installation problem

[DreadInside]

I tried installing the plugin on Blender 4.2.1 LTS, but when I try to activate it, I get the error:
No module named 'numpy._core'

[DreadInside]

during installation it shows this

I saw a similar comment on YouTube where someone said they reinstalled NumPy, but I don't understand what that means. Mean inside Blender or do need to install the numpy library separately in Python?
I have Python installed and added to my Path. I tried reinstalling NumPy, but it didn't work.

[CodeFHD]

Yes, this has been encountered before. I still think this can not be caused by OptiCore itself, as it only uses numpy but does not meddle with its installation.

First: Blender includes its own python environment, so as you noticed yourself, installing it in a separate python environment has no effect.

Now, I have seen this error myself but because of another reason: Installing and then uninstalling another extension that does something to numpy.
Specific example: LuxCoreRender, where I do some development and frequently install and uninstall it for testing purposes. Sometimes, uninstalling LuxCoreRender leaves numpy broken, sometimes not. So if you uninstalled other extensions at some point, this may be the reason.

I'm not sure what the best cause of action is for you:
You can try to reinstall Blender, with or without cleaning the User Directories (https://docs.blender.org/manual/en/latest/advanced/blender_directory_layout.html) depending on how many custom settings and extension installations you need to preserve.
Perhaps there are also some numpy files left from such a previous installation. The path to this, in the user directories, would be something like blender/4.2/extensions/.local/lib/python3.11/site-packages

[DreadInside]

The thing is, I downloaded the new Blender from the website and immediately installed OptiCore, but I also have other versions, including from Steam. Could the problem be with the system files on the C drive? I'm not very knowledgeable about programming, but judging by the error I showed in the second screenshot, isn't it possible to determine the root of the problem? I couldn't select or copy the text of this traceback, and I'm having trouble understanding all the dependencies between all the modules.
In any case, the numpi module should be there, and isn't OptiCore calling it, judging by the report?

Oh, I finally figured out how to display the error text separately.
So, I deleted the user settings in AppData\Roaming\Blender Foundation\Blender
just in case, and also re-unzipped the clean Blender 4.2.1 portable version.

Regarding the path
blender/4.2/extensions/.local/lib/python3.11/site-packages
is this in Blender's working directory? If so, my path ends in "extensions," and there's only a readme.txt file there.
I also tried removing the path to Python from the Windows environment variable.
but the result is the same

[CodeFHD]

Okay, I tried to reproduce the issue by deleting my 4.2 installation + configs and could reproduce the issue!

I may have found the reason after reading around a bit about this numpy error and found this thread: https://www.reddit.com/r/learnpython/comments/1dnzcpi/no_module_numpy_core_i_need_urgent_help/

OptiCore contains some catalog data stored in pickle format, and my error log does show the problem happening at this point.

I also tested with Blender 4.4 and the issue does not show up there. Blender 4.2 comes with numpy version 1.24, while 4.4 bundles 1.26. And indeed, there seems to have been a break at version 1.26! numpy/numpy#24844

I should perhaps reconsider the use of the pickle format for storing the data, but I don't expect it will be done quickly.

Do you need to stay on Blender 4.2 for LTS reasons? Version 4.5 is also LTS, perhaps you can switch?
If you do have to stay on version 4.2, I still suggest to install a bugfix release, as version 4.2.16 is the latest and you are still using 4.2.1!

There is also the possibility to install a newer numpy into Blender, I would refer you to other guides how to do this:
https://stackoverflow.com/questions/11161901/how-to-install-python-modules-in-blender
(I never noticed the Issue in 4.2 because I always had a separate numpy installed due to LuxCore)

[DreadInside]

I just wanted to find something for testing geometric optics like Zemax, but with a decent interface, so I don't care which version I use. I just figured since OptiCore is a newer project, I should use it, since I didn't want to install Blender, which is too old for LuxeCore

Basically, the main thing for me is that it works.

So, I checked, and everything started working for me on version 4.4.3.
thanks

P.S.
This is my first time using this form on GitHub. Should I close the issue myself or can you do it yourself?😅

P.P.S
It might be worth changing this line so that new users are aware of the instability of the version?