Updated: February 11, 2021
This article covers 3D scanning with Artec scanners and a special photogrammetry kit, as well as a DIY point cloud created and exported using the Artec Studio software.
For illustration purposes, we use the AICON ScanReference photogrammetry kit (currently known as AICON DPA Entry). It is also possible to use another solution, such as LINEARIS3D or any other photogrammetry package that supports non-coded targets (see the additional information about the structure of the supported OBC/CSV files, below).
A video, illustrating the main processes of using a photogrammetry kit, is available here.
In general, the use of photogrammetry allows us to create a very accurate point cloud, containing the coordinates of the non-coded targets attached to the object's surface. Thereafter, we can use this point cloud to automatically align the data captured during the scanning process of the object, to improve the data registration quality and reduce post-processing.
When to use photogrammetry
Photogrammetry is primarily useful for improving accuracy when scanning over large distances (from one to several meters). Its main features are:
- Little or no post-processing
- No manual alignment
- Reliable registration during the scanning process
- Guaranteed accuracy over large distance (for example, for AICON it is ± (0.05 mm + 0.05 mm/m)
- Artec Studio (version 9.2 or later)
- Artec 3D scanner capable of capturing texture (Leo, Eva, MHT, Spider)
- Photogrammetry kit* (see a sample photo below)
*Photogrammetry kit is not required when scanning using a point cloud created in Artec Studio.
Scanning with the AICON ScanReference photogrammetry kit
- Make sure you have sufficient space to move all the way around the object at a distance of 0.5 – 1 m.
- If the object is tall, make sure that you can safely capture it from above (for example, using a chair, stepladder, etc).
- Ensure that you have enough lighting in the room to capture good quality photos.
The reference cross and non-coded targets
- Place the non-coded targets onto the object’s surface so that at least 6 targets are always visible in the scanner's field of view.
- standard non-coded targets (white dot in black circle) are available in various sizes
- use larger targets for scanning with Artec Leo, Eva, and MHT scanners (we recommend 5 mm inside diameter, 10 mm outside diameter targets)
- smaller targets can be also used for scanning with Artec Spider (for example: 3 mm inside diameter, 5 mm outside diameter)
- we do not recommend using light-reflective targets, since these can cause overexposure and reduce the accuracy of the resulting point cloud.
- Avoid gluing the targets to the object edges or to the highly curved surfaces.
- Place the reference cross and coded targets on an even surface.
- Depending upon the object’s size, place the cross in such a way so that it is visible from all/most points of view.
- When placing a coded target, make sure that non-coded targets, the cross and other coded targets are near it.
- We highly recommend placing some targets at different heights (so not all of them are at the same level surface, if possible).
Take all pictures at a distance of 0,5 – 1,5 meters from the object, using the special DSLR camera included with the photogrammetry kit. The camera flash should be enabled.
- The entire cross should be visible in the first 10-12 photos.
- Every photo should contain as many targets as possible, visible at a relatively good viewing angle. The angle is very important because the pattern on the coded targets should be properly recognizable by the software.
- Hold the camera steadily while taking the photos. You can not use blurred photos in further post-processing.
- Capture the first two photos from the same place, rotating the camera by 90° for the second shot.
- For subsequent photos, keep moving around the object in a circle taking pictures of the scene at each step.
- Important: every target should be visible in at least 10 photos.
- If the reference cross is partially or completely hidden from certain points of view, try to capture as many coded targets as possible in one picture.
- You can finish taking pictures once you have made a full circle around the object and captured all the targets in the scene (coded and non-coded).
- Important: do not move the targets or the reference cross during the photo session or thereafter. If they shift by accident, start the whole process again from the very beginning.
Post-processing of the captured photos
- Run the AICON ScanReference software.
- Create a new project.
- Make sure the reference cross size is entered into the software.
- Insert a memory card with the photos, when the software prompts you to do so.
- The software will load and post process your photos automatically.
- When the data processing is complete, check the results to ensure that the software correctly recognized all of the targets in the photos.
- Export the data using OBC file format.
Dimensions of the cross to enter in ScanReference software:
A higher-res version of this picture appears at the end of the article.
3D scanning with photogrammetry using Artec Eva, MHT, or Spider scanner in Artec Studio
Before proceeding to 3D scanning, please remove the coded targets and the reference cross from the scene. These are no longer necessary.
- Specify the size of the non-coded targets used, in File → Settings → Scan → Photogrammetry settings.
- Switch to the "Scan" menu, then choose "Targets" for the “Features to track” option and load the OBC/CSV file created with the photogrammetry into the Artec Studio.
- Start scanning. Important: at least 5 targets should appear in the scanner's field of view at all times during the scanning process.
The software should now automatically detect the non-coded targets (remaining in the scene) and align your captured data to the photogrammetry point cloud.
- You can stop the scanning process at any time. For example, you can stop the scan, move to another position and resume capturing from there.
- All captured scans should be automatically aligned in a single coordinate system using the known target coordinates from your OBC/CSV file.
- To measure the distance between two individual points on the surface of the object, you can now only scan small surface areas around those specific points (there is no need to continuously scan the whole surface in between).
