Variants: allow registering callbacks for variant changes

merlinND commented 3 weeks ago

Description

As discussed with @njroussel.

Currently, upon each variant change, we explicitly reload the custom Python integrators shipped in mitsuba.python.ad.integrators. Users don't have access to such a mechanism.

By allowing users to register callbacks, they can now implement module loading & reloading for their custom Python plugins. In the future, there may be a higher-level way for users to register plugins that will automatically create such a reload callback.

I also added an alias scoped_set_variant to variant_context so that it matches dr.scoped_set_flag().

Testing

Added a unit test check.

Checklist

[x] My code follows the style guidelines of this project
[x] My changes generate no new warnings
[x] My code also compiles for cuda_* and llvm_* variants. If you can't test this, please leave below
[x] I have commented my code
[x] I have made corresponding changes to the documentation
[x] I have added tests that prove my fix is effective or that my feature works
[x] I cleaned the commit history and removed any "Merge" commits
[x] I give permission that the Mitsuba 3 project may redistribute my contributions under the terms of its license

njroussel commented 3 days ago

I've added minor changes and rebased the branch.

Thanks @merlinND :+1:

merlinND commented 3 days ago

Sorry I was on holidays last week, thanks a lot for taking over @njroussel!

I had started with variant_change_callbacks as an nb::object but ended up downgrading it, I'm not sure why anymore. Probably I wasn't familiar enough with Nanobind to figure it out.

Edit: just saw your comment about nb::object vs nb::set, that must be what I ran into.

dvicini commented 3 days ago

Awesome, really nice addition!

mitsuba-renderer / mitsuba3