Lattice geometries cause a segmentation fault

[nuclearkevin]

When I plot models containing lattice geometries a segmentation fault (preceded by a collection of Lost particle after reflection. errors) gets thrown. This only appears to happen when disabling material views which expose lattice elements.

Steps to reproduce:

1. Launch the renderer with the provided model.xml.
2. Disable viewing of material 15.

[nuclearkevin]

<?xml version='1.0' encoding='utf-8'?>
<model>
  <materials>
    <material id="5" name="Helium" temperature="300">
      <density units="g/cc" value="0.0015981"/>
      <nuclide name="He3" wo="1.507034605870082e-06"/>
      <nuclide name="He4" wo="0.9999984929653941"/>
    </material>
    <material id="6" name="Inconel 718" temperature="300">
      <density units="g/cc" value="8.2"/>
      <nuclide name="Si28" wo="0.0032155731048992865"/>
      <nuclide name="Si29" wo="0.00016911126024752386"/>
      <nuclide name="Si30" wo="0.00011531563485318948"/>
      <nuclide name="Cr50" wo="0.007913309836673921"/>
      <nuclide name="Cr52" wo="0.15869399101815182"/>
      <nuclide name="Cr53" wo="0.01834112060820815"/>
      <nuclide name="Cr54" wo="0.004651578536966124"/>
      <nuclide name="Mn55" wo="0.0087"/>
      <nuclide name="Fe54" wo="0.016163233191609727"/>
      <nuclide name="Fe56" wo="0.26311407689588734"/>
      <nuclide name="Fe57" wo="0.0061851353409504845"/>
      <nuclide name="Fe58" wo="0.0008375545715524964"/>
      <nuclide name="Ni58" wo="0.3439850534132437"/>
      <nuclide name="Ni60" wo="0.13706615408115613"/>
      <nuclide name="Ni61" wo="0.00605761515763386"/>
      <nuclide name="Ni62" wo="0.019630455371550823"/>
      <nuclide name="Ni64" wo="0.0051607219764155535"/>
    </material>
    <material id="7" name="Zircaloy 4" temperature="300">
      <density units="g/cc" value="6.55"/>
      <nuclide name="O16" wo="0.001249496518284918"/>
      <nuclide name="O17" wo="5.034817150822443e-07"/>
      <nuclide name="Cr50" wo="4.173686622718313e-05"/>
      <nuclide name="Cr52" wo="0.000836993623513459"/>
      <nuclide name="Cr53" wo="9.673586818675183e-05"/>
      <nuclide name="Cr54" wo="2.4533642072606143e-05"/>
      <nuclide name="Fe54" wo="0.00011855672267684395"/>
      <nuclide name="Fe56" wo="0.0019299321043708116"/>
      <nuclide name="Fe57" wo="4.5367740887167366e-05"/>
      <nuclide name="Fe58" wo="6.143432065177235e-06"/>
      <nuclide name="Zr90" wo="0.4975030719418411"/>
      <nuclide name="Zr91" wo="0.10970127724609834"/>
      <nuclide name="Zr92" wo="0.1695240925103877"/>
      <nuclide name="Zr94" wo="0.1755385702549024"/>
      <nuclide name="Zr96" wo="0.02888298804677048"/>
      <nuclide name="Sn112" wo="0.00013258696500899892"/>
      <nuclide name="Sn114" wo="9.18244938630758e-05"/>
      <nuclide name="Sn115" wo="4.771905899254868e-05"/>
      <nuclide name="Sn116" wo="0.0020584231441515095"/>
      <nuclide name="Sn117" wo="0.0010966473380910862"/>
      <nuclide name="Sn118" wo="0.003487981278597598"/>
      <nuclide name="Sn119" wo="0.0012475771051862219"/>
      <nuclide name="Sn120" wo="0.004771539508846636"/>
      <nuclide name="Sn122" wo="0.000689409486231945"/>
      <nuclide name="Sn124" wo="0.0008762916210303822"/>
    </material>
    <material depletable="true" id="13" name="Fuel 3.4%" temperature="300">
      <density units="g/cc" value="10.35917"/>
      <nuclide ao="1.9992420000000009" name="O16"/>
      <nuclide ao="0.0007580000000000003" name="O17"/>
      <nuclide ao="0.0003081777486902833" name="U234"/>
      <nuclide ao="0.03447895446483311" name="U235"/>
      <nuclide ao="0.9650549376142341" name="U238"/>
      <nuclide ao="0.00015793017224252458" name="U236"/>
    </material>
    <material id="15" name="Borated Water" temperature="300">
      <density units="g/cc" value="0.7405820675158279"/>
      <nuclide ao="0.00032178660441590807" name="B10"/>
      <nuclide ao="0.001301758322001388" name="B11"/>
      <nuclide ao="1.9964419358489391" name="H1"/>
      <nuclide ao="0.0003109742982263195" name="H2"/>
      <nuclide ao="0.9979980703971097" name="O16"/>
      <nuclide ao="0.0003783846764728878" name="O17"/>
      <sab name="c_H_in_H2O"/>
    </material>
    <material id="16" name="Water SPN">
      <density units="g/cc" value="0.9810025319057221"/>
      <nuclide ao="0.00032178660441590807" name="B10"/>
      <nuclide ao="0.001301758322001388" name="B11"/>
