Wish: Support of LAZ (compressed LAS)?

[neteler]

It would be great if cloudbase could read LAZ directly - we have tons of LAZ files, but neither LAS nor the space to decompress them.

[phma]

I've thought about this. Since Wolkenbase reads LAS files in chunks, jumping around, I think the way to do this is to decompress a file, read the LAS file, then delete the LAS file. This means that at most as many decompressed files would be on disk at once as the program is running worker threads, which by default is the number of CPU threads.

If I add code to CMakeLists.txt to look for liblaszip, can you add code to decompress a LAZ file for the time it takes to read it? LasHeader::openRead would need to be modified to detect a LAZ file, and methods added to decompress it and delete the decompressed file.

[neteler]

I'm not really a CPP programmer but I'll ask around to find someone.

[phma]

I may find time to do it myself, but if you find someone, that's good too.

[phma]

I just got wolkentest to write some LAZ files.

[phma]

What should the program do if it's built without LASzip and you open a LAZ file? They won't appear in the directory listing if built without LASzip, but you could rename a LAZ file to LAS.

[neteler]

I'd simply exit with error: "file unreadable". If a user renames the file extension to something unsupported it may simply fail with an error message (I hope I understood what you meant).

[phma]

The user will interpret that as the program crashing. Not good.

Right now, if I try to open LAZ files, when I start the process, it spews out (to the console, not a popup window) lots of "Point out of range" messages followed by "Error reading file", but it doesn't exit. It's trying to read compressed data as if they were uncompressed, and when it reads a point past the end of file, it says "Error reading file". If you opened more files than there are threads, the thread would then try to read another LAZ file, with the same result. It sets a flag that the file is compressed, but doesn't do anything with that bit yet.

I just tried opening some files that aren't LAS or LAZ. When I opened them, it said "Reading file..." but didn't put any rectangles on the screen, because they have no LAS header. When I did "Save as is", it said "Keeping zeros" on some and "Dropping zeros" on others, but read in no points and didn't bother writing the output file because it had no points to write.

[phma]

It now reads LAZ files, but as I haven't changed the GUI, you have to select "All files" in the open dialog to see them. I haven't made it write LAZ files, except in the test program, as I'll have to change GUI code to do so. I'm going on a trip today and will hopefully get to that next week.

[neteler]

What should the program do if it's built without LASzip and you open a LAZ file? They won't appear in the directory listing if built without LASzip, but you could rename a LAZ file to LAS.

Just a remark on this: There is a mime-type application/vnd.las but I did not find any for LAZ.

[neteler]

It now reads LAZ files,

This is super cool!

but as I haven't changed the GUI, you have to select "All files" in the open dialog to see them.

I have compiled it on Fedora 36 but the "open" dialog button actually doesn't open a window. I have QT5.15.6 running here.

My test data are these (official federal state data):
https://www.opengeodata.nrw.de/produkte/geobasis/hm/3dm_l_las/3dm_l_las/

[phma]

When I do File|Open on the menu, it brings up a dialog box, and I can select files. If I then hit the Open button on the dialog box, the main window shows a rectangle, the bounding box, for each LAS or LAZ file I selected. What happens when you run it?

Sorry for the late response. I was at a campmeeting for Sukkot, and even if I had brought my laptop, which I didn't, connection was flaky.

[neteler]

When I do File|Open on the menu, it brings up a dialog box, and I can select files.

Not sure what happened but after a clean recompile "my" GUI behaves and the dialog is there so that I can open LAZ files.

Mhh, on a new run it stops again to open the dialog. There is no message in the terminal (from where I open wolkenbase), and ps aux also doesn't show anything. This time recompile didn't help. Unfortunately I have no idea how to debug this.

If I then hit the Open button on the dialog box, the main window shows a rectangle, the bounding box, for each LAS or LAZ file I selected. What happens when you run it?

I saw the LAZ files shown (I tried two). Then I ran the classifier via menu on it (nice ball moving around :-) )

Sorry for the late response. I was at a campmeeting for Sukkot, and even if I had brought my laptop, which I didn't, connection was flaky.

That's totally fine, I can wait without problems. Just wished to contribute more, but at least testing I can do.

[phma]

Can you explain step by step how to reproduce the bug? I don't know what you mean by "stops to open the dialog".

[neteler]

Earlier today I could open the File > Open dialog, now not any longer (no idea what has changed - no reboot, I just continued to work).

So I recorded a screencast:

[phma]

To debug that, run "gdb -p pidof wolkenbase" in another window. (Those are backticks. The preview renders them as monospaced, but you have to type backticks.) Then set a breakpoint at MainWindow::openFile and see what happens. If it doesn't break, check if openAction is triggered (I'm not sure how to do this).