Being able to easily live-edit geometry would open up a ton of possibilities when making games. To that end, I've built a simple toolset based around constructive solid geometry.
You can add and subtract brush shapes with arbitrary materials like this:
var world = new CsgSolid();
world.Add( CubeBrush,
DefaultMaterial,
position: Vector3.Up * 512f,
scale: new Vector3( 8192f, 8192f, 1024f ) );
world.Subtract( DodecahedronBrush,
position: Vector3.Up * 1024f,
scale: new Vector3( 1024f, 1024f, 512f ),
rotation: Rotation.FromYaw( 45f ) );
