hull3d
The boolean operator <hull3d> specifies the 3d hull of a set of solids contained. The result is a new solid.
Example with the 3d hull of an offset sphere and a centered cube.
<?xml version="1.0" encoding="utf-8"?>
<xcsg version="1.0">
<hull3d>
<cube size="50" center="true"/>
<sphere r="33">
<tmatrix>
<trow c0="1" c1="0" c2="0" c3="25"/>
<trow c0="0" c1="1" c2="0" c3="25"/>
<trow c0="0" c1="0" c2="1" c3="0"/>
<trow c0="0" c1="0" c2="0" c3="1"/>
</tmatrix>
</sphere>
</hull3d>
</xcsg>