      <nuclide ao="1.9964419358489391" name="H1"/>
      <nuclide ao="0.0003109742982263195" name="H2"/>
      <nuclide ao="0.9979980703971097" name="O16"/>
      <nuclide ao="0.0003783846764728878" name="O17"/>
      <sab name="c_H_in_H2O"/>
    </material>
    <material id="17" name="SS SPN" temperature="300">
      <density units="g/cc" value="3.6838480704877297"/>
      <nuclide name="Si28" wo="0.005512411036970206"/>
      <nuclide name="Si29" wo="0.00028990501756718373"/>
      <nuclide name="Si30" wo="0.00019768394546261053"/>
      <nuclide name="Cr50" wo="0.007930004583164795"/>
      <nuclide name="Cr52" wo="0.1590287884675572"/>
      <nuclide name="Cr53" wo="0.01837981495548285"/>
      <nuclide name="Cr54" wo="0.004661391993795167"/>
      <nuclide name="Mn55" wo="0.02"/>
      <nuclide name="Fe54" wo="0.03861561824331489"/>
      <nuclide name="Fe56" wo="0.6286064568522073"/>
      <nuclide name="Fe57" wo="0.014776921317534514"/>
      <nuclide name="Fe58" wo="0.0020010035869434425"/>
      <nuclide name="Ni58" wo="0.0671977052965899"/>
      <nuclide name="Ni60" wo="0.026775962899229563"/>
      <nuclide name="Ni61" wo="0.0011833590852967102"/>
      <nuclide name="Ni62" wo="0.0038348223034871697"/>
      <nuclide name="Ni64" wo="0.00100815041539667"/>
    </material>
  </materials>
  <geometry>
    <cell id="1" material="6" name="Fuel Spring" region="-18" universe="7"/>
    <cell id="2" material="5" name="Fuel Spring Gap" region="18 -17" universe="7"/>
    <cell id="3" material="13" name="Fuel" region="-15" universe="4"/>
    <cell id="4" material="5" name="Fuel Gap" region="15 -16" universe="4"/>
    <cell id="5" material="7" name="Fuel Clad" region="16 -17" universe="4"/>
    <cell id="6" material="15" name="Fuel Grid Water" region="17 1 -2 3 -4" universe="6"/>
    <cell id="7" material="15" name="Fuel Grid Water" region="17 5 -6 7 -8" universe="5"/>
    <cell id="8" material="6" name="Fuel Grid Inc" region="(-5 | 6 | -7 | 8) (9 -10 11 -12)" universe="5"/>
    <cell id="9" material="7" name="Fuel Grid Zr" region="(-1 | 2 | -3 | 4) (9 -10 11 -12)" universe="6"/>
    <cell id="11" material="7" name="Zr Pin" region="-17" universe="3"/>
    <cell id="12" material="15" name="Water" region="9 -10 11 -12" universe="1"/>
    <cell id="13" material="17" name="SP" region="-17" universe="2"/>
    <cell id="14" material="16" name="SP Water" region="17 9 -10 11 -12" universe="2"/>
    <cell id="15" material="15" name="Fuel Water" region="17 9 -10 11 -12" universe="3"/>
    <cell id="16" material="15" name="Fuel Water" region="17 9 -10 11 -12" universe="4"/>
    <cell id="17" material="13" name="Fuel" region="-15" universe="5"/>
    <cell id="18" material="5" name="Fuel Gap" region="15 -16" universe="5"/>
    <cell id="19" material="7" name="Fuel Clad" region="16 -17" universe="5"/>
    <cell id="20" material="13" name="Fuel" region="-15" universe="6"/>
    <cell id="21" material="5" name="Fuel Gap" region="15 -16" universe="6"/>
    <cell id="22" material="7" name="Fuel Clad" region="16 -17" universe="6"/>
    <cell id="23" material="7" name="Fuel Clad" region="16 -17" universe="7"/>
    <cell id="24" material="15" name="Fuel Water" region="17 9 -10 11 -12" universe="7"/>
    <cell id="25" material="6" name="Fuel Spring" region="-18" universe="8"/>
    <cell id="26" material="5" name="Fuel Spring Gap" region="18 -17" universe="8"/>
    <cell id="27" material="7" name="Fuel Clad" region="16 -17" universe="8"/>
    <cell id="28" material="15" name="Fuel Grid Water" region="17 5 -6 7 -8" universe="8"/>
    <cell id="29" material="6" name="Fuel Grid Inc" region="(-5 | 6 | -7 | 8) (9 -10 11 -12)" universe="8"/>
    <cell fill="1" id="30" region="13 -19" universe="9"/>
    <cell fill="2" id="31" region="19 -20" universe="9"/>
    <cell fill="3" id="32" region="20 -21" universe="9"/>
    <cell fill="4" id="33" region="21 -22" universe="9"/>
    <cell fill="5" id="34" region="22 -23" universe="9"/>
    <cell fill="4" id="35" region="23 -24" universe="9"/>
    <cell fill="6" id="36" region="24 -25" universe="9"/>
    <cell fill="4" id="37" region="25 -26" universe="9"/>
    <cell fill="6" id="38" region="26 -27" universe="9"/>
    <cell fill="4" id="39" region="27 -28" universe="9"/>
    <cell fill="6" id="40" region="28 -29" universe="9"/>
    <cell fill="4" id="41" region="29 -30" universe="9"/>
    <cell fill="6" id="42" region="30 -31" universe="9"/>
