I I have a pretty big topo that i want to patch. It takes forever and crashes. I want to patch it and make contours (in u och v directions) for later use in illustrator to make a simplified yet characteristic diagram of the site? diagrampatch.3dm (12.4 MB)
This is the type of data I deal with (virtually) every day. Patch is not the way to go to get a surface from that data, it will just hang Rhino.
Here’s what to do:
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Use SelShortCrv with a value of about 50, then take the 5,000 or so curves selected and put them on another layer and turn it off. That will leave about 1300 or so decent curves.
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Call ExtractPt on all the remaining curves. While the points are still selected, call the PointCloud command. That will turn all the points into one easily managed object.
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With the point cloud selected, run the MeshPatch command. Just press Enter when it asks for holes. It will produce a terrain mesh virtually instantly.
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Now, if you really need a surface, in the Top view, Zoom Extents on the mesh patch, then call Drape.
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Set Autospacing to no, and set the U (X) points to something like 400, and the V (Y) points to something like 250. Then pull your drape over the mesh making sure to stay inside it.
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You will now have a sorta nice surface with lots of UV lines that approximates your terrain.
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You can use a smaller UV count to make a smoother surface but which will not fit the terrain as well.
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You can also use Smooth on the resulting surface to smooth it out, or even Rebuild - both of which will smooth the result, but also be less accurate of course.
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For closeness to the original data, staying with the mesh is the best, the mesh will actually pass through all the data points (i.e. your contour polylines).
HTH, --Mitch
2 Likes
Great tip! is there any way to exagerate the landscape a bit, the height in a quick way?
hi
if it doesn’t have to be exact you could simply just use scale1d on the geometry after you created it
Hi
great tipp! I have tried this in the past and it was a real pain so far. will keep this in mind next time i need to do this 
Great!!!