title: open3d voxel_size too small : down sampling not working for e57 binaries
body: <p>I'm trying to downsample a point cloud. I have 2 data formats for different parts of my data.
  The .bin files cause no problems, but when I'm trying to downsample the .e57 files I encounter a strange problem.
  Here's what I do:</p>
  <pre><code>import numpy as np
  import open3d
  
  pointfile = &quot;path/to/file.e57&quot;
  pcd_data = np.fromfile(point_file, dtype=np.float32)
  pcd_data = velo_data.reshape(-1, 4)
  pcd_points = velo_data[:, :3]
  
  pcd = open3d.geometry.PointCloud()
  pcd.points = open3d.utility.Vector3dVector(pcd_points)
  pcd_down = pcd.voxel_down_sample(voxel_size=0.8)
  res = np.asarray(pcd_down.points)
  </code></pre>
  <p>It works fine for .bin, but when i try the .e57 I get the error:</p>
  <pre><code>RuntimeError: [Open3D ERROR] [VoxelDownSample] voxel_size is too small.
  </code></pre>
  <p>No matter if I use voxel_size of 0.005, 0.8, 100, 5000 or 1000000000000000.</p>
  <p>I tried the earlier open3d Version:</p>
  <pre><code>pcd_down = open3d.geometry.voxel_down_sample(voxel_size=0.8)
  </code></pre>
  <p>and at least it throws no error, but my downsampled pointcloud then contains 0 points (from ~350 000).</p>
  <p>As the file should be structured in points with 4 features, the file seems to be read correctly (this works for any of my files), as the reshape works just fine.</p>
  <p>Any ideas?</p>