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About Archicad's design tools, element connections, modeling concepts, etc.

Terrain / Mesh - Contours with same X,Y but different Z



After personal research without finding a good enough solution I come here asking:

How to model a terrain that has some contours overlapping (meaning they have same x,y but different z = the terrain has a vertical cut)??

Example diagram here:


...If this is modeled the "correct way" = creating mesh > creating the contours on the mesh > elevating each contour to the correct Z, then the outcome will be this one:



The problem is that the points that belong to the both contours cannot be the one above the other, they are merged...

And the solution cannot be to "cheat" the modeling by moving the one contour 1mm so they are not overlapping. Nor can be to create morph to adjust it manually.

And this beacause the terrain-modeling is the beggining of the design and really should be an automated process like in other programs - you import the contours in 2D and in correct elevation and the mesh is automatically generated. You cannot just scan each milimeter of your generated mesh if there are parts that overlap and be unsure if the quality of the mesh is not correct in 3D or in the sections.
How people deal with this? Am I the only one that uses archicad in projects that are not just 1 plane mesh with maybe 3-4 contours..

Any ideas are welcome.

Thank you in advance.




(this is in Norway btw)


Archicad is not really an ideal tool for modelling such terrain that you have in mind. It can handle basic models, but it has its limitations. It it not primairly a tool for modelling large landscapes.


Like the others said, it is not possible to model terrain with faces that go straight down or even under itself within the same Mesh object.


Didn't you consider using some other tool than Archicad if you already have your contour lines in the right height in DWG?

Just generate you terrain in Grasshopper for example and then you could import your geometry as a Morph when it's done.

Apparently this is the only way to do it, if you dont want to spend a century on modeling every place with morph. I will try the Rhino - Archicad - Grasshopper Toolset. I doubt that the outcome is precise enough though (and definatelly not adjustable in bim).

The mesh tool is very old and pretty inflexible in this regard, your only option is the A solution you have drawn. I get this all the time when I get terrain models with retaining walls.


In fact the whole process of modelling complex terrain on large sites is poor. Importing meshes from surveyors's data gives randomised (non-weighted) triangulation. Terrain maps from surveying software have weighted geometry. This means that points identified top of wall or top of kerb or top of bank are all connected, so the triangulation is pretty representative of the actual terrain.


Except you can't import these types of terrain models, because they are typically in dwg form, and they can't be imported as meshes.


I have been told that the options are to use something like Rhino and import into Archicad, or use something like Land 4.


It's not clever, and I almost never have flat sites in my part of the world. I don't think the 'solution' of drawing walls onto your terrain map is a good one because existing walls will be different heights, widths, and the tops won't be horizontal. It's fine if you are going to replace them, but if not it's awful and time-consuming. I've done this for the model in the attached image below and it took days!



Screenshot 2023-05-19 at 13.49.34.png

That was in addition to modelling the actual terrain itself which took even longer.

The only solution is to redraw the contours, adjust where necessary to avoid coincident Z points and model the terrain manually by elevating contours and intersecting them.


Vectorworks does a much better job with this. You define a shape, select some 3d polylines, define the height intervals and it creates the terrain automatically. It's kind of like the Archicad process, but automated and much easier!


As David has said, you can convert your mesh to a morph, but you lose all the benefits a mesh gives you, and you may as well not have the tool at all.


Terrain modelling with the mesh tool is one of my biggest gripes with Archicad.


This tool is too simplistic, and the import options for meshes are way too limited and crude.

Archicad 27 UKI | OS X 12.7.1 Monterey
Barry Kelly

I had a little think about this.

Why not just use 2 meshes.

The edges (or skirt) of the mesh is always vertical.


Create the main mesh with the contours and set their heights.

On the contour where you want the vertical face, cut a hole.

On the edges of that hole on the faces you want to be vertical, ensure the node heights are at the lower contour level.


Now add a new mesh and elevate the perimeter heights to the upper contour level.

Add more contours on top of this if you need.


Repeat if you happen to have more vertical surfaces.





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This is not working btw, you cannot select the whole polyline..



Thank you Barry, this is actually a good workarround for the vertical sqenario and can easily be applied if the issue is just in 1-2 known places of the site. 
And this, without any imports from other software or morph tools.
Basically, this could be the answer for this question, although the main purpose of the question was to do this more automatically - like the standard terrain modeling process, for bigger sites whitout having to figure out where the terrain is vertical.

This is a really neat solution, but it's not really the 'right' answer, because what we want is to just import proper terrain geometry as a mesh and be able to use the mesh tools to modify it.


That's not possible currently. I might try Land4 and see if that will work.

Archicad 27 UKI | OS X 12.7.1 Monterey

Agree. Just markin it as solution because it answers the "diagram" problem (I believe the majority of people will have this issue - not the big terrain issue). The real problem should be escalated to the wish list I guess or in a more specific question.


You are right, I tested it again and it seems like AC only merges the whole edge if the angle between straight segments are below a certain threshold – it seems like sharper corners will result in split edges when converting the mesh to a morph.


FWIW, this can be corrected:

1) Make sure hidden morph geometry is OFF

2) Use find & select or manually select all the visible edges

3) Change their edge type to hidden / smooth, and then back to hard again (luckily, AC keeps the edges selected after hiding or smoothing them)


This should unify all the contour lines as intended. For editing individual vertices after this, hidden morph geometry must be turned back on.


This might still be too much manual work for your current project, but it might be useful for other cases where one wants to add a bit more flexibility to a terrain mesh while keeping some degree of editability.


See attached video.

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