[derekm]

ViewFactorsGen will crash if you use baffles in interesting ways. This is because
ViewfactorsGen does not handle patches which are coincident e.g. baffles
the following function in //OpenFOAM-2.3.1/applications/utilities/preProcessing/viewFactorsGen/viewFactorsGen.c attempts to divide by the scalar distance rmag between the two patches ( i j) as shown below. If the patches are coincident ~ BOOM

scalar calculateViewFactorFij
(
    const vector& i,
    const vector& j,
    const vector& dAi,
    const vector& dAj
)
{
    vector r = i - j;
    scalar rMag = mag(r);
    scalar dAiMag = mag(dAi);
    scalar dAjMag = mag(dAj);

    vector ni = dAi/dAiMag;
    vector nj = dAj/dAjMag;
    scalar cosThetaJ = mag(nj & r)/rMag;
    scalar cosThetaI = mag(ni & r)/rMag;

    return
    (
        (cosThetaI*cosThetaJ*dAjMag*dAiMag)
       /(sqr(rMag)*constant::mathematical::pi)
    );
}

FIX: This can be fixed by substituting the following

scalar calculateViewFactorFij
(
    const vector& i,
    const vector& j,
    const vector& dAi,
    const vector& dAj
)
{
    vector r = i - j;
    scalar rMag = mag(r);
   
    scalar dAiMag = mag(dAi);
    scalar dAjMag = mag(dAj);
    if ( mag(r)==0)
    { return 0; } 
    else
    {
    vector ni = dAi/dAiMag;
    vector nj = dAj/dAjMag;
    scalar cosThetaJ = mag(nj & r)/rMag;
    scalar cosThetaI = mag(ni & r)/rMag;

    return
    (
        (cosThetaI*cosThetaJ*dAjMag*dAiMag)
       /(sqr(rMag)*constant::mathematical::pi)
    );
  }
}