union3d
The boolean operator <union3d> specifies the union of a set of solids contained. The result is a new solid.
Example with the 3d union of a sphere and a centered cube.
<?xml version="1.0" encoding="utf-8"?>
<xcsg version="1.0">
<union3d>
<cube size="50" center="true"/>
<sphere r="33"/>
</union3d>
</xcsg>