static Box3d Transform2(Box3d box, M44d trafo)
{
var xa = trafo.C0.XYZ * box.Min.X;
var xb = trafo.C0.XYZ * box.Max.X;
var ya = trafo.C1.XYZ * box.Min.Y;
var yb = trafo.C1.XYZ * box.Max.Y;
var za = trafo.C2.XYZ * box.Min.Z;
var zb = trafo.C2.XYZ * box.Max.Z;
return(new Box3d(
V3d.Min(xa, xb) + V3d.Min(ya, yb) + V3d.Min(za, zb) + trafo.C3.XYZ,
V3d.Max(xa, xb) + V3d.Max(ya, yb) + V3d.Max(za, zb) + trafo.C3.XYZ));
}