Take a look at this screenshot
Can LISP extract the footprint, for example the top-face and bottom-face of these volumes, which could be meshes or solids?
I have a solution how it can be done in 3dsMax, but I am investigating this to be done directly in AutoCAD environment.
If they're always and only simple shapes with vertical side planes as in your image, you can draw another rectangle or Circle or any closed shape that completely surrounds them, and use BOUNDARY, picking a point inside that surrounding shape but outside any of the objects. Eliminate the surrounding shape and the resulting Polyline or Region that coincides with it, and the remaining resulting Polylines or Regions will be the footprints of the objects [though only one per object, not top and bottom planes].
If the objects have "simple" complications, like taper but with top and bottom planes parallel to the drawing plane [such as from a simple EXTRUDE with a taper angle], Boundary makes results that duplicate the shapes of both the top and bottom surfaces, though both at Elevation = 0. I haven't experimented with what happens when they have further complications such as sloped top surfaces, more complex notches cut out, holes through them, etc. -- I leave that to you if you have those kinds of configurations to deal with.
@Haider_of_Sweden wrote:
.... The extracted footprints need to have the same elevation as the surfaces they were extracted from.
And what exactly do you mean by "extracted"? If you just want to have them in the drawing as separate drawn objects from the source objects, can you simply EXPLODE each source object [or a copy of it]? You'll get Regions for all the faces from a Solid, or 3DFaces from a Mesh, and they'll be at the right elevations, orientations, etc. If you mean you want only certain ones among those, as Message 1 implies, then some coordinate evaluation as already suggested by @marko_ribar would help identify the right ones, depending on the complexity of the shapes. If, on the other hand, "extract" involves something else, such as putting information about them into an external file, that's another level....
Please take a look at the screenshot, a scene could look like this:
I also provided some sample DWGs:
Buildings Footprint 3D solids.DWG - buildings in 3D. They all have the same height. In a real model, the buildings would most likely have different heights.
Buildings Footprint 3D mesh.DWG - as stated before, my question was also about mesh-objects, whether a LISP could handle mesh surfaces and not only solids.
Buildings Footprint 2D top level - this one was made in 3dsMax. The footprints are generated based on the top-faces of the volumes. THIS is the result I am looking for, but in AutoCAD. Why? Because I want options. I don't want to be dependent on 3dsMax.
Both the BOUNDARY and XEDGES commands were cool and useful (no matter how good I think I am in AutoCAD, there are still commands I didn't know of 😄 ). So thanks for those tips, but still, they are not relevant in this case.
@Kent1Cooper - with "extract" I mean have.
The project could be much larger than the sample file, therefore exploding and manually doing this will simply not work. This is why I hope this thread will result in a scripted/automated solution.
@Haider_of_Sweden wrote:.... This LISP need to be able to create polylines that represent the exact same face locations as the original solids .....
I was thinking one could Explode a Solid into Regions, Explode the Regions into Lines, Join the Lines into Polylines, assuming they would be rectangles, and then compare the coordinates of their corners to decide whether they lie in a horizontal or a vertical plane. If a rectangle has two corners at one Z coordinate value and the other two at another, it's one that came from the side of a Solid, and could be eliminated.
But I find that the boxy Solids Explode into Regions that all seem to be triangles, and the Solids' faces are made of multiple triangles, not rectangles:
I guess there could still be some analysis of which of them should be eliminated and which kept, but I'm not sure it would be possible to come up with [for example] the rectangle that represents the top of that box.
