# Leaky Analytic Sphere¶

## Executive Summary¶

Avoid doing tests that involve shooting millions of photons at points where bounding boxes touch geometry, OR enlarge bounding boxes by very small factors to avoid the touching.:

debug=1.000001


## Polar Leak¶

local torch_config=(
type=refltest
photons=500000
polz={pol}pol frame=1 source=0,0,300 target=0,0,0 radius=100 zenithazimuth=0,0.5,0,1 material=Vacuum ) local test_config=( mode=BoxInBox dimensions=500,300,0,0 shape=S,S boundary=Rock//perfectAbsorbSurface/Vacuum boundary=Vacuum///Pyrex analytic=1 ) Shooting millions of photons from Vacuum at the +Z pole of Pyrex sphere from a hemi-spherical torch source leads some 8% incorrectly thinking already in pyrex when actually in vacuum (ie rays failed to intersect at the targetted +Z pole outer surface instead intersecting all the way across on other side of sphere from “inside”) Select them interactively with material sequences starting Py: [2015-Nov-17 11:39:11.677236]:info: 3 24686 0.049 dde Py Vm Vm 5 10752 0.022 ee Py Py 10 979 0.002 ddee Py Py Vm Vm This is visible as a red Pyrex volcanic plume within the mostly white outside the sphere. The plume is centered around the normal direction but is fairly broad. The targetted point is special as thats along axis where the axis aligned bounding box touches the sphere. ## Scaling the BBox¶ Is the bbox effectively clipping the sphere leaving a hole for the photons to sneak thru ? YEP, seems so : scaling the bbox my a very small amount eliminates the problem, • zero/0.5M start with the wrong material Py debug=1.000001  ## Radial Shooting from all directions¶ Two concentic spheres of radii 500 and 300 mm with spherical torch of radius 400 mm with emitting in inwards radial direction (source=0,0,0). No signs of any leaking here, so not an issue with normal incidence. local torch_config=( type=refltest photons=500000 polz={pol}pol
frame=1
source=0,0,0
target=0,0,0
)