Volumetric flood fill

[kephale]

Can we do this in a volume? https://forum.image.sc/t/converting-stl-file-into-stack-of-images/1721/79

Could generate a test case by taking https://github.com/scenerygraphics/sciview/blob/master/src/main/resources/WieseRobert_simplified_Cip1.stl, using Voxelization, flood fill at a target location, sum the number of pixels to do the test. Be careful about the dimensions of the voxelization to ensure a watertight boundary (maybe use a dilation afterward to be sure).