AutoCAD Civil 3D

[#1]

Neil,

looking at your pretty picture there; isn't a MAPCLEAN going to delete one or the other of the endpoints on the magenta lines?  If so, that's not correct either.  Neither endpoint is right, the intersection of the lines is the point you need.

Sounds like we need some sort of TRIM & EXTEND command for surfaces, to find that intersection (or FILLET with zero radius).

[#2]

indeed and that pretty picture is only considering a 2D view, its even more complicated in 3D.

mapclean, snap clustered nodes is about the best approximation at the moment

[#3]

and as Allen said its worse as the offset increases.

[#4]

I just tried vk_topos method and it is pretty fast. But I do believe after creating the new offset surface a step or two should be added.

Setting it to show points only and extracting them so that MAPCLEAN can be used to consolidate the point clusters down to one point per cluster, and added those consolidated points to a new surface will give it a more accurate offset surface and smaller file.

I think until Autodesk adds this to Civil 3D, this will be my method of choice. 

[#5]

Archie, as Allen said: "The problem is that the solution would be the intersection of the 3D Faces.... Not the average of the endpoints."

So I don't see how Mapclean gets you a more accurate surface.  Smaller file, yes.  And probably no less accurate, but not more accurate.

[#6]

Guys:

I read this topic with interest and I have something to share.

If you have access to ArcGIS and the extensions Spatial Analyst and 3D Analyst, you can basically build a TIN on ArcGIS, convert to raster, and use the raster calculator to get an approximate offset, then convert back to contours. I used this procedure many times to do offset surfaces and tapered offset surfaces. I can post detailed instructions if you guys are interested.

[#7]

Guys:

I read this topic with interest and I have something to share.

If you have access to ArcGIS and the extensions Spatial Analyst and 3D Analyst, you can basically build a TIN on ArcGIS, convert to raster, and use the raster calculator to get an approximate offset, then convert back to contours. I used this procedure many times to do offset surfaces and tapered offset surfaces. I can post detailed instructions if you guys are interested.