[hn-cso]

To reproduce:Place a camera in a scene and point it at a 30x50x10 mm block (attached). Take a depth image of it with:

Code:

from robodk import robolink
import numpy as np
import os
import time
RDK = robolink.Robolink()

# Get depth snapshot
cam = RDK.Item('Depth Camera')
cam.setParam('Open')
time.sleep(0.1)
RDK.Cam2D_Snapshot(os.path.join(os.path.abspath('.'), 'tmp.grey32'), cam, 'Depth')
grey32 = np.fromfile('tmp.grey32', dtype='>u4')
w, h = grey32[:2]
img = np.flipud(np.reshape(grey32[2:], (h, w)))
img = (img / np.iinfo(np.uint32).max) # rescale to float 0.0 to 1.0
FAR_LENGTH = 100 # whatever FAR_LENGTH is set to
img = img * FAR_LENGTH
img = img.astype(np.uint16)

# Save as pointcloud with open3d
import open3d as o3d
FOV = 63.91 # whatever FOV is set to
fy = h / (2*np.tan(np.radians(FOV) / 2)) # FOV is camera field of view
内在= o3d.camera.PinholeCameraIntrinsic (
width=w,
height=h,
fx=fy, # Use same value for fx and fy
fy=fy,
cx=w / 2,
cy=h / 2,
)

pcd = o3d.geometry.PointCloud.create_from_depth_image(o3d.geometry.Image(img), intrinsic)
o3d.io.write_point_cloud('pcd.xyz', pcd, write_ascii=True)

Open the resulting pcd.xyz file with MeshLab or your pointcloud viewer of choice.

Expected result:the resulting pointcloud is a rectangular block and has dimensions 30x50x10.

Actual result:the resulting pointcloud does not have dimensions 30x50x10 and has angles that are not 90 degrees.

Fixing z-distortion:if I insert the following line just after normalizing img to be between 0 and 1:

Code:

img = img / (2 - img)

then the resulting pointcloud has correct dimensions. Note that the transformation above takes 0 to 0 and 1 to 1 and takes straight lines and flat planes to straight lines and flat planes, but distorts distances and angles. Maybe someone inserted some sort of gamma correction somewhere?