Civil3D won't accept triangle as input (Drawing Objects)

[a_comenale5CSSL]

I've been using triangular 3D Faces as Drawing Objects for my surface definition for a while, but in the past two days I've been having problems with some. It came to the point where I'm not able to even create a surface using a single triangle, Civil3D won't create the TIN Surface and do nothing.

Does anyone know why this would happen? 

The triangles I'm using are vertical and I'm thinking the problem I have has something to do with it...

[neilyj666 · Accepted solution]

Got it in one - vertical objects cannot be added to a TIN as the algorithm doesn't allow it as how does the software know which is the correct Z value. Normally a very small lateral offset solves the problem but this would be a significantly more challenging with 3D faces.

[AllenJessup]

What is the source of your 3D Faces?

[a_comenale5CSSL]

Hello Allen,

Thank you for your reply. They're standard Autocad 3D Faces I received from the surveyors in our firm.

[matt_anderson_pe · Accepted solution]

A TIN surface can have many points, but none can occupy the same XY and two different Z elevations.

[a_comenale5CSSL]

Hello Matt,

that's what I thought. I guess this is due to functions in general being unable to return two different outputs with the same input.

[a_comenale5CSSL]

Thank you. How would you normally create a vertical surface? Without the offsetting trick that is...

[AllenJessup]

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@a_comenale5CSSL wrote:

Thank you for your reply. They're standard Autocad 3D Faces I received from the surveyors in our firm.

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What kind of Software are they using that creates vertical faces? Can they create a LandXML file for you to import? That would be better than 3D Faces.

[AllenJessup]

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@a_comenale5CSSL wrote:

that's what I thought. I guess this is due to functions in general being unable to return two different outputs with the same input.

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It's basically a Divide by Zero error. If the horizontal distance between the two points is Zero. Then the function fails.

[neilyj666]

It depends on the context, the originating data and what I was trying to achieve e.g. may be easier to model in vanilla AutoCAD using the 3D modelling tools available which will allow vertical faces 

[AllenJessup]

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@a_comenale5CSSL wrote:

How would you normally create a vertical surface? Without the offsetting trick that is...

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We don't. Usually you don't find a purely vertical Surface in field survey. The offset trick is used when designing retaining walls or foundation walls.

[a_comenale5CSSL]

They are using an Italian proprietary software/Autocad add-in called Civil Design...I'm in charge of producing the LandXML from the 3D Faces, unfortunately the software they're using won't export LandXMLs. 

[matt_anderson_pe]

The wall breakline (https://help.autodesk.com/view/CIV3D/2024/ENU/?guid=GUID-D9F76227-73D0-4467-9613-D9DEB4C8A3A3) uses an offset to allow this situation.

Just use a tiny offset.

[AllenJessup]

I have no experience with that software. However, I would be suspicious if I received field data containing purely vertical faces.

That would lead me to believe there was an error such as shooting the bottom of a wall and noting it was 6 feet high. Then someone creating a breakline by elevating a copy of the bottom of wall by 6 feet and not allowing a slight offset. The chance of locating a point so directly above another point (as far as the software is concerned) is extremely unlikely.

So if you're dealing with field data. The chance is the difficulty is in the data. Not the software.

[neilyj666]

The only other possible workaround I can suggest is if you can identify the 3D faces (say the lower ones) such that you don't have the verticality issue and try to build the TIN with those and then build another TIN with the upper faces.