In this approach, the camera is not moving but it is fixed and the object is rotating on a turntable with visual markers.
IN THIS ARTICLE
Preparation
1. Download the PIX4D visual markers from here.
2. Print the PIX4D visual markers on non-glossy paper. The diameter of the circle enclosing the markers should be around 30 cm.
3. Wrap a turntable with the printed paper.
4. Place a roll of white soft cardboard behind the turntable to hide the background.
5. Mount the camera on a tripod to ensure that it will be steady during the acquisition.
- It is recommended to use a lens with fixed focal length to minimize the parameters that need to be optimized during processing.
- The deeper depth of field can be achieved by selecting aperture around f25.
- It is recommended to illuminate the scene with a source of diffused light to maximize the texture of the object and to reduce the reflections.
Image acquisition
1. Orient the turntable so that the small arrow in the center of the turntable points away from the camera, as in the image below.
2. Place the object on the turntable.
3. Capture the first image.
4. Rotate the turntable by approximately 15 degrees and take a picture. The next marker of the exterior ring should be in front of the camera.
5. Repeat step 4 until one full rotation of the object is completed.
6. Turn the object and place it on the turntable again.
7. Repeat steps 1 to 6 to capture a second dataset from another point of view to fully reconstruct the object. Capture as many datasets as needed to capture the object completely.
Image processing
- Using the PIX4Dtagger to generate the .p4d project file
- Using PiX4Dmapper to process the subprojects
- (optional) Using PIX4Dmapper to merge the subprojects
Using the PIX4Dtagger to generate the .p4d project file
1. Open the PIX4Dtagger. PIX4Dtagger has been installed with PIX4Dmapper from version 2.2 up to 4.5.6. The PIX4Dmapper 4.5.6 installation file is available to download here. The executable is located in the same folder as your PIX4Dmapper executable (PIX4Dmapper.exe). Therefore, its location will depend on where you installed PIX4Dmapper. For example, this could be: C:\Program Files\Pix4Dmapper
2. In Image directory, click Browse... and select the directory where the images are stored. Use PIX4Dtagger for one subproject at a time.
3. In Tags coordinates file, click Browse... and select the *.csv file in which the tags that were used in the project and their corners are stored. The file can be downloaded from here.
4. In the Camera models file, click Browse... and select the camera database in: C:\Users\Your Username\
5. In Output file, click Browse... and select the name of the output file and where it should be stored.
6. In Format, select PIX4D project file (*.p4d) and make sure that Export image geolocation and orientation is selected. PIX4Dtagger is able to compute exterior orientations based on the tag´s coordinates. These exterior orientations will be used as initial values during the standard PIX4D process and they will help in the reconstruction.
7. Click Start to start exporting the project file.
8. Repeat steps 1-7 for each dataset captured.
9. Click Close to close PIX4Dtagger.
Using PIX4Dmapper to process the subprojects
1. Open each of the subprojects generated in PIX4Dmapper by double-clicking it.
2. In the Processing Options of step 1. Initial Processing, in the Matching Image Pair section of the Matching tab, select Free Flight or Terrestrial: Menu Process > Processing Options... > 1. Initial Processing > Matching.
3. In the Processing Options of step 1. Initial Processing, in the Calibration tab, select Accurate Geolocation and Orientation calibration method:Menu Process > Processing Options... > 1. Initial Processing > Calibration.
4. In the Image Properties Editor window, edit the Accuracy Horz and Accuracy Vert values to 0.10 m. For more information: Menu Project > Image Properties Editor... > Images Table.
5. Process step 1. Initial Processing.
6. Repeat steps 1-5 for each subproject generated.
Using PIX4Dmapper to merge the subprojects
1. Clear the image geolocation of the images by clicking Clear in the Image Geolocation section of the Image Properties Editor: Menu Project > Image Properties Editor... > Image Geolocation.
2. Remove all GCPs of the visual markers from the subproject: GCP / Manual Tie Point Table.
3. Mark at least 3 Manual Tie Points in the common area between the subprojects. The common MTPs should share the same name in all the subprojects that they appear.
4. Repeat steps 1-3 for all subprojects.
5. Merge the subprojects following: Merging projects.
6. Process step 2. Point Cloud and Mesh for the merged project.
7. (optional) Edit the point cloud to remove the points of the visual marks reconstructed, following: How to edit the point cloud in the rayCloud.
8. (optional) Regenerate the 3D Textured Mesh without the visual marks, following: How to generate the 3D Textured Mesh (section: After processing step 2. Point Cloud and Mesh).
Hi, I'm using Pix4Dmapper pro and I want to make 3D model of scaffolding pipe which is long about 2~3.8m and thin(diameter is 8cm)
As you can see below because it is small and thin, long object(unusual case), it is not well constructed. I have 4 rotation for vertical direction(around curve surface), and horizontal overlap is much more than that. How can I improve accuracy of 3D model? is there any tips for that like using geographical location information or else?
Thank you so much.
Hi Hong JongHwa,
Indeed, it's a challenging project especially, that the object seems to have homogenous surface what always causes issues in photogrammetry reconstruction.
However, let's analyse the data and see what can be done to improve the 3D model.
Please share with us the Quality Report so we can investigate the project and give some advice.
Cheers!
Hi Beata,
I have been following the small object 3d reconstruction with pix4d for a while. I notice that, the software has been updated a lot, but the page with how to model small objects remians the same https://support.pix4d.com/hc/en-us/articles/218022823-How-to-model-small-objects .
I want to know if there area some break through in this thread.
Thank you very much.
Hi, Beata.
Thanks for your kind reply. There is some issue in my project as you see. I want some technical support. How can I share my data and Quality report?
We are scanning scaffold member which is long and thin, small object. The issues are like these.
1. adequate overlap (the number of required images that considers processing time - to be fast)
2. the actual size of the small object
- I measured the distance of the object in 3D dense point cloud, but it didn't fit the actual size.
Hi Hong. In order to get personal support please open a ticket by clicking "Contact Support" in the banner at the top of the page. Then include a relevant description of the issue along with a quality report and screenshots of the issue.
Hi, I've tried to use this tutorial tho Pix4Dtagger is no longer available. Do we can still modell small objects? I'm using a Canon 5D Mark III.
Currently, we do not offer the Pix4Dtagger. We removed it from the installation package of Pix4Dmapper version 4.6