    <cell fill="4" id="43" region="31 -32" universe="9"/>
    <cell fill="6" id="44" region="32 -33" universe="9"/>
    <cell fill="4" id="45" region="33 -34" universe="9"/>
    <cell fill="6" id="46" region="34 -35" universe="9"/>
    <cell fill="4" id="47" region="35 -36" universe="9"/>
    <cell fill="7" id="48" region="36 -37" universe="9"/>
    <cell fill="8" id="49" region="37 -38" universe="9"/>
    <cell fill="7" id="50" region="38 -39" universe="9"/>
    <cell fill="3" id="51" region="39 -40" universe="9"/>
    <cell fill="1" id="52" region="40 -41" universe="9"/>
    <cell fill="2" id="53" region="41 -42" universe="9"/>
    <cell fill="1" id="54" region="42 -14" universe="9"/>
    <cell id="55" material="15" name="Guide Tube Inner Water" region="-43" universe="10"/>
    <cell id="56" material="7" name="Guided Tube Clad" region="43 -44" universe="10"/>
    <cell id="57" material="15" name="Guide Tube Water w Grid" region="44 1 -2 3 -4" universe="12"/>
    <cell id="58" material="15" name="Guide Tube Water w Grid" region="44 5 -6 7 -8" universe="11"/>
    <cell id="59" material="15" name="Guide Tube Water" region="44 9 -10 11 -12" universe="10"/>
    <cell id="60" material="15" name="Guide Tube Inner Water" region="-43" universe="11"/>
    <cell id="61" material="7" name="Guided Tube Clad" region="43 -44" universe="11"/>
    <cell id="62" material="6" name="Fuel Grid Inc" region="(-5 | 6 | -7 | 8) (9 -10 11 -12)" universe="11"/>
    <cell id="63" material="15" name="Guide Tube Inner Water" region="-43" universe="12"/>
    <cell id="64" material="7" name="Guided Tube Clad" region="43 -44" universe="12"/>
    <cell id="65" material="7" name="Fuel Grid Zr" region="(-1 | 2 | -3 | 4) (9 -10 11 -12)" universe="12"/>
    <cell id="66" material="15" name="Dash Pot Inner Water" region="-45" universe="13"/>
    <cell id="67" material="7" name="Dash Pot Clad" region="45 -46" universe="13"/>
    <cell id="68" material="15" name="Dash Pot Water w Grid" region="46 5 -6 7 -8" universe="14"/>
    <cell id="69" material="15" name="Dash Pot Water" region="46 9 -10 11 -12" universe="13"/>
    <cell id="70" material="15" name="Dash Pot Inner Water" region="-45" universe="14"/>
    <cell id="71" material="7" name="Dash Pot Clad" region="45 -46" universe="14"/>
    <cell id="72" material="6" name="Fuel Grid Inc" region="(-5 | 6 | -7 | 8) (9 -10 11 -12)" universe="14"/>
    <cell id="73" material="16" name="Support Plate Water" region="9 -10 11 -12" universe="15"/>
    <cell fill="1" id="74" region="13 -47" universe="16"/>
    <cell fill="15" id="75" region="47 -48" universe="16"/>
    <cell fill="13" id="76" region="48 -49" universe="16"/>
    <cell fill="14" id="77" region="49 -50" universe="16"/>
    <cell fill="11" id="78" region="50 -51" universe="16"/>
    <cell fill="10" id="79" region="51 -52" universe="16"/>
    <cell fill="12" id="80" region="52 -53" universe="16"/>
    <cell fill="10" id="81" region="53 -54" universe="16"/>
    <cell fill="12" id="82" region="54 -55" universe="16"/>
    <cell fill="10" id="83" region="55 -56" universe="16"/>
    <cell fill="12" id="84" region="56 -57" universe="16"/>
    <cell fill="10" id="85" region="57 -58" universe="16"/>
    <cell fill="12" id="86" region="58 -59" universe="16"/>
    <cell fill="10" id="87" region="59 -60" universe="16"/>
    <cell fill="12" id="88" region="60 -61" universe="16"/>
    <cell fill="10" id="89" region="61 -62" universe="16"/>
    <cell fill="12" id="90" region="62 -63" universe="16"/>
    <cell fill="10" id="91" region="63 -64" universe="16"/>
    <cell fill="11" id="92" region="64 -65" universe="16"/>
    <cell fill="10" id="93" region="65 -66" universe="16"/>
    <cell fill="15" id="94" region="66 -67" universe="16"/>
    <cell fill="1" id="95" region="67 -14" universe="16"/>
    <cell fill="22" id="136" region="89 -90 91 -92 13 -14" universe="23"/>
    <lattice id="22">
      <pitch>1.25984 1.25984</pitch>
      <dimension>3 3</dimension>
      <lower_left>-1.88976 -1.88976</lower_left>
      <universes>
9 9 9 
9 16 9 
9 9 9 </universes>
    </lattice>
    <surface coeffs="-0.61049" id="1" name="minimum x" type="x-plane"/>
    <surface coeffs="0.61049" id="2" name="maximum x" type="x-plane"/>
    <surface coeffs="-0.61049" id="3" name="minimum y" type="y-plane"/>
    <surface coeffs="0.61049" id="4" name="maximum y" type="y-plane"/>
