Given a scene and a shape, how to know the bsdf(s) is specular or not?

[Mephisto405]

scene = mi.load_file("data/cornell-box/scene_v3.xml")
print(scene.shapes()[5].bsdf()
""" The above code returns:
TwoSided[
  brdf[0] = SmoothDiffuse[
    reflectance = SRGBReflectanceSpectrum[
      value = [[0.725, 0.71, 0.68]]
    ]
  ],
  brdf[1] = SmoothDiffuse[
    reflectance = SRGBReflectanceSpectrum[
      value = [[0.725, 0.71, 0.68]]
    ]
  ]
]
"""

In the above code snippet, the sixth shape in the scene has only diffuse BSDF. In this case, I want a method that returns False.
If the BSDF is specular (or other 'Dirac delta' distributions), the method should return True.
Overall, the question is about how to access the 'type' of a BSDF.

One way might be to use the repr() function.
But I wonder whether there is another way to do that (using some built-in Mitsuba function).

[njroussel]

Hi,

I think you're looking for the BSDF.flags() method: BSDF.flags. And these are the individual flag/types supported: mitsuba.BSDFFlags. You will usually want to use a combination of these with: mitsuba.has_flag.

Here's an example where we use it.

[Mephisto405]

OMG, it was so easy! Thx very much.
I didn't understand the purpose and use of flags by just looking at the documentation, but now I understand properly.
Many thanks!

[njroussel]

Yes, the documentation isn't very clear 😅, I'll add that to our to-do list.