[🐛 bug report] weight differentiation for blended BSDFs dysfunctional #381
Description
Summary
Computing an inverse rendering on blended BSDFs weight parameter yields false results.
System configuration
- Platform: Ubuntu 20.04.2 LTS (GNU/Linux 5.4.0-65-generic x86_64)
- Python version: Python 3.8.5
- Mitsuba2 version: commit fe2a1bd
Description
When trying to recover the bsdf type on a simple scene composed of two rectangles with different bsdf, the objective value increases instead of decreasing. The algorithms converges towards an image that seems inverted.
I tried clipping the weights between [0, 1] but it didn't help.
Related
I noticed @LeonidMill asked a question about this in issue #26. I read the follow-up recommendations through PRs #44 & #157 but was told by @Speierers this was unrelated.
Steps to reproduce
run attached file
rectangle_blended_weight_differentiation.zip