Creating Terrain surfaces in AutoCAD

[ericmiles]

Hello,

I'm using AutoCAD 2008.

I need to do an analysis that requires me to have a 3D terrain surface in autoCAD. I have poorly "hacked" one together myself from contour lines in the past, but am trying to do it properly this time.

the cadTutor site has a tutorial on KEY terra-firma, which appears able to do exactly what I want. However, before I purchase that product, can anyone recommend any other programs or methods?

cheers,
eric

[SLW210]

See "Similar Threads" at the bottom of this page and do a search for Terrain Modeling.

[ericmiles]

thanks, I'll poke around

[ericmiles]

It appears that outside software is essential. I have Global Mapper, which is a cheap GIS program, which is how I did it in the past. It spits out what I want, sort of.

The scales between lat/long and elevation are always off. Is there a straightforward way to change (in this case squash) a 3d mesh in the z direction while preserving the x and y directions?

thanks,
eric

[SLW210]

See if THIS thread helps.


I will move this to the 3D section for you.

[ericmiles]

Thanks for the help,

Between what I know, and what you just showed me, I know how to make happen what I want.

especially big thanks for the quickness of the replies,
eric

[rustysilo]

What sort of analysis are you doing?

[ericmiles]

I'm doing an analysis of radar coverage in the vicinity of wind farms. There's probably an easier way to do what I'm doing with GIS, but I'm not such a GIS stud. And analyzing different radar beam patterns (vertical and horizontal shape) seemed easier to do in AutoCAD with my skill set.

Now that I have the terrain maps in as a 3D mesh, the analysis is relatively straight forward. I was getting a little tripped up because the transfer from my mapping program was putting the x-y coordinates in lat/long, and the z coordinates (terrain altitude) in feet. There were also some artifacts along the edges (values of -99999.). The combination of the whole mesh being extremely stretched in the z-direction, and the edge artifacts made it very difficult to see what was actually going on.

Once I figured out what I had, it was relatively straight forward to clean up. I changed the export bounds in my mapping program so that the bounds didn't fall off the edge. I turned the mesh into a block, reinserted it with the appropriate xyz scale factors, and exploded it back into a 3d mesh.

I use Global Mapper as my mapping program. It was only $300. And though it doesn't have the ability to perform many of the more advanced functions of other GIS programs, it's extremely easy to use, and absolutely excels at converting between different data formats.

cheers,
eric

[ericmiles]

wrote with a little to much confidence in my last post . . .

I'm using m2s to solidy my terrain surface, so I can subtract it off with a plugin.

So far, when I run m2s, when it starts computing (I think) it prints out 0.000000 and then does nothing.

Is this normal? I've never used lisp in autocad before, but I beleive its loaded properly (it takes me through the mesh selection and thickness choices)

any tips? thanks,
eric

[CarlB]

It's possible mesh is larger than it can handle, or some problem with the mesh geometry - but I would have expected it would generate some error message.

Could you somehow divide mesh into smaller parts , run lisp on smaller mesh, see what that does?