Different result export_to_ply vs np.asanyarray(points.get_vertices())

[drapado]

Required Info
Camera Model	L515
Firmware Version	01.05.05.00
Operating System & Version	Ubuntu 20.04
Kernel Version (Linux Only)	5.11.0-7614
Platform	PC
SDK Version	2.45
Language	python
Segment	others

I get different pointclouds when I used points.export_to_ply against np.asanyarray(points.get_vertices()).view(np.float32).reshape(-1, 3). I use the following code:

xyz_img = (
    np.asanyarray(points.get_vertices()).view(np.float32).reshape(-1, 3)
)
# Pass xyz to Open3D.o3d.geometry.PointCloud and visualize
pcd_0 = o3d.geometry.PointCloud()
pcd_0.points = o3d.utility.Vector3dVector(xyz_img)
pcd_0.paint_uniform_color([0, 1, 0]) # Green

points.export_to_ply(filename + ".ply", color_frame)
pcd = o3d.io.read_point_cloud(filename + ".ply")
pcd.paint_uniform_color([1, 0, 0]) # Red

o3d.visualization.draw_geometries([pcd, pcd_0])
xyz_load = np.asarray(pcd.points)
print(xyz_img.mean(axis=0), xyz_load.mean(axis=0))
# print output:
# [-0.02074947 -0.00784179  0.6535316 ] [-0.02128658  0.00804392 -0.66972431]

Visualization output:

Why does points.export_to_ply kind of invert Y and Z axes?

[MartyG-RealSense]

Hi @drapado Do you still require assistance with the problem in this case please? Thanks!

[drapado]

Hi @MartyG-RealSense yes if possible! I'd like to understand why the pointclouds are inverted when exporting to ply using pyrealsense2.
Thanks! :D

[MartyG-RealSense]

Hi @drapado I located another example in the link below of Y and Z being exported when using export_to_ply. In that case, C++ language and a D435i stereo depth model was being used instead of Python and L515 lidar camera.

https://programmersought.com/article/80301367145/

It may be related to how RealSense cameras observe a scene by looking outward like a human eye, so the perspective would not be the same as when looking towards the camera from a position in front of it.

There is an alternative method of exporting a ply called save_to_ply that you could test. The RealSense SDK has a Python example program called export_ply_example that uses this method.

https://github.com/IntelRealSense/librealsense/blob/master/wrappers/python/examples/export_ply_example.py

save_to_ply also offers a greater range of options for customizing the ply export by enabling and disabling certain features.

#4906

[MartyG-RealSense]

Hi @drapado Do you require further assistance with this case, please? Thanks!

[drapado]

@MartyG-RealSense Thanks a lot for your answer, quite clarifying! I don't require further assistance. Closing the issue :)

[MartyG-RealSense]

That's excellent to hear @drapado - thanks for the update!