Which integrator should I use if I want to deal with transparent object?

[ChauChorHim]

Hi, I have some images of a transparent object captured in a darkroom and the only light source is a LCD screen with some patterns. I want to leverage the loss between these captured images and mitsuba rendered images to optimize the shape of transparent object. The question is thata 'path' integrator which seems not support to produce gradients of images with respect to the transparent object vertex positions. 'prb_reparam' and 'ptracer' are also not suitable for a transparent object (not a slab like the tutorial of caustics optimization). Could you please tell me which integrator is fitted my requirements? Thanks :)

[ziyi-zhang]

Hi @ChauChorHim,
That reminds me of this research and a few related ones.
Assuming you are applying Mitsuba in their setup: homogenous glass, triangle mesh object, LCD patterned screen (we may be able to lift the constraint that a ray only interacts twice),

• prb won't be necessary as the light path is short.
• reparam is useless in this setting as we don't have occlusion driven discontinuity.
• ptracer must be used in the caustic design because we have a directional emitter. Since you have a LCD monitor, this is no longer mandatory.
• path (the version in path.cpp) is a detached estimator. As you said, only the eval_pdf is attached to the autodiff tape.

Depending on your experiment setup, in my opinion, ptracer or a custom attached path might (I am not certain though =) ) be enough.

[ChauChorHim]

Hi Ziyi,

Thanks for your quick reply and detailed explanation. I will try to use ptracer then.

P.S. It is this paper you mentioned I am following now.