Terrain modelling

[eirik.kjolsrud]

Dear all.

After an executive decision to utilise our ACA 2010 for 3D models and not only for 2D drafting we are struggling with the 3D modeling in the office..

We find it especially hard to make a proper site model for our latest project. We have been searching the internet for solutions, but mostly they just say: "in Autocad it is too difficult, go ahead and buy Civil3D". That is unfortunately not an option for us, we have to get by using the built in functionality of ACA 2010.

So far, I have come across some references to LOFT and DRAPE. As far as I understand, these will create solids that are system intensive and hard to edit, but I might be wrong? There was also a mention of the new mesh capabilities of AutoCAD 2010, and EDGESURF, but we have been unable to make it work.

Very quickly explained, our site is a hill with a road on the bottom and at the top. We have elevated polylines that represent the contours. We would like to model the site with roads and sidewalks, and we would like the road, sidewalk and hill to have different textures.

How would you go about modeling this site? What are your methods?

Any help would be greatly appreciated.

[eirik.kjolsrud]

just a quick update on my progress...

I have tried to use EDGESURF to create mesh objects for the site, and EXTRUDE for the roads and sidewalks.

When I use the EDGESURF command and select the two contour lines plus their edges (endpoint of contour lines connected with 3DPOLY) I get a mesh, but as this mesh doesn't strictly adhere to the contour lines, I get a problem when I move on to the next set of contours. The meshes overlap and sometimes there will also be a small gap. Is there a way of forcing EDGESURF to stay within the lines?

The problem with EDGESURF is that it requires 4 edges as an input, because then I have to create a mesh for each set of contour lines and because of the problem mentioned above, my site is full of small holes.

Is there a better way of using EDGESURF, or is it better to use another command altogether?

Cheers, eirik

[eirik.kjolsrud]

I've attached an image illustrating the gaps mentioned in the above post.

Also, on the textures, I have only put the various mesh objects in layers with a colour conceptually representing the material, but I am sure there is another way of adding textures to the site?

[eirik.kjolsrud]

I've managed to build a nicer model using the LOFT command.

I had the same problem here though, if I selected all the contour lines the mesh does not at all resemble the site, it gets all twisted with extravagant curves here and there. If I LOFT one section at a time, the site looks ok. This might be harder to edit later?

I've attached an image showing the difference between the EDGESURF and LOFT terrain. The LOFT version is much more complicated and probably then harder to edit and is harder on performance?

...

Is there a way to create the mesh terrain as one single object and not as separate slices as now? Or is it ok to keep it like that? Should I group them? ... I'm very interested to hear about your methods.

Cheers,

Eirik

[david_peterson]

Eiric,
Use the Drape tool. It creates what I believe is a mass element hybrid. ACA objects are NOT solids. They are different. Depending on how smooth you want the surface will determine how much memory it will eat up. Also don't forget that once you switch from a shaded display to a 2d line work display, less memory is used. You can also simply hide the object if you don't want to look at it while you work.
Paul's Book goes into some good detail on site plans and best practices.

[eirik.kjolsrud]

Thanks David.

I tried with drape, but it didn't really work. I couldn't get an accurate result, because it did not recognize contour lines with same xy position but different z (for instance a cut-n-fill).
The only option that gave me a relatively accurate result was loft in combination with extrude.

Maybe I'm not doing it right though..

The Paul Aubin book is still not here. There is a 2010 version out and our order got upgraded to the latest version. A month ago it should ship in June, and now it says August...

[david_peterson]

Hi Eirik,
Did you try the help menu at all.
I know Aubin had some tricks on how to do it when he trained us. He was able to get some good results IMHO. Now if you're trying to render the site (which is what I'm guessing) The drape tool is more of a sketch than a true contour (IMHO). But if you have a 1' Z dir increments, you should be able to get some good results. There's a very specific order in which you need to use that tool to get good results, I wish I could still remember how he did it.

[neje]

Eric Using Drape you can create a contoured model of your site. I remember early on probably around release 3 they made much of the mass element modeler but little has been said for years but it is still there.
It will take some exploring but you can use drape to create the raw site as a masslement (I don't think it's a highbrid? but I could be wrong) and then use the 'Model Explorer' to use other masselements as negative to form your cut & fill. I have only just begun to explore the possibilities but it would seem to work. This allows you to cut with a very easily movable/adjustable object allowing adjustments as you design. Because little has been made of the massmdelling tool it hasn't attracted any development passed what was initially done but it's all there.

Driveways and paths - this is where it would struggle as how can you create paving that follows the contours. You could create copies of the main mass and cut out portions to give new materials for paving etc. This is where it's not so robust.

Alternatively there is a package called Easysite that was developed up to release 2006 but I know there is someone using it for later releases. It uses faces and looks a fantastic product for a great price but I don't think it has attracted the attention it deserved. At worst it's definitely worth a look because those that have used it think it's a great tool. I tried the demo only and didn;t get time or excuse to get into it but on quick review it seemed a great tool for the site niche without getting into Civil3D level of complication.

The Masselement modeller can be found under the design menu or in version 10 who knows - they probably forgot it! Type aecmodelexplorer in the command line and then F1 to explore help. There should be a good tutorial that explains how it works.

I posted another users example of doing this here
http://ausaca.blogspot.com/2008/06/drape-shadow.html

Let me know how you get on. I would like to explore this further but haven't had an opportunity that needs this level of detail.