User's Guide ‐ 3‐Point Clipping Tool
Source Level Editor 2.104
SLE also updates the regular verson in a couple ways; more on that at the bottom.
The new clipper also works by setting up points in a viewport, adjusting if necessary, and confirming clipping by pressing Enter (or opening the context menu with the right mouse button).
The difference is it has 3 plane points, each coloured to help differentiate them, especially when working in both 3D and 2D viewports.
At first, one of the points is always "hidden" under another in 2D, because they will be placed at first along the "depth" axis of that viewport. However they can be dragged from "under" another handle, after which it is easy to move all 3 coloured handles in the viewports.
Only 2 out of 3 handles are visible...
The third one simply needs to be dragged from "under" another. Regular Clipping Tool updates
The regular clipper now reports the clipping plane relative angle. The perceived horizontal (of the viewport) is 0 degrees, and vertical is 90; all angles are shown within this span, as in, moving the plane so it faces the "opposite" does not make it report the angle as a negative or going over 90.
A vertical plane counts as 90 degrees.
Both these planes count as ~30 degrees.
The clipping plane handles can now be placed and moved in the 3D viewport.
In the case of the 3-Point Clipper, this is arguably its main mode as it means simply clicking three times to form a plane, then confirming the operation - very straightforward.
With the regular clipper, it may be a little more odd at first, as the clipping plane may be placed counterintuitively or it may require placing and moving the handles before it is visible.
Moving the handles works the same way as moving selected objects or vertices in the Vertex Edit - just drag them with the left mouse button.