Friday, May 15, 2009

AutoCAD Civil 3D 2010 Selecting feature lines, osnaps, and starting elevation

At Hubbard Engineering, when we want to draw a feature line over background geometry, continuing an existing feature line, what we do is use osnaps to select the endpoint of the existing feature line. But AutoCAD Civil invariably snaps to the underlying background geometry.

We found a solution, but first, here are some non-working solutions: We tried (out of desperation) adjusting the OSNAPZ variable (1 ignores Z in osnaps, 0 uses Z as out of the box). That doesn't work. We tried tweaking DRAWORDER. That doesn't work. We tried turning down VIEWRES to make arcs clunky. That works, but only for arcs, not lines.

We currently have two competing solutions:

1. Put the feature lines on a layer that has a complex linetype you can pick. On the fly, we used our ------X--------X-------X------- fence linetype. This works very well in all cases except short arcs and lines. We may define another "feature line" linetype that repeats more often.

2. Use our custom OFI (OFF ISOLATE, LAYISO) command to turn off all layers except the feature line layer. Then after starting the feature line, use the layer palette to turn on all layers again before continuing the feature line. This is relatively quick and painless if you select all layers using CTRL+A and then click any light bulb in the ON/OFF column.

At least those two solutions are keeping us moving forward happily.

Follow-up July 17, 2009

3. Osnap to a Spot Elevation label (I use the Center osnap) at the point in question.

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