Civil/3D model

Alij

Hi, I have spot levels that I have externally to a building. I can surface and create a tin/terrain easy enough but as the levels are not overlapping the walls and often just outside, how can I extend the true surface further so that it overlaps the external skin of a 3D model of a building so that I can then trim the external wall line to the terrain? Is there a easy way of extending the surface?

If the terrain was flat I am sure it would be find to just extrude to the adjoining triangles that cross through the building, but if the site is very sloped if I do this I will end up with levels thats arent true to the site.

Not sure if I am clear here?

Virgil

Hello.

I am not sure if I correctly understood.

From the pictures, it seems that the surface is below the building.
So, maybe, the building should be extended downwards, to make contact with the surface?

Or, maybe a grading (digging) should be modelled using the building contour?
Then, extending the buidling downwards would be easier.

Alij

Hi Virgil, thanks for your reply.
I can easily extrude the building corners to the interpolated surface but this would then create false levels at the building edge. Just a quick picture


I am hoping there is a way to grade the topo surface or exent it out to just beyond the building face so then I can trim it a lot more accurately.

ALANH

You need to look at Breaklines as the name implies it breaks the 3dfaces along the line into new 3dfaces. So would just use a 2d pline of the base of the building. You could then remove any tin inside the building or make a new surface by removing points from the tin inside the building. There are some more steps you can do to make the building part of the Tin. You just have top of building with Z's but 0.01 inside the floor shape.

Alij

Yes but how do you extend the surface on its grade each side to that new boundary?

Virgil

Hello.

You could experiment with working with a grading.

As contour, the building contour could be used and placed on a plane at the bottom of the walls.

Then a grading could be created starting from this contour, by using the GRADING command.
This operation will perform a cut where the TIN surface is above the contour area, and a fill where the contour area is above the TIN surface.

Alij

Thanks Virgil,

I will look into this.

I have found a couple of instances of people asking the same on Civil 3d/Autodesk and will see if I can use any of those the solutions also. Thank you for taking the time to respond, ....and you also Alan.