Solid element operations on a target using only one skin in a multi-skin composite operator

[Paul King]

Has anyone come up with a clever way to perform solid element upwards subtract extrusion operations on a target using only one skin in a multi-skin composite operator.

Materials in the composite operator element that I don't want to cut the target are set with lower materials priority than the target element material, and the material that I do want to act as a cutter has higher materials priority  - however when I attempt to use the operator on the target to do an upwards subtraction, the low priority material nevertheless cuts the target anyway.

No doubt I am missing something obvious here, but can anyone assist?

Crude markup below

This is a composite roof consisting of a plywood skin on an insulation skin, where I want only the plywood part to cut the rafters with upwards extrusion.

The red dots indicate extent of desired cutting of the rafters, and the green dots indicate the base of the rafters that should be left uncut by the operator element.

What actually happens is that the base of the cut is from the base of the insulation, even though materials priority of insulation is lower than for the rafters it is cutting.

[Eduardo Rolon]

Strong Air BMat for the win…

[Erwin Edel]

Not sure if it's been suggested, but you can use a segmented beam, which you can either save as a favourite or use the syringe to transfer element settings to other beams.

Either set (or change) the reference axis to bottom, or make a complexprofile that you can stretch from the top or just give it the fixed size needed.

If you give the notch and the start of the beam a fixed size and set the rest to '100%', you should have a stretchy solution.

Similar issue and the solution:

[Eduardo Rolon]

That was my initial recommendation that I deleted (and shouldn't have) reason that it does not work is that it needs to be manually updated if the roff pitch changes, if I understood correctly.

[Paul King]

Yes, that was the problem.  Far too many beams being notched by roofs to do each one manually, for each iteration of roof fall geometry and beam depth being considered.

[Erwin Edel]

If the notch is the same, the total lenght can be different. You can just select all your existing beams and add the notch, as long as some part of the beam has no defined length. Or you can use the Adjust function etc afterwards to connect your beams as you normally would.

That's what I tried to show with the screenshot. My notch there is 30 mm, the rest is 100%. The beam can be any lenght (greater than 30 mm obviously), but the notch will stay the same. You can stretch it as any other beam, it just has a fixed size part.