Extracting partially intersecting solids

[kiarianc]

Civil 3D 2019.
I've been scratching my head all day trying to figure out the best way to select a large solid (original was several solids, now unioned) from another large unioned solid. 
As it's representing top soil cut from existing earth, it's jagged and non-uniformed (pink solid). 

What I want it to keep the cut solid (red), but any sort of interaction with this pink solid (the top soil cut), I want to trim off the excess earth cut. The point is that the top soil cut will be unchanged throughout the model and the earth cut will only ever show up underneath this topsoil cut. I will have no earth cut (red) showing above the top soil cut.

The custom sub assembly is supposed to do this already, but for some reason it's not. Any help and advice appreciated. Screenshot attached (sorry cannot post full model as it's a live ongoing model and more than my job is worth).

Thanks

[stevenh0616]

Hi @kiarianc,

From the looks of it you have two solids extracted from surfaces. One is your existing surface, the other is the design surface from the Corridor. Stop here and correct me if I'm wrong.

I'm understanding that you want to end up with 3 solids. 1 of the design surface, 1 of the existing surface without the cut caused by the corridor, and lastly 1 representing the existing surface cut.

The corridor itself won't do this.

What you'd need to do is make 2 new surfaces that have the existing surface pasted into it. Then extract the border of your Corridor surface.

For one of these, you would use this boundary has a hide - you may have to alter this boundary some to get to the extents of your existing surface as well. Once you hide it, you'll then have an Existing surface representing the removal of the cut portion from the corridor.

For the Cut surface, you would use this same boundary as the outer boundary of the surface. This will represent a surface of the Cut portion.

Once you have those surfaces, then you can re-extract the solids on those two surfaces and you'll have what you're after.

Does this make sense?

[kiarianc]

@stevenh0616 Hi, thanks for your reply. Apologies for taking so long to reply as I have been away. 
What I realise that I need now is I just need one surface to act as the slicing plane for another solid, but I have noticed that using a TIN created surface does not have the properties to do this. I think I went around a slightly long winded process of exploding the TIN surface into multiple meshes. then unioning the meshes to create a surface I can then use as a slicing plane.

The custom sub assembly I am using can create a 300mm Top Soil Cut solid, when you extract solids.
You first set the CREATESOLIDS command to description in the settings, and then can easily process this.
But what is happening is that this Top Soil Cut, although correctly taking off a 300mm strip, conversely the Earth Cut solid is not showing up correctly, sometimes this Earth Cut solid protrudes both in the same space and sometimes above from this Top Soil Cut Solid, which obviously makes no sense.
All Earth Cut solids need to be cut off as soon as it hits this -300mm imaginary line of where the Topsoil Cut interacts with the Earth Cut. Therefore, I just need one surface to act as a slicing plane, to slice this Earth Cut correctly.

In short, how do you efficiently process a C3D created TIN surface to act as a slicing surface that you can use in the 3D Modelling Tab's 'Slice' command. The slice command to my knowledge only works with a certain 'surface' but not a TIN surface. If any can enlighten me that would be much appreciated.

Thanks

[stevenh0616]

Hi @kiarianc 

Unfortunately there is no "slice" command for a Civil 3D surface. The only way around that is the workflow I mentioned in my first comment. You have a surface and you paste it into another surface and use boundaries (outer, hide, or show), multiple if necessary, to act as the clipping plane for where the surface would be 'sliced'.

In the past, I have drawn these boundaries using a number of commands/workflows. Some of these are the following:

- Use surface extraction to extract the surface Boundary

- Create a surface that stretches beyond where the it would tie into another (say a 4:1 slope, instead of targeting the surface I would project it beyond the surface to a distance at 4:1. Then use the minimum distance between surfaces command to draw the polyline where the surfaces would intersect.

- Corridor boundary extraction

-Then draw additional or use extracted polylines to join and create boundary line work

I have written some commands to help with some of these workflows in .NET to help the process go a bit faster, but unfortunately there is no simple 'surface slice' command to generate a surface.