PCDReader: remove fields with zero count instead of throwing exception while reading

[shreysamdani]

Description

For LIDAR pcd files, there can be instances where the count for a field is < 1 if the field is "_". In such cases, we shouldn't throw an error when trying to read the file.

Bugs resolved

PDAL/PDAL#2572

[mvieth]

Hi, sorry for the delay.
I am not so sure about this code change. I feel like we might introduce bugs if we allow point fields with count < 1 (even if they are only "_" fields). Do you know how these LIDAR PCD files were created? The PCDWriter from PCL won't write fields with count=0.
BTW a solution to "fix" such PCD files would be to remove the columns from the PCD header (remove the respective entries in FIELDS, SIZE, TYPE, COUNT).

[weimzh]

same issue here.
many PCD files provided by our client won't work due to this.

.PCD v0.7 - Point Cloud Data file format

VERSION 0.7
FIELDS x y z _ intensity _ timestamp _ ring _
SIZE 4 4 4 1 4 1 8 1 2 1
TYPE F F F U F U F U U U
COUNT 1 1 1 4 1 0 1 6 1 12
WIDTH 93504
HEIGHT 1
VIEWPOINT 0 0 0 1 0 0 0
POINTS 93504
DATA binary

[kunaltyagi]

Instead of modifying the core lib, how about a tool to remove 0 count fields?

[mvieth]

Or how about changing the PCDReader so that these fields are removed during reading, as if they had never been in the PCD file?

[kunaltyagi]

😆 Didn't realize this was not an issue, but a single line PR

[kunaltyagi]

Instead of moving ahead with a 0 count, should we be using erase+remove on cloud.fields[i]? (either here or after reading the header)

[xaedes]

This is still an issue in 2022. Will that PR be merged?

[mvieth]

This is still an issue in 2022. Will that PR be merged?

Not with the changes it makes right now. Copied from my earlier comment:

I am not so sure about this code change. I feel like we might introduce bugs if we allow point fields with count < 1 (even if they are only "_" fields). Do you know how these LIDAR PCD files were created? The PCDWriter from PCL won't write fields with count=0.
BTW a solution to "fix" such PCD files would be to remove the columns from the PCD header (remove the respective entries in FIELDS, SIZE, TYPE, COUNT).

[mvieth]

I will merge this in a few days if there are no objections