Get coordinates in point of cloud.

[amartincirera]

Hello,

I am currently working with the RealSense D435i camera, and I am interested in finding out if there is a way to retrieve the pixel positions of the camera or the 2D coordinates once the data has been exported to the 'ply' format. In other words, I would like to establish the correspondence of a specific point in the point cloud with its 2D coordinates.

I am using the example provided in export_ply_example.py to export the data to the ply format.

Thank you very much for your assistance.

[MartyG-RealSense]

Hi @amartincirera Once a ply file has been created then it can be imported into 3D modelling software such as MeshLab, Blender and CloudCompare.

https://www.meshlab.net/

https://www.andreasjakl.com/capturing-3d-point-cloud-intel-realsense-converting-mesh-meshlab/

The ply data cannot be imported directly back into the RealSense SDK once exported though, unfortunately. A workaround may be to use the SDK's support for integration with PCL (Point Cloud Library) to read the ply file using PCL code. An example of such an instruction is pcl::io::loadPLYFile()

https://pointclouds.org/documentation/group__io.html#ga81c8bb6bf8c94fd68301f2b8e863e56f

[amartincirera]

Thank you very much for the quick response @MartyG-RealSense.

When exporting to PLY format, does the corresponding information of a point in 2D coordinates (pixel position) remain preserved? In that case, using the PCL library could be an option.

The issue is that I am annotating point of cloud with CVAT, a tool for annotating images, videos, point clouds, and more. When I export the annotations, it returns the following:

tx: -0.05
ty: 0.21
tz: -0.65

The 'x' and 'y' coordinates do not correspond to the positions of the pixels in the original images before exporting to PLY.

Thank you very much!

[MartyG-RealSense]

A ply file contains 'property float x', 'property float y' and 'property float z'.

https://en.wikipedia.org/wiki/PLY_(file_format)

This is demonstrated in the contents of a RealSense ply file shown at #3835 (comment)

A 3D pointcloud represents 3D XYZ values in the real-world rather than 2D image pixel values.