Problem offsetting a spline

[Anonymous]

Hello,

I'm just getting used to Civil 3d after using an old version of AutoCAD for years.

When drafting a topo I've created a spline from point to point on the centerline of a winding path and need to offset in either direction. When I go to offset the spline I get message that says I can't because "To offset an object, all points in the object must be located in the same plane." After playing around a bit I found that if the spline is only connected to three survey points it will offset fine but any more and I get that error message. What's going on here? How do I get around this?

Thanks

[neilyj666]

I/'m not very familiar with splines and rarely use them but you could convert it to a polyline and offset the polyline?

[Jeff_M]

I don't use splines, so don't know if you can place the control points at differing Z values. Although it sounds like that's exactly what's happening.

When creating the spline, try making sure that OSNAPZ is ON so the elevation of the point won't be used. This will insure the spline is in the same plane.

[antoniovinci]

Before offsetting that spline, try to _FLATTEN it: any changes?

[ralstogj]

The basic offset works in a 2d plane, Mathmatically a plane surface in space is definited by 3 x,y,z points i.e  a triangle is the simpliest form of a plane. You have more than 3 z elevations along the spline therefore the spline is not drawn on one 2d plane. Maybe look at using featurelines and then a setted offset. 

[Anonymous]

TRY FLATTEN 

[jmayo-EE]

In recent versions the flatten command has not be doing the conversion for me.

The Convert 2d to 3d Polyline command does work. See the attachment.

[Anonymous]

Thank you very much. It works perfectly.