Cutting a triangular pyramid at precise z coordinates I'm trying to cut a triangular pyramid precisely into two pieces, a lower base part and the upper tip, as shown by the blue lines in the picture.



Vertices A B C must have the same exact z-coordinate.  So when the tip is cut away it will leave a perfecly flat (non-angular) surface.

I've tried subdividing and sliding vertices (Shift V) and trying to snap to a vertex in another mesh (with the required z coordinate), but its semms there is no vertex snapping for slide operations.

I also tried bevelling the top vertex to 0.0001 which allows using Edge loop and slide, but the same issue then occurs, ie no vertex snapping.

I could just add the vertex on each edge and then manually slide into place until I see the exact z coordinate, however I need to do this many times and it is relatively slow and error prone.

Is there a builtin way (or add-on) that simply lets us cut an object into two pieces precisely?
You can easily achieve this with a boolean modifier, using a plane.
Add a plane, set its height to be where you want to cut the pyramid,
then add a boolean modifier to your pyramid, set the plane as the object, and duplicate the pyramid.

One copy of the pyramid should have the boolean operation parameter set to difference (keep the top of the pyramid), while the other should be set to intersection (keep the bottom of the pyramid).

Apply the modifier on both copies to complete the process.