happened to be in the registers after the floating-point calculations. And "white noise" is more or less incompressible.

Code: Select all

E:\LAStools\bin>las2las -i "Cloud&Inspection.laz" ^
                         -rescale 0.00025 0.00025 0.00025 ^
                         -auto_reoffset ^
                         -odix _qmm -olaz
BEFORE (size 48,862 bytes)

Code: Select all

E:\LAStools\bin>lasinfo -i "Cloud&Inspection.laz"
lasinfo (180620) report for 'Cloud&Inspection.laz'
reporting all LAS header entries:
  file signature:             'LASF'
  file source ID:             0
  global_encoding:            0
  project ID GUID data 1-4:   00000000-0000-0000-0000-000000000000
  version major.minor:        1.2
  system identifier:          'OTHER'
  generating software:        'LASzip DLL 3.1 r0 (170823)'
  file creation day/year:     95/118
  header size:                227
  offset to point data:       227
  number var. length records: 0
  point data format:          2
  point data record length:   26
  number of point records:    4348
  number of points by return: 0 0 0 0 0
  scale factor x y z:         0.000000000150398 0.000000000169045 0.00000000020536
  offset x y z:               -5.061584502268218 4.296448214330293 0.172332938826083
  min x y z:                  -5.362380981254958 3.958358986653901 -0.238388005578519
  max x y z:                  -4.760788023281478 4.634537442006685 0.583053883230685
LASzip compression (version 3.1r0 c2 50000): POINT10 2 RGB12 2
reporting minimum and maximum for all LAS point record entries ...
  X          -2000000000 2000000000
  Y          -2000000000 2000000000
  Z          -2000000000 2000000000
  intensity           0      65535
  return_number       1          1
  number_of_returns   1          1
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      0          0
  scan_angle_rank     0          0
  user_data           0          0
  point_source_ID     0          0
  Color R 29555 30840
        G 22873 51914
        B 5397 39064
number of first returns:        4348
number of intermediate returns: 0
number of last returns:         4348
number of single returns:       4348
WARNING: for return 1 real number of points by return is 4348 but header entry was not set.
overview over number of returns of given pulse: 4348 0 0 0 0 0 0
histogram of classification of points:
            4348  never classified (0)
AFTER (size 15,951)

Code: Select all

E:\LAStools\bin>lasinfo -i "Cloud&Inspection_qmm.laz"
lasinfo (180620) report for 'Cloud&Inspection_qmm.laz'
reporting all LAS header entries:
  file signature:             'LASF'
  file source ID:             0
  global_encoding:            0
  project ID GUID data 1-4:   00000000-0000-0000-0000-000000000000
  version major.minor:        1.2
  system identifier:          'LAStools (c) by rapidlasso GmbH'
  generating software:        'las2las (version 180620)'
  file creation day/year:     95/118
  header size:                227
  offset to point data:       227
  number var. length records: 0
  point data format:          2
  point data record length:   26
  number of point records:    4348
  number of points by return: 4348 0 0 0 0
  scale factor x y z:         0.00025 0.00025 0.00025
  offset x y z:               0 0 0
  min x y z:                  -5.36250 3.95825 -0.23850
  max x y z:                  -4.76075 4.63450 0.58300
LASzip compression (version 3.2r4 c2 50000): POINT10 2 RGB12 2
reporting minimum and maximum for all LAS point record entries ...
  X              -21450     -19043
  Y               15833      18538
  Z                -954       2332
  intensity           0      65535
  return_number       1          1
  number_of_returns   1          1
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      0          0
  scan_angle_rank     0          0
  user_data           0          0
  point_source_ID     0          0
  Color R 29555 30840
        G 22873 51914
        B 5397 39064
number of first returns:        4348
number of intermediate returns: 0
number of last returns:         4348
number of single returns:       4348
overview over number of returns of given pulse: 4348 0 0 0 0 0 0
histogram of classification of points:
            4348  never classified (0)

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