3D scanning with photogrammetry using Artec Leo scanner
For the Leo scanner, the applicable photogrammetry settings should be set up in the scanner’s UI. The OBC/CSV point cloud should also be uploaded onto the scanner itself.
- In the Leo interface, go to Settings → Scanner → Scanning and turn on the “Targets” option.
- For the “Targets” option, go to “Settings” and specify the applicable target size. We recommend to use 5 mm inside diameter and 10 mm outside diameter targets. Supported target size range for Leo is: 1-10 mm inner diameter, and 2-12 mm outer diameter.
- Inside the “Targets” settings, go to “Target file on Leo” and upload your OBC/CSV point cloud onto the scanner. You can upload the file using either an SD card or via the internet (note: only the OBC file format can be uploaded using the SD card).
- Make sure that the uploaded point cloud appears in the list of files in the applicable menu, select it, and click the “Done” button.
- Go back into the “Targets” menu, and select the “Default file” options. Select the point cloud file you’ve uploaded from the list of available files, and click the “Done” button. Make sure that the name of your chosen file appears at the “Default file” line in the “Targets” menu.
- Go back into the main “Projects” menu and start a new project. Once you have the point cloud file properly uploaded and selected, its name should appear at the bottom-right corner of the preview screen.
- Proceed with the scanning process. The scanner should now automatically detect the non-coded targets (illuminated with red color) and align your captured data to the photogrammetry point cloud.
Scanning with the DIY point cloud created and exported using the Artec Studio software
Besides using the photogrammetry kit, you can also create and export a point cloud with the non-coded target coordinates using just the Artec scanner and Artec Studio. This scanning method might be useful for certain scanning applications, which might benefit from improved data registration, no need for manual alignment, little or no post-processing, quick partial scanning for measuring purposes. However, while a special photogrammetry kit is capable of delivering high levels of accuracy, especially over large distances, without it, you will have to depend entirely upon the accuracy of the given scanner and the data registration quality in Artec Studio. Thus, you might not be able to achieve any higher levels of accuracy with the use of the DIY point cloud. To make am OBC/CSV point cloud in Artec Studio, you need to do the following:
- Make a scanning scene, just like you would do with the photogrammetry kit, but only apply the non-coded targets to the surface of the object and its surroundings (if necessary).
- Switch to the "Scan" menu, then choose "Targets" for the “Features to track” option but do not upload an OBC/CSV file.
- Scan the scene in the usual fashion, make sure to have good data coverage.
- Perform Global registration of your scanned data, using Geometry + texture.
- Select the scanned data and go to File → Export → Scans option. In the drop-down menu, choose the OBC file format.
- Proceed with scanning using the exported OBC file as previously described.
Please note, that the scanned scene should have plenty of texture and geometry features for proper registration since this will primarily affect the accuracy of the resulting OBC point cloud.
The option of exporting an OBC file is not available for the Leo scanner, at this time. Therefore, you can only make a DIY OBC point cloud using Artec Spider, Eva, or MHT scanner and Artec Studio.
Post processing in Artec Studio
- If you used the OBC file for scanning, do not perform Fine or Global registration in Artec Studio (your scans are already properly registered in Workspace using the targets coordinates).
- Run the fusion algorithm to combine your raw scans into a 3D model.
- For Smooth or Sharp fusion, you can use the “Remove targets” option. In this case, Artec Studio will remove the small geometry of the non-coded targets from the object's surface when building the 3D model.
- You can also select the same “Remove targets” option for the texture application algorithm, to eliminate your non-coded targets from the object’s texture. This feature is available in Artec Studio 10 and later versions.
- Export your 3D model to the applicable format using the File → Export mesh option.
The structure of OBC/CSV files
We only use the first four columns in the file, which should contain the following information:
1: Target ID (we use values greater than 1 000 for non-coded targets; values below 1 000 are reserved for coded targets and filtered out)
2,3,4: XYZ Coordinates of the non-coded target
The column separator can only be either a space or a semicolon, while the decimal separator - a comma or a period. Below is an example of a valid OBC/CSV file values for a single non-coded target:
1001 12,03 1235,7 292,44
1001 12.03 1235.7 292.44
Q: Can I use any other software besides ScanReference for photogrammetry?
A: Yes, you can use any hardware and software which is capable of generating OBC/CSV point clouds, using non-coded target coordinates, with the necessary file structure.
Q: My photogrammetry software does not support OBC/CSV formats, what can I do?
A: OBC and CSV files are, essentially, text files with a certain internal structure. Technically, you can use any text file with the applicable structure, and save it as an OBC/CSV file. If the file structure is not suitable, you can also use text editing tools capable of data table conversion (such as Excel) to arrange your data using the required structure.
Q: Can I use photogrammetry with 3D-sensors, such as ASUS Xtion Pro Live and Microsoft Kinect?
A: This option was available with some of the earlier Artec Studio versions, but it is no longer supported.
In case you experience any issues with your Artec 3D scanner or require technical assistance with your device or Artec Studio, in the first instance please contact your local Artec dealer/distributor directly. You can also contact the Artec Support Team by clicking on "Submit a request" button on the bottom right part of the screen or by emailing email@example.com