This sort of stuff is usually done in a dedicated CAD processor like AutoCAD.
If your plane is parallel to any of the global coordinate planes, you can use the "Edit -> Divide... -> by a plane" option in Robot's menu, specifying the correct coordinate and plane type.
It is possible to write small COM macro (in VB or C) doing that. Even, if you create dll for it , it is possible to add it to pull down menu by Add-ins Manager.
I am attaching screen shot of the option doing exactly what you want made by one of polish users.
I find your add-in very useful too. Can you make it public?. Consider that the reported problem is very common because rhe analitical model often come from REVIT that, as you probably know, has problems with analytical models of complex tilted slabs.
Memo: analytical model is something that has a closed form solution. The models that we have are called numerical or FE.
I perferctly understand your argument here, knowing that Autodesk has been promoting this term for quite a long time.
Yet to understand each other, I tend to think we should use terminology defined by science and the engineering community, not a vendor whose software some of us engineers happen to use.
Hi, I have used the object combination and used cutting off along an arbitrary plane after drawing a wall in the plane of the column. Then I trimmed the column with the edge of the wall and it works just fine. No need for a macro. Hope this helps.
Structural Design Engineer
MZ & Partners Engineering Consultancy