A quick shadow-casting cage

  1. Create geometries with the necessary frame. The Follow Me tool works well for this. Make hidden geometries visible (View → Hidden Geometry)
  2. Select the geometries and unsoften/unsmooth them (Window → Soften Edges). Erase edges you do not want.
  3. Activate the Wireframe face style. (View → Face Style → Wireframe) Make sure nothing is selected, then select only the edges with ctrl+a or command+a. DO NOT do a rapid-select by triple-clicking as that will also select the faces.
  4. With just the edges selected, copy them with ctrl+c or command+c.
  5. Activate a face style that displays faces, select and delete everything. (Your edges are still on the clipboard from the previous step)
  6. Edit → Paste in Place. Turn on shadows from Window → Shadows, and check the From Edges option.