    <surface coeffs="-0.61015" id="5" name="minimum x" type="x-plane"/>
    <surface coeffs="0.61015" id="6" name="maximum x" type="x-plane"/>
    <surface coeffs="-0.61015" id="7" name="minimum y" type="y-plane"/>
    <surface coeffs="0.61015" id="8" name="maximum y" type="y-plane"/>
    <surface coeffs="-0.62992" id="9" name="minimum x" type="x-plane"/>
    <surface coeffs="0.62992" id="10" name="maximum x" type="x-plane"/>
    <surface coeffs="-0.62992" id="11" name="minimum y" type="y-plane"/>
    <surface coeffs="0.62992" id="12" name="maximum y" type="y-plane"/>
    <surface boundary="vacuum" coeffs="0.0" id="13" type="z-plane"/>
    <surface boundary="vacuum" coeffs="460.0" id="14" type="z-plane"/>
    <surface coeffs="0.0 0.0 0.39218" id="15" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.40005" id="16" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.4572" id="17" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.06459" id="18" type="z-cylinder"/>
    <surface coeffs="20.0" id="19" type="z-plane"/>
    <surface coeffs="35.0" id="20" type="z-plane"/>
    <surface coeffs="36.748" id="21" type="z-plane"/>
    <surface coeffs="37.1621" id="22" type="z-plane"/>
    <surface coeffs="40.52" id="23" type="z-plane"/>
    <surface coeffs="98.025" id="24" type="z-plane"/>
    <surface coeffs="103.74" id="25" type="z-plane"/>
    <surface coeffs="150.222" id="26" type="z-plane"/>
    <surface coeffs="155.937" id="27" type="z-plane"/>
    <surface coeffs="202.419" id="28" type="z-plane"/>
    <surface coeffs="208.134" id="29" type="z-plane"/>
    <surface coeffs="254.616" id="30" type="z-plane"/>
    <surface coeffs="260.331" id="31" type="z-plane"/>
    <surface coeffs="306.813" id="32" type="z-plane"/>
    <surface coeffs="312.528" id="33" type="z-plane"/>
    <surface coeffs="359.01" id="34" type="z-plane"/>
    <surface coeffs="364.725" id="35" type="z-plane"/>
    <surface coeffs="402.508" id="36" type="z-plane"/>
    <surface coeffs="411.806" id="37" type="z-plane"/>
    <surface coeffs="415.164" id="38" type="z-plane"/>
    <surface coeffs="417.164" id="39" type="z-plane"/>
    <surface coeffs="419.704" id="40" type="z-plane"/>
    <surface coeffs="423.049" id="41" type="z-plane"/>
    <surface coeffs="431.876" id="42" type="z-plane"/>
    <surface coeffs="0.0 0.0 0.56134" id="43" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.60198" id="44" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.50419" id="45" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.5461" id="46" type="z-cylinder"/>
    <surface coeffs="20.0" id="47" type="z-plane"/>
    <surface coeffs="35.0" id="48" type="z-plane"/>
    <surface coeffs="37.1621" id="49" type="z-plane"/>
    <surface coeffs="39.958" id="50" type="z-plane"/>
    <surface coeffs="40.52" id="51" type="z-plane"/>
    <surface coeffs="98.025" id="52" type="z-plane"/>
    <surface coeffs="103.74" id="53" type="z-plane"/>
    <surface coeffs="150.222" id="54" type="z-plane"/>
    <surface coeffs="155.937" id="55" type="z-plane"/>
    <surface coeffs="202.419" id="56" type="z-plane"/>
    <surface coeffs="208.134" id="57" type="z-plane"/>
    <surface coeffs="254.616" id="58" type="z-plane"/>
    <surface coeffs="260.331" id="59" type="z-plane"/>
    <surface coeffs="306.813" id="60" type="z-plane"/>
    <surface coeffs="312.528" id="61" type="z-plane"/>
    <surface coeffs="359.01" id="62" type="z-plane"/>
    <surface coeffs="364.725" id="63" type="z-plane"/>
    <surface coeffs="411.806" id="64" type="z-plane"/>
    <surface coeffs="415.164" id="65" type="z-plane"/>
    <surface coeffs="423.049" id="66" type="z-plane"/>
    <surface coeffs="431.876" id="67" type="z-plane"/>
    <surface boundary="reflective" coeffs="-1.88976" id="89" name="minimum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="1.88976" id="90" name="maximum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="-1.88976" id="91" name="minimum y" type="y-plane"/>
    <surface boundary="reflective" coeffs="1.88976" id="92" name="maximum y" type="y-plane"/>
  </geometry>
  <settings>
    <run_mode>eigenvalue</run_mode>
    <particles>10000</particles>
    <batches>1000</batches>
    <inactive>50</inactive>
    <source particle="neutron" strength="1.0" type="independent">
      <space type="box">
        <parameters>-1.88976 -1.88976 0.0 1.88976 1.88976 460.0</parameters>
      </space>
    </source>
  </settings>
  </model>

