Cutting one object with another (and not deleting a mesh)

I’m trying to cut through a mesh using another. The catch is, I need both meshes to stay intact. I believe this means I can’t use the Boolean modifier as as far as I know, it deletes one mesh.

I’ve attached a picture. The selected vertices are the object to be cut-through. The horizontal plane is the object to do the cutting.

(I can’t use a knife tool easily, as I need the cuts to align perfectly with the bumpy surface of the horizontal plane)

I thought the Knife Project tool would work. In object mode I selected the horizontal plane, Right click and shift selected the object to be cut. Then in Edit Mode I selected Knife Project. The results however were this:

Any ideas would be really helpful right now. Thanks.

Join the objects. Intersect (knife) in edit mode. They’re in faces menu, ctrl+F.

Here is my experiment where I shaped one object with another.

I used Dynamic Paint displace functionality.

Thanks JA12. I can’t join the objects as one is an item of clothing on an armature. When I select both meshes and try and join them, the mesh on the armature defaults to Rest Pose and no longer intersects with the horizontal plane.

Also, thanks nilsauta for the video. I’m not sure it’s the same functionality I’m looking for but it’s a really great experiment.