Code:
PolyVox::SimpleVolume <PolyVox::MaterialDensityPair44> volData (PolyVox::Region (PolyVox::Vector3DInt32(0,0,0), PolyVox::Vector3DInt32 (120, 120, 120)));
createSphereInVolume (volData, 60);
Results in the following:
Using a slightly smaller Sphere or increasing the Volume Size avoids the problem, probably because the Sphere reaches the bounds of the Volume? I have no idea.
If I use a Cubic Surface extractor, there are no issues with the vertices themselves though the cubes stop appearing at the edge like I expect it to.