Shooting millions of photons at triangulation edges is fount to let some thru. The solution is to avoid doing that eg by shifting targetted point to avoid cracks or use analytic box instead.
BoxInBox Pyrex block in Vacuum lit by spherical focus light targetting single point:
ggv.sh --test --save \
--eye 0.5,0.5,0.0 \
--animtimemax 7 \
--testconfig "mode=BoxInBox_dimensions=500,300,0,0_boundary=Rock//perfectAbsorbSurface/Vacuum_boundary=Vacuum///Pyrex_" \
--torchconfig "polz=spol_frame=1_type=refltest_source=0,0,300_target=0,0,1_radius=102_zenithazimuth=0,0.5,0,1_material=Vacuum" \
$*
Rec.py seqhis selection
Some 6 percent miss the target:
In [78]: pos1[:,2]
Out[78]: array([ 299.997, 299.997, 299.997, ..., 299.997, 299.997, 299.997], dtype=float32)
In [91]: pos1[pos1[:,2] != pos1[0,2]].shape
Out[91]: (4728, 3)
In [82]: p1z
Out[82]: array([ 299.997, 299.997, 299.997, ..., 299.997, 299.997, 299.997], dtype=float32)
In [83]: p1z[p1z<299]
Out[83]: array([ 12.009, 47.792, -18.876, ..., -15.503, -42.802, 68.941], dtype=float32)
In [87]: 4728./82600
Out[87]: 0.05723970944309927