[pshriwise]

Yeah I noticed this too, but haven't had time to dig into it. Thanks for creating an issue!

[nuclearkevin]

It looks like the error is getting thrown from openmc::PhongRay::on_intersection(). I'll see if I can figure out what's going on and patch it over the next few days.

[gridley]

Thanks Kevin! I would bet you this is a flaw in the plotter at large. It might be handy to isolate this as an XML input file to the plotter, then try reproducing it. I will also try to get to this at some point if you're not able to figure it out.

[pshriwise]

Perhaps we could modify the tool to write out the last plot config before the tool closes after this error to facilitate that.

[gridley]

That's an epic debugging option! If you all get that in and give me the XML, I could figure out the error in the plotter.

[pshriwise]

Placing this here for later, snagged an output by adding some registered call backs that are called in openmc::fatal_error before MPI_abort and std::exit.

Plot Type: Phong
Camera position: -69.99276733398438 -23.23891830444336 -3.0932064056396484
Look at: 0 0 0
Horizontal field of view: 45 degrees
Pixels: 400 400

[nuclearkevin]

@gridley this model.xml (with an accompanying plot) appears to cause issues with the ray traced plots. Notably, the saved image data has dimensions (0, 0) and the initial universe level is -1. It doesn't segfault when running OpenMC standalone, but it kills the renderer.

