You can trim a part of an existing 3D freeform space by trimming one of its surfaces.
Note: This procedure is valid for non-associative spaces only. If you perform it on an associative space, it will loose associativity after exiting the in-place edit mode.
Trimming a 3D space
Verify that you are working in a 3D isometric view.
Select the space you want to trim along the horizontal or vertical plane.
3D space (left) in in-place editing mode (right)
Click Space tabModify panelEdit In Place.
Click Edit In Place tabModify panelTrim By Plane.
Specify the trim plane either on screen or by entering 3 points on the command line.
Tip: Use a Front view to generate a horizontal trim plane and a Plan view to generate a vertical trim plane.
To save the changes to the space, click Edit in Place tabEdits panelFinish.