Trim Surface to another Surface

[Postmaster_G]

I was wondering if there is an easy way to trim one surface to another.  Right now, I have two slopes (3:1) that are perpendicular to each other. They meet at a corner and I have extended them past eachother so that I could see the intersecting edge.  Now I would like to trim them to each other like you would a polyline etc... but I am not sure how to do this.

If I select surftrim, it tells me they are the wrong object type, but they are tin surfaces?

This would really help me a lot, thank you!

[troma]

Use the MINIMUMDISTBETWEENSURFACES command to find the line of intersection.

Then use that to create boundaries for each surface.  Add as a non-destructive boundary to trim the surface off at that exact location.

[Postmaster_G]

Your suggestion has worked.  Under 3D Modeling workspace If you go into the ribbon -> surface -> edit -> and hover over the trim command, it shows a video of exactly what I want to do.  I created the surface from featurelines, and it is a tin surface.  I am not sure if either one of those things will effect the operation.  Does it have to be a nurbs surface?  If so, why can't I convert my tin surface to a nurbs surface?

[troma]

I've never heard of 'nurbs'.
If that is a basic 'acad' 'surface' then there are some convoluted half-remembered ways in the back of my head to make that conversion. Do a web search for "convert TIN surface to autocad surface". But that might be too much work, seeing as the other suggestion has already worked for you.

[troma]

Is this what you're looking for?

[neilyj666]

Non Uniform Rational B Spline (NURBS) - used in vanilla AutoCAD rather than the TIN in Civil 3D

[Anonymous]

Create a surface and name it "Combine". Go to Definition > Edits > Right click > Paste Surface > Select your 2 surfaces (can only select/work one at a time) and you have a surface trimmed at where the 2  intersects.

cheers

[Baker_ADG]

I have created a Tin Volume with the 2 surfaces. Then added a custom contour at elevation 0 then extracted it. 

[wilsonm2000]

I don't have access to C3D right now so this might be a lot of BS, but maybe once you get your MinimumDistBetweenSurfaces featurlines, you could add these to a surface as breaklines, this will give you a datum surface (shown in red below, red dots is featurelines created by MinimumDistBetweenSurfaces), then convert the 2 existing surfaces and the new datum surface to AutoCAD surfaces.  Then use the datum surface to do a SURFTRIM on the existing?  Not sure if you can tell the command to trim everything above/below the datum surface?

[mhogewind]

This works if you have 2 surfaces. I am in a situation where I have 4 surfaces civil 3D surfaces - that each resemble a utility trench - overlapping and want to create an overall surface which is trimmed to only show the deepest trench in each scenario. the SURFTRIM command is also dynamic which will come in handy if one of my trench surfaces change.

I have tried using the SURFTRIM command and am still getting the "Not a valid object type". Do I need to/how do I change my civil 3D surfaces to 3D "face" surfaces? 

[neilyj666]

Don't confuse Civil 3D surfaces with regular CAD surfaces they are totally different objects that don't talk to each other.

The problem I have found with creating a plain CAD surface from 3d triangles (extracted from a Civil DTM Surface) is the number of triangles will cause a hang and need to use Alt+Ctrl+Del to shut Civil down.

The Civil way to do this is via boundaries on the DTM surfaces but this isn't particularly dynamic unfortunately and is quite tedious. It is unfortunate that DTM trimming/editing in Civil is nowhere near as advanced as vanilla CAD.

[mhogewind]

Thank you for the quick reply.

Not really the answer I wanted to hear but at least I can stop chaising the rabbit now. Would this be possible in Vanilla CAD? 

[neilyj666]

It'll depend how complex your utility trenches are I guess - I'm not too familiar with the Vanilla CAD Solid/Surface./Mesh commands and just know enough to get by...!!!!

If you could share your drawing there are many others here who may be able to suggest a workflow