Easiest way to edit arbitrary scene parameters in Python

[treder]

What is the easiest way to edit a scene without touching the XML file? For instance if I load the bathroom scene

scene = mi.load_file(data_dir + 'bathroom/scene.xml')
print(scene)

I get

Scene[
  children = [
    PathIntegrator[
      max_depth = 17,
      rr_depth = 5
    ],
    PerspectiveCamera[
      x_fov = [55],
      near_clip = 0.01,
      far_clip = 10000,
      film = HDRFilm[
        size = [1024, 1024],
        crop_size = [1024, 1024],
        crop_offset = [0, 0],
        sample_border = 0,
        compensate = 0,
        filter = TentFilter[radius=1.000000],
        file_format = OpenEXR,
        pixel_format = rgb,
        component_format = float16,
      ],
      sampler = IndependentSampler[
        base_seed = 0
        sample_count = 64
        samples_per_wavefront = 1
        wavefront_size = 0
      ],
      resolution = [1024, 1024],
      shutter_open = 0,
      shutter_open_time = 0,
      to_world = [[-0.659198, 0.0116337, -0.751879, 0.00724053],
                  [0, 0.99988, 0.015471, 0.912405],
                  [0.751969, 0.0101985, -0.659119, -0.227584],
                  [0, 0, 0, 1]]
    ],
......

I want to change the film filter. The obvious approach is params = mi.traverse(scene.sensors()[0].film()) and then edit filter, but it is not possible since the only parameters it returns are

SceneParameters[
  ------------------------------------------------------------------
  Name           Flags    Type           Parent
  ------------------------------------------------------------------
  size                    ScalarVector2u HDRFilm
  crop_size               ScalarVector2u HDRFilm
  crop_offset             ScalarPoint2u  HDRFilm
]

params['filter'] is not available and cannot be set. How can I redefine the filter and keep everything else as it is?

[njroussel]

Hi @treder

We don't provide any utilities for such changes currently. The mi.traverse() function is only useful for tuning parameters of a plugin, not changing entire plugins.

I have personally found it convenient to use a Python XML parser to extract the tree from the file, modify it, write it a new temporary file and then mi.load_file this temporary file.

[treder]

OK, thank you for the quick answer.