topic Re: Extrude a 3d polyline to a fix elevation in Civil 3D Forum

Extrude a 3d polyline to a fix elevation

qchenTPPXV — Sun, 01 Oct 2023 19:09:18 GMT

Greeting,

I have a 3d polyline at the bottom and want to extrude to a fix elevation(6 m). Is there a command to do that? I tried to create another surface at the elevation of 5m and use it to trim the original surface. However, it doesn't work for me.

Any help would be appreciated.

Re: Extrude a 3d polyline to a fix elevation

Pointdump — Sun, 01 Oct 2023 19:19:55 GMT

Hi Qixing,
More details please. What end result are you needing this for?
Dave

Re: Extrude a 3d polyline to a fix elevation

qchenTPPXV — Sun, 01 Oct 2023 19:33:35 GMT

Yes, the 3D polyline is on the bottom, attached to the bathymetry. I want to create an extrusion to represent a turbidity curtain. So the top of the extrusion is at the elevation if 5m and the bottom is the 3D polyline.

Re: Extrude a 3d polyline to a fix elevation

rl_jackson — Sun, 01 Oct 2023 20:26:48 GMT

This is not possible you CAN NOT have a x,y=x,y with different z values there must be a slight transition. There must be a slight lean so that x,y,z=x-.001, y-.001,z

Re: Extrude a 3d polyline to a fix elevation

qchenTPPXV — Sun, 01 Oct 2023 21:09:35 GMT

Yes, I see. Is there a way that I extrude the bottom 3D Polyline that is higher than the evaluation of 5m, for example set the height of 6m for extrusion. So that I can use a surface to trim it. Just don't know the workflow for that.

Re: Extrude a 3d polyline to a fix elevation

neilyj666 — Sun, 01 Oct 2023 21:26:00 GMT

Are you referring to Civil 3D surfaces or vanilla CAD surfaces - same names but very different?

Re: Extrude a 3d polyline to a fix elevation

Pointdump — Sun, 01 Oct 2023 22:07:54 GMT

Qixing,
I still haven't figured out what you're going to do with it.
Copy your 3D polyline @0,0,6. Convert the new 3D polyline to a 2D polyline and change the Z to 6 in properties. You can use that to trim the "curtain".
Dave

Re: Extrude a 3d polyline to a fix elevation

qchenTPPXV — Sun, 01 Oct 2023 22:30:35 GMT

When I extrude the 3D poly line, the property shows “surface”. I think it is not a typical Civil 3D surface.

Re: Extrude a 3d polyline to a fix elevation

v-silvestre — Sun, 01 Oct 2023 22:52:16 GMT

Hi @qchenTPPXV, You can use the command OFFSETFEATURE. This works with polylines, 3d polylines, parcels, featurelines & survey figures. You will have to add an offset distance because like what others have mentioned you can not have sheer vertical faces within Civil 3d surfaces, but you can specify something really small like .01. We typically do this for curbs, walls, exposed slabs; just situations where we need something vertical but with a slight angle. Make sure you offset towards the inside of your 3d polyline.

After selecting your horizontal offset, you can now specify your vertical offset, you have the choice of: Slope, Grade, Difference, Variable or in your case Elevation.

In the picture above, I just converted the 3d polylines to feature lines and used those to define the surface. The bottom feature line has varying elevations, but the top is all set to one constant.

Re: Extrude a 3d polyline to a fix elevation

qchenTPPXV — Mon, 02 Oct 2023 01:54:07 GMT

Yes, I tried to use this method.

To trim, first select the surface then the 2D polyline at 6m, but for select the area to trim it doesn't work. I select the upper part of the curtain but didn't get it.

Re: Extrude a 3d polyline to a fix elevation

neilyj666 — Mon, 02 Oct 2023 07:11:20 GMT

@qchenTPPXV @Pointdump the screenshot shows a vanilla CAD surface - these can't interact with a Civil 3D Surface; as I stated previously same name but very different objects and you cannot use the vanilla TRIM editing tool.