the reverse-mode derivative of a complex loop support

mitsuba-renderer / mitsuba3

Mitsuba 3: A Retargetable Forward and Inverse Renderer

https://www.mitsuba-renderer.org/

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the reverse-mode derivative of a complex loop support #1321

Closed andyyankai closed 1 month ago

andyyankai commented 1 month ago

I am running the latest prbvolpath for the main branch, but see the following error in backward.

Traceback (most recent call last):
  File "C:\xxx\mitsuba\python\ad\integrators\prbvolpath.py", line 271, in _loop_body
    dr.backward(δL * contrib)
RuntimeError: CustomOp::backward(): the reverse-mode derivative of a complex loop (with max_iterations != -1) is not yet implemented!

Is dr.loop still under development can we cannot run prb integrator now? is there an estimated time? Thanks!

andyyankai commented 1 month ago

it seems the issue only happen for the loop in transmittion evalution when using NEE (another loop in rendering loop)

njroussel commented 3 days ago

Sorry, for the lack of answer. For posterity, this was fixed in https://github.com/mitsuba-renderer/mitsuba3/commit/5095669ad7cd1cef1cad4f1d01fad9a2060946b7.