geom:volume

(geom:volume solid)

The solid's volume, by the divergence theorem over its mesh triangles. It doubles as a winding check: a facet wound the wrong way SUBTRACTS, so a mis-wound solid answers a grossly wrong number rather than a slightly small one. A tessellated primitive is inscribed in its smooth ideal, so its volume converges on the closed form from below. See the solid modeling guide.