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skavan

The A, B, C's of DWG to Terrain

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Hi,

I have a dwg file from a surveyor. It has a lot of layers, - but two of them are contours made from 3D POLYLINES.

If I import the dwg, the polylines come in flat - unless I force import to >Convert Objects To "ALL 3D".

That now brings in a set of polygons with thousands of vertices (100,000+). While I can create a terrain from this, it's dense and very slow to then manipulate. I was thinking, I should be converting the polygons to 3D Stakes or Loci (not sure which). But first, I'm guessing I should simplify down my vertices??

Anyway - I'm stuck on what the correct steps should be.

In sketchup, I import the polylines. Simplify them (simplify contours) and then create a terrain.

What's the VW way?

Thanks in advance.

s.

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The Simplify Poly is great and getting better and is the normal Vectorworks Way. But it sometimes distorts the contour more than is acceptable.

Another way is to make a new point cloud to create the DTM.

Use a 3d locus and Duplicate Along Path. Each of the imported Contours (2d or 3d) is a path. In the DAP pref, set the number of dupes or spacing so that the dtm is manageable. An accurate dtm may only need the major contours.

Class each "seed" locus before the running the DAP - new class for each contour. Then each contour bunch is easy to select and raise to z as needed. Class names can be descriptive eg Contour-100m, Contour-110m, etc. Class colors can be helpful, too.

I think this works with Stake objects, but I never tried it. File size and responsiveness might be a problem.

Another way to reduce the contour vertex count its to trace the imported contours with the 2d polyline spline tool or the NURBS curve tool. Then convert to 3d polys and create the DTM.

-B

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thx guys.

one more question. once created, I'd love to be able to extend certain axes of the DTM (i.e. extend the model eastwards and westwards) at the same elevations as exist at the defined edge. Is this possible - and if so - how?

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You can extend the DTM edge profile in several ways. The starting point is to isolate the hull of the DTM. Select/copy the DTM and paste in place to a new layer or, better, a new blank drawing file. You can paste it in place back into the orig file.

Select the DTM and set 3d display as 3d Mesh Solid (this one has a hull)

Convert to Group (Cmd K) which yields a group.

Enter the group to find two more groups, the DTM and the hull

Delete the DTM

Ungroup the Hull, select all and convert to 3d Polygons (there may be hundreds of them, because curves are interpreted as facets). Delete the ground plane polygon leaving just the "walls" of the former hull.

Add Solid so you don't have to work with the individual polys. This may not work at first because there may be some overlapping polygons, most likely a little bitty extra one in one or more of the corners. To investigate, marquee a few of the polys around a corner and try Add Solids. If no good, zoom waaaay in and delete that little 3d poly in the corner. May take some trials & delete as nec until the whole bunch of them add into one big solid.

Now you can select the faces and shell them. They might not shell all at once, so you have do them individually and create new solids to fill in the "pieces of pie" at every corner. I only did one one in the example - it's pink.

Or you can work with the top edges of the former hull to make a surface extend out from the DTM.

Post back with your results.

-B

ubbthreads.php?ubb=download&Number=10061&filename=DTM%20&%20Hull.png

ubbthreads.php?ubb=download&Number=10062&filename=Shelled%20Faces.png

ubbthreads.php?ubb=download&Number=10063&filename=Surface.png

Edited by Benson Shaw

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crikey - thanks for the great insight. I think its a little beyond my VW skills right now - so I cheated and moved the dwg source file into sketchup.

I used Sketchup's simplify contours routine to trim the data points on the 3D Polyline contours.

I then locked the contours into a component and created a new polyline around the perimeter of the contours.

Next step was to scale the 3D polyline in the X and Y directions by the required amount (30').

Finally I exported from sketchup in dwg format and loaded it into VW 2014 - and hey presto. Success (I think).

I will try your suggested method when I get a bit more up to speed with VW.

THANKS!!

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