Loading of `*.pcd` point clouds ignores decimals after initializing PyQt's QApplication

[ch-sa]

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for master branch).

Describe the issue

I am trying to load a *.pcd point cloud that contains float positions within a PyQt application. When loading the point cloud using o3d.io.read_point_cloud() the points are rounded integers and Open3D ignored the decimal places, which do exist inside the file.

I tracked the bug to only happen after initializing the PyQt application with QApplication(sys.argv). Trying to load the point cloud outside the PyQt application (e.g. in ipython) works fine.

So I assume there must be an interdependence between Open3D and PyQt.

I reproduced this bug with a point cloud provided by sb. issuing this problem for my point cloud labeling tool here: ch-sa/labelCloud#68.
The point cloud was provided here: https://github.com/ch-sa/labelCloud/files/8345198/pointcloud_116.zip.

PyQt-Versions:

$ conda list | grep qt
pyqt5                     5.15.4                   pypi_0    pypi
pyqt5-qt5                 5.15.2                   pypi_0    pypi
pyqt5-sip                 12.9.0                   pypi_0    pypi
pytest-qt                 4.0.2                    pypi_0    pypi

Steps to reproduce the bug

import sys

from PyQt5.QtWidgets import QApplication

import open3d as o3d

QApplication(sys.argv)

pcd = o3d.io.read_point_cloud("pointcloud_116.pcd")
print(f"First point: {pcd.points[0]}")

Error message

First point: [-0. 11. 0.]

Expected behavior

A loaded point cloud with floats:

First point: [-0.20108423 11.055668    0.56653374]

This is the case when I comment QApplication(sys.argv) out.

Open3D, Python and System information

- Operating system: Distro: Linux Mint 20.3 Una base: Ubuntu 20.04 focal
- Python version: 3.8.11 (default, Aug  3 2021, 15:09:35) [GCC 7.5.0]
- Open3D version: 0.15.2
- System architecture: x86
- Is this a remote workstation?: no
- How did you install Open3D?: pip (inside conda)

More details can be found here: https://termbin.com/n0go

Additional information

The issue did not appear so far when loading other point cloud formats.