extracting contours

[ray isaacs]

is it possible to extract contour lines (say as 3d ploys) from a dtm? if not is there another way to generate landform data from a dtm that can be usefully exported to other formats, such a dwg?

cheers,

ray

[Bryan G.]

Ray, this is something I have wanted to play with for a while. Are you planning on sending the contours to a CNC cutter for modeling?

[Mark Mullany]

Hello,

There is probably a much better way to do it but in the wee example file I just made you can look at in Top plan with the 2D contours setting without labels and simply Ungroup it - this leaves you with a series of flat polylines. This seems to be the same as exporting it directly only then it becomes a Block. Would that suffice? or would you like to retain their 3D heights?

If your going to have a go at this make a copy of your model first or you'll lose it.

Alternatively have the 3D part show as extruded contours, use extract to extract the contours (fiddly),or use the extract tool to extract faces to give you NURBS, or use the 2D polygon tool in paint-bucket mode and click on the top face of each level, then you can minus out the parts you don't need and convert to 3D polys. This is ok for simple ones.

I imagine there are other ways to do it. hopefully someone with more experience in site models will get back to you!

[Tamsin Slatter]

How about putting the Site Model into a 3D view and setting its 3D Style to 3D Contours. Make sure you are showing the Proposed model (if that's the contours you want!)

Copy the model (because you are about to lose it completely otherwise.) Then, choose Modify > Ungroup.

You will be asked if you want to ungroup high level objects. Answer Yes please! The result will be a bunch of 3D Polygons that represent the contours.

[ray isaacs]

thanks, everyone, for the input. tamsin's suggestion works in a straight forward way and the 3d ploys convert easily to dwg. i haven't checked thoroughly, but i imported them into rhino and they seemed to be in the right place. further investigation will show how well scale, elevation and geo-referencing transfer. but, for now i'm happy.

bryan, the cnc issue is interesting, but we are looking at how we are going to exchange model information within a workflow using as many as five different software applications. exporting the dtm directly was not working well in most cases, hence the need for 3d ploys.

cheers,

ray