Modeling a terrain as a solid (not a mesh) in Autocad, with a smooth surface

[teocruz105]

Hi. I've been facing problem creating a solid 3D terrain in AutoCad. I'm using DRAPE to create a mesh from curve level. the Mesh looks great. But I need it as a solid. So when I convert it to a solid, the surface looks really bad. I need it as a solid to edit it as such, and the then to export it to STL. The stl file will look as bad as the solid. Does any one know a procedure which allows me to creat a decent solid terrain in AutoCad as solid? I posted this question here some weeks ago( https://forums.autodesk.com/t5/autocad-forum/modeling-a-terrain-solid-not-a-mesh-with-a-soft-surface...

and I received good adviceces, but the issue is not solved yet. I am attaching a file that can better explain what I'm talking about.

[j.palmeL29YX · Accepted solution]

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@teocruz105 wrote:

 I'm using DRAPE to create a mesh from curve level. the Mesh looks great.

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Some notes:

1)

The mesh LOOKS (perhaps) good, but its surface is far away from the level curves (as shown in >>this video<<. (and a lot of others).  Is this accuracy really good enough for you or for your further purposes?

2)

I doubt the correctness of the level curves. In the video I show where two curves at different Z-leves cross each other. That never can be correct.

3)

I don't know DRAPE, but obviously it creates a triangulated mesh as result. I don't know a way to convert it into a smoothed solid automatically.

Did you try what I suggested in the other thread? What doesn't work for you (" the issue is not solved yet.")? I know it is a lot of manually work. But if you want it to do more comfortable, the plain AutoCAD seems to be the wrong software.

[teocruz105]

Hi

Yes, I tryed your suggestions. However, since I have to slice the part that I have made with the same wronw method, the lines extracted from that solid will lead to a solid with the same impefections. For example, in the sample you provided, the faces are still there. I am using drape, a command from autocad architecture, and them I bring the solid back to autocad plain. With regards to the crossed lines, that is just a sample. But lines with different  height does cross when they describe a  part of an elevation that is wider on the top than it is in the bottom. I do think you might be right...It looks like AutoCad Plain is not the most appropriate softwere for this specific work.

[j.palmeL29YX · Accepted solution]

The attached dwg shows the result after "smoothing" the (example) solid which you posted above. I used the method which was suggested in my older post. The upper face is a smoothed NURBS surface without triangular faces. (You find the surface at the layer "New_surface").

>>the lines extracted from that solid will lead to a solid with the same impefections<<

Did you

...

* join the lines of the upper contoure to a polyline
* Smooth the polyline (pedit -> spline)

... ?

If you now create a lofted surface using this smooth polylines you get a smooth surface.

But I am with you: >>AutoCad Plain is not the most appropriate softwere for this specific work<<

[leeminardi · Accepted solution]

The fact that you plan to export the final model  as an STL file somewhat negates the need for a smooth surface as an STL file will have  tessellated any smooth surfaces.

As an experiment I imported the AutoCAD solid model into 3ds Max and applied a turbosmooth modifier.  Here's how it looks in Max.

 

And then converted it to a .dwg file in Max.  Here's how it looks back in AutoCAD.  It's a mesh surface which would require using surfsculp to convert it to a solid.

[R_Tweed · Accepted solution]

Q. Did they add drape to Autocad ? I thought that was an ACA only command.

The steps below would give you a smoother solid than drape to mass to solid. I would recommend you start with drape as a tool to generate the profiles needed for a surface network.  There might be ways to speed the process along but this will give you an outline. I've attached a sample file and stl file.

1. Use drape if available. If not. you can trim, break contours along a grid and draw profile splines

2. Cut sections at reasonable spacing and leave in place

3. Isolate each profile and retrace the top (surface) with spline.

4. Repeat steps for other direction.

5. Network a surface from the splines

6. Make a solid as a cube of the extent.

7. Use slice and the surface to trim the solid.

[R_Tweed]

I didn't catch that you were using aca., I should've read the posts more closely.  The profiles for the network surface can be made from the mass model using split by plane, isolate by elevation and then using a boundary command you can make your base profile.  Once you have the base profile you can make a spline by using the cvrebuild command. See <screencast> 

[teocruz105]

Thank you,  avengineering, leeminardi and J Palme for your suggestions. I will try each one of your advices and come back to you. All these solution sounds really promising.

[teocruz105]

Thank you, J Palme.

I see that by following your directions I can get exactly what I am looking for.

[teocruz105]

Thank you, J Palme.

I see that by following your directions I can get exactly what I am looking for

[j.palmeL29YX · Accepted solution]

As reply to your (PM)request:

In >>this video<< you can see in detailed steps what I did.

HTH

[teocruz105]

J Palme,

Thanks to your instructions I just have done my first 3D solid terrain, with a smooth surface. 

[teocruz105]

The smooth surface

[j.palmeL29YX]

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@teocruz105 wrote:

The smooth surface

>>The surface looks very well. The only thing is that it won't thicken.<<

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Thicken works well, but only with small values. With higher values you will get a self overlapping volume, this is not allowed and not possible in AutoCAD.

>>Here<< my suggestion to get a solid with a smoothed upper surface.

If my reply solves your problem, click the "accept as solution" button. This can help others find solutions faster

[Anonymous]

hi i have a  similar problem with my model as well. I want to convert traingualted polymesh terrain to solid in autocad as it is disregarded in CFD simulation tool simcentre star ccm+. Can you please suggest me steps to convert terrain to solid of the following model.

[j.palmeL29YX]

Is this what you are looking for? 

(Be aware: the terrain are two solids - one around the buildings and a second underneath the buildings). 

I converted the buildings into a solid too. If you don't need that, you can use your block instead. 

[Anonymous]

Thanks .it seems like it works but can you please reduce the thickness of the terrain to minimum.

[j.palmeL29YX]

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@Anonymous wrote:

 reduce the thickness of the terrain to minimum.

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What do you mean? Which "minimum"? Do you mean a terrain with a constant thickness (similar as the result of an offset)? If yes, which value do you need or wish for the thickness?  

Or do you need the "box" with a smaller height. This can you do yourself: create a plane at the wished z-value, the yx-dimension greater than the terrain and slice the volume which you don't need. 

Attached an improved version where the complete terrain is ONE solid. 

[Anonymous]

Hi, terrain thickness level is not a precise value for my case but in order to reduce the size of file when exported to iges format i was interested to have minimum thickness. can you please reduce it to the marked level as in the pic i have sent you. then i think i will be able to work in simcentre star ccm+. Thank you so much for helping out. I am using it for my thesis.

[j.palmeL29YX]

If you want or need you can do >>this<< of course on another Z-value. Move the Planesurf along the Z-axis where you want. 

(BTW: To reduce the height of the terrain box will not reduce the file size significantly) 

Please mark "Accept as Solution" if my reply resolves the issue or answers your question, to help others in the community.