<?xml version='1.0' encoding='utf-8'?>
<model>
  <materials>
    <material id="1" name="Zirconium">
      <density units="g/cm3" value="6.5"/>
      <nuclide ao="0.5145" name="Zr90"/>
      <nuclide ao="0.1122" name="Zr91"/>
      <nuclide ao="0.1715" name="Zr92"/>
      <nuclide ao="0.1738" name="Zr94"/>
      <nuclide ao="0.028" name="Zr96"/>
    </material>
    <material depletable="true" id="2" name="UO2">
      <density units="g/cm3" value="11.0"/>
      <nuclide ao="0.0003166930253944235" name="U234"/>
      <nuclide ao="0.03543164439454172" name="U235"/>
      <nuclide ao="0.964089368630351" name="U238"/>
      <nuclide ao="0.00016229394971280895" name="U236"/>
      <nuclide ao="2.0" name="O16"/>
    </material>
    <material id="3">
      <density units="g/cm3" value="1.0"/>
      <nuclide ao="1.99968852" name="H1"/>
      <nuclide ao="0.00031148" name="H2"/>
      <nuclide ao="1.0" name="O16"/>
      <sab name="c_H_in_H2O"/>
    </material>
  </materials>
  <geometry>
    <cell id="1" material="2" region="-1" universe="1"/>
    <cell id="2" material="void" region="1 -2" universe="1"/>
    <cell id="3" material="1" region="2 -3" universe="1"/>
    <cell id="4" material="3" region="4 -5 6 -7 3" universe="1"/>
    <cell fill="2" id="5" region="9 -8 10 -11 12 -13" universe="3"/>
    <lattice id="2">
      <pitch>1.4427 1.4427</pitch>
      <dimension>2 2</dimension>
      <lower_left>-1.4427 -1.4427</lower_left>
      <universes>
1 1 
1 1 </universes>
    </lattice>
    <surface coeffs="0.0 0.0 0.46955" id="1" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.4791" id="2" type="z-cylinder"/>
    <surface coeffs="0.0 0.0 0.5464" id="3" type="z-cylinder"/>
    <surface coeffs="-0.72135" id="4" name="minimum x" type="x-plane"/>
    <surface coeffs="0.72135" id="5" name="maximum x" type="x-plane"/>
    <surface coeffs="-0.72135" id="6" name="minimum y" type="y-plane"/>
    <surface coeffs="0.72135" id="7" name="maximum y" type="y-plane"/>
    <surface boundary="vacuum" coeffs="150.0" id="8" type="z-plane"/>
    <surface boundary="vacuum" coeffs="-150.0" id="9" type="z-plane"/>
    <surface boundary="reflective" coeffs="-1.4427" id="10" name="minimum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="1.4427" id="11" name="maximum x" type="x-plane"/>
    <surface boundary="reflective" coeffs="-1.4427" id="12" name="minimum y" type="y-plane"/>
    <surface boundary="reflective" coeffs="1.4427" id="13" name="maximum y" type="y-plane"/>
  </geometry>
  <settings>
    <run_mode>eigenvalue</run_mode>
    <particles>1000</particles>
    <batches>110</batches>
    <inactive>10</inactive>
    <source particle="neutron" strength="1.0" type="independent">
      <space type="point">
        <parameters>0.0 0.0 0.0</parameters>
      </space>
    </source>
  </settings>
  <plots>
    <plot color_by="material" filename="test_plt" id="1" type="phong">
      <pixels>400 400</pixels>
      <camera_position>2.470304489135742 1.566969394683838 -27.163436889648438</camera_position>
      <look_at>0.0 0.0 0.0</look_at>
      <horizontal_field_of_view>45.0</horizontal_field_of_view>
      <diffuse_fraction>0.1</diffuse_fraction>
      <opaque_ids>1 3 2</opaque_ids>
    </plot>
  </plots>
</model>

[gridley]

Ah, I see. I would bet this relates to doing lattice corner crossings. It's documented in openmc-dev/openmc#2445. The fix would be to add checks if the corner is being crossed within epsilon in addition to each side of the current lattice cell, then advance to the relevant corner position.

Just a hunch! lattice crossings are this are one in a kajillion in particle transport, but commonplace in image rendering since it's very common to view the model from an angle in a way that's centered.