topic Re: Terrain / Mesh - Contours with same X,Y but different Z in Modeling

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

Ancha — Wed, 29 Nov 2023 08:23:08 GMT

Hello,

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.

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

Nurbs — Tue, 28 Nov 2023 12:44:32 GMT

Hi,

Sorry that I have no solution beside of modelling two meshes (on on top of the other). But I have no problem with "cheating" by moving a point 1mm aside. At least this is a landscape and you will rarely find one with this accuracy in real.

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

Ancha — Tue, 28 Nov 2023 13:23:10 GMT

@Nurbs I agree that its not a problem to cheat. But you cannot keep track of all the points that you need to cheat in a bigger terrain. Its not your work to do this. The softwrae should provide you the solution.

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

david_skogvold — Thu, 30 Nov 2023 00:49:30 GMT

The mesh tool has the same limitations as topographical maps – they don't handle overlapping contours well. This unfortunately means that you can't create true verticals or overhangs using a mesh alone. While this is not ideal, overhanging or 100% vertical faces are very rare in nature, and in the few cases they are needed it should not be a huge task to work around. I find the mesh tool works OK for nearly all cases, even here in western Norway where a flat site is rarer than hen's teeth.

The quickest way would be as you suggest offsetting the upper contour a small distance. If you still need to model a true vertical or overhanging feature, you could create the main part of the terrain using a mesh, and then adding the missing geometry using a morph, wall or other object that fits the geometry you want. Match the building material and surface, and it should blend nicely in 3D, section and elevations. Site plans might need a bit of extra linework to get it to show exactly the way you want (dashed lines for contours beneath overhangs). This should also be relatively easy to edit, since most of the terrain is kept as a mesh and only the "odd" part is modeled separately.

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

Ancha — Tue, 28 Nov 2023 13:54:18 GMT

These are good workarrounds if you want to "design" the terrain.
The problem here is that when you create a terrain that you wanna keep as guide for the exhisting terrain all along the project, you cannot keep track of all the places where the terrain is created correctly by the programme, or track where one of the hunderds of the contours is overlapping with some other (is there a quick way to do this btw?). Imagine a big project, starting from concept design, but later you need the exact terrain details. Do you then need to consult the initial topo-files that you got? To doublecheck that the places where you gonna do the design where correctly made by ac?
The issue is that you do have a mesh but it is not correct.
The software now can create only the A option:

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

david_skogvold — Tue, 28 Nov 2023 14:39:44 GMT

True, only option A can be done using a mesh. I agree this is not ideal, and would also like a more advanced mesh tool, but I think you may be trying to make a simple tool (terrain mesh) do something it's not meant for.

It would be easier to suggest a workflow if you showed an example of the data you want to import, I am thinking you could use the morph tool as a kind of advanced mesh and keep much of the editability, but the initial generation of it may involve a bit more manual work than just importing your 3D contours and automatically generating a mesh from them.

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

Ancha — Tue, 28 Nov 2023 15:51:41 GMT

Yes it is going to be crazy manual work. Too much work if you think you already have the inforamtion in dwg file (2D contours elevated in correct Z).
You cannot efficiently work with morphs for terrain. The morph tool does not give you the option to elevate the whole polyline, you can just select one by one the edges (unrealistic in real terrain).

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

david_skogvold — Tue, 28 Nov 2023 16:46:22 GMT

Maybe, but not necessarily. Still struggling to see exactly what you are trying to do, so some sample data of what you're working with as input would be helpful.

You can in fact select and elevate a whole contour line on a morph - try making a simple mesh with a few contour lines, make sure to set it to "show user defined ridges" and "user ridges sharp". Now convert this mesh to a morph, and it will work. The key to this seems to be - only the contour lines are sharp/shown, the other lines describing the triangulation are hidden/softened.

If you need a single, editable terrain with verticals and/or overhangs, I would try something like this. First create the mesh (minus overlapping parts), then convert to morph, and finally move the contour lines that need to overlap into their correct shape.

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

Ancha — Fri, 01 Dec 2023 07:39:04 GMT

I need to model a 300.000 m2 area that has this king of terrain. It is not about what I need to do, but how to do it.

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

Barry Kelly — Fri, 01 Dec 2023 08:00:36 GMT

What is creating those vertical contours in your terrain?

I have never seen a natural site with exactly vertical contours.

Myself, I would place a wall there.

With the lower site contour on the outside of the wall, and the upper site contour inside of the wall.

The thinner the wall the closer the contours will be - but at least you will have a perfectly vertical surface.

It is simply impossible for a mesh in Archicad to have contours vertically above each other, or where the upper contour cantilevers out over the lower contour.

So you will need to use morphs or walls or other elements to get that effect.

Or use Solid Element Operations to cut the vertical surfaces.

No matter what method you use, you can not have overlapping contours.

Barry.

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

Ancha — Fri, 01 Dec 2023 08:03:07 GMT

(this is in Norway btw)

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

martin-b — Fri, 01 Dec 2023 13:27:25 GMT

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.

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

Ancha — Fri, 01 Dec 2023 13:36:22 GMT

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).

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

Jim Allen — Fri, 01 Dec 2023 17:33:35 GMT

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!

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.

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

Barry Kelly — Sun, 03 Dec 2023 07:46:13 GMT

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.

Barry.

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

Ancha — Mon, 04 Dec 2023 10:48:33 GMT

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

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

Ancha — Mon, 04 Dec 2023 11:05:48 GMT

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.

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

Jim Allen — Mon, 04 Dec 2023 11:07:53 GMT

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.

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

Ancha — Mon, 04 Dec 2023 11:11:40 GMT

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.

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

david_skogvold — Mon, 04 Dec 2023 15:17:32 GMT

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.