simGetLidarSegmentation() do not match getLidarData().point_cloud

[xiaoaoran]

I tried to get segmentation ground truth via client.simGetLidarSegmentation():

lidarData = self.client.getLidarData()
lidarSeg = self.client.simGetLidarSegmentation()

print(len(lidarData.point_cloud))
>>>3858
print(len(lidarSeg))
>>>1336
So the number of lidar point in lidarData should be 3858/3=1286, which is not equal to the number of ground truth points in lidarSeg

but @ironclownfish said

api function: simGetLidarSegmentation().
Returns the segmentation of each lidar point's collided object in the last lidar update. i.e. the segmentation IDs align with getLidarData().point_cloud
https://github.com/microsoft/AirSim/pull/2011#issue-286773742

Anyone could tell me why? Thanks!

[TheFloe1995]

I also stumbled across this issue. It seems that you have to call both functions right after each other.

In a quick experiment I called both functions directly after each other at 10 FPS while moving. Most of the time the number of points was equal in both lists. But in 7/300 cases they were different.

Seems to be timing dependent which is quite inconvenient in my opinion. Are there any plans to change that behaviour, e.g. having a single function call to get the point cloud + segmentation IDs?

[rajat2004]

I've opened #2810 which combines segmentation data into LidarData struct fetched using getLidarData