Seek help! I would like to know the correct way to use "karma point read" in materials。I've tried a lot of things, but nothing worked。

I found the reason. The error is that the "$F" used when reading a file is not recognized. How should it be solved?For example：$HIP/Desktop/test/test/test.$F.bgeo.sc,You can't use "$F"...

This is expected behavior.

You can do it like this: Put a generic file name into the point cloud file parameter, like pcloud.0001.bgeo.sc

Append a edit material properties LOP after your material library.
Point its primpattern to your point cloud reader primitive, for example /materials/karmamaterial/kma_pcread1/

Press the "Create parameters" button, the parameters of that primitive will now appear underneath and can be modified.

Modify the point cloud file parameter to include the frame token, like pcloud.$F4.bgeo.sc

If you look at it in the geometry spreadsheet, you can now see that when you move on the timeline it will correctly update the primitive parameter.

A simplistic example file is attached.