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PSIntegrator: fix biased boundary gradients when sample_border is enabled #1954

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PSIntegrator: fix biased boundary gradients when sample_border is enabled #1954

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516e83a
``PSIntegrator``: fix boundary sample normalization
fknfilewalker Sep 8, 2026
591dc50
``PSIntegrator``: account for the filter border when culling
fknfilewalker Sep 8, 2026
b9351f0
``PSIntegrator``: splat boundary samples at the right pixel
fknfilewalker Sep 9, 2026
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15 changes: 10 additions & 5 deletions src/python/python/ad/integrators/common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1138,9 +1138,12 @@ def render_primarily_visible_silhouette(self,
block = film.create_block(normalize=True)
block.set_coalesce(block.coalesce() and spp >= 4)
block.put(
pos=sensor_ds.uv,
pos=sensor_ds.uv + mi.ScalarPoint2f(block.offset()),
wavelengths=wavelengths,
value=derivative * dr.rcp(mi.ScalarFloat(spp)),
# Boundary samples are not tied to pixels: normalize by their
# count and the pixel area, not by `spp`
value=derivative * (dr.prod(film.crop_size()) /
mi.ScalarFloat(sampler.wavefront_size())),
weight=0,
alpha=1,
active=active
Expand Down Expand Up @@ -1246,14 +1249,16 @@ def render_indirect_silhouette(self,
scene, sensor, sample, sampler, preprocess=False)
active = dr.any(value != 0)

# Account for the guiding sampling density and spp
value *= rcp_pdf_guiding * dr.rcp(spp)
# Account for the guiding density, the sample count and the
# pixel area
value *= rcp_pdf_guiding * (dr.prod(film.crop_size()) /
mi.ScalarFloat(sampler.wavefront_size()))

# Splat the result to the film
block = film.create_block(normalize=True)
block.set_coalesce(block.coalesce() and spp >= 4)
block.put(
pos=sensor_uv,
pos=sensor_uv + mi.ScalarPoint2f(block.offset()),
wavelengths=wavelengths,
value=value,
weight=0,
Expand Down
12 changes: 11 additions & 1 deletion src/python/python/ad/projective.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,7 +175,17 @@ def eval_primary_silhouette_radiance_difference(self,
it = dr.zeros(mi.Interaction3f)
it.p = ss.p
ds, _ = sensor.sample_direction(it, mi.Point2f(0), active)
visible &= ds.pdf != 0
film = sensor.film()
if film.sample_border():
# The filter reaches past the crop window, so points just
# outside of it still contribute
border = film.rfilter().border_size()
size = mi.ScalarVector2f(film.crop_size())
in_front = (to_world.inverse() @ ss.p).z > 0
visible &= in_front & dr.all((ds.uv >= -border) &
(ds.uv <= size + border))
else:
visible &= ds.pdf != 0

# Sample wavelengths
wavelength_sample = 0
Expand Down