Slicing a 3D Solid with a TIN Surface

[5stringb]

I'm trying to calculate a volume of soil to be removed from a dig.  I have a point cloud with ground shots from existing grade.  For the sake of simplicity, let's say I have a square box with (4) walls and a basement slab, dug into the Earth.

   Here are my steps:

1. Create a TIN surface from the point cloud to represent existing grade - no problem.
2. Create a 3D solid from an (around-the-walls perimeter) 2D polyline, extruded upwards by the height of the walls - no problem.
3. Align the (uneven) existing grade TIN surface properly near the top of the walls based on a reference elevation point - no problem.
4. Use the TIN surface to Slice off the top of the 3D solid, leaving the uneven top surface, square sides, and square bottom - Having trouble here.

I can't seem to use the TIN surface to clip the 3D solid.  Help?

I'm also open to more efficient workflows and ideas on how to accomplish, so if I'm doing this the hard way, please advise.  Thanks!

[neilyj666]

Be sure not to confuse an AutoCAD surface with a TIN surface - they are two different objects; although there is/was a tool in the app store that could do this task. I'm not in front of civil until tomrrow so can't check.

I would build the solid as a TIN surface using feature lines with a nominal offset  (10mm) to avoid vertical sides and use minimum distance between surfaces to find the intersection at ground level.

Another option is to use a featureline for the bottom of the excavation and grade up at an appropriate angle, infill the grading and compute the volume

[WarrenGeissler]

Step 1: Select your surface and use Extract from Surface: Extract Objects - Choose Triangles - Select from Drawing (area of interest)

Step 2 - Use PLANESURF - Object - Select your resulting 3d faces 

Step 3 - UNION the surfaces together

Step 4 - Use SLICE on your solid - Surface option

[neilyj666]

I'll be trying this tomorrow.....

[WarrenGeissler]

Instant 3D curb inlet 

[Jowennl · Accepted solution]

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@Anonymous.geissler wrote:

Step 1: Select your surface and use Extract from Surface: Extract Objects - Choose Triangles - Select from Drawing (area of interest)

Step 2 - Use PLANESURF - Object - Select your resulting 3d faces 

Step 3 - UNION the surfaces together

Step 4 - Use SLICE on your solid - Surface option

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Hi Warren,

This is an excellent solution. I personally haven't had the chance to cut a solid from surface tin before so I did exactly what you suggested and it is spot on. Thank you for sharing the workflow.

I just have one suggestion in Step 2. Instead of using PLANESURF I would recommend using CONVTOSURFACE command. Reason for this is that using PLANESURF - you will have 3d faces remain intact after creating the surfaces but using CONVTOSURFACE it creates the surfaces but deletes the 3d faces as well. But all in all your solution rocks.

Step 1: Select your surface and use Extract from Surface: Extract Objects - Choose Triangles - Select from Drawing (area of interest)

Step 2 - Use PLANESURF - Object - Select your resulting 3d faces  or Use CONVTOSURFACE

Step 3 - UNION the surfaces together

Step 4 - Use SLICE on your solid - Surface option

See attached animated gif as I test this workflow. (SolvedByWarrenG-SliceSolidFromSurfaceTin.gif)

Cheers,

Jowenn

[WarrenGeissler]

Good catch Jowenn! What are you using for your video? I'm curious why you didn't use Screencast?

[Jowennl]

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@Anonymous.geissler wrote:

Good catch Jowenn! What are you using for your video? I'm curious why you didn't use Screencast?

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Hello Warren,

I use screencast if I intend to talk about the video I am creating and I use ScreenToGif if I just want to do a very quick demo without talking. I also don't want to over populate my screencast and have no space available in the future as I like creating screen captures for future reference. I just save all the animated gif in a hard drive that I can remind my self later on.

Cheers,

Jowenn

[neilyj666]

@Jowennl The gif was extremely useful - I can see a few immediate uses for this workflow...

[5stringb]

Thank you both Warren and Jowen.  I've spent a few days working with this method, and adapted it to my process.  Big kudos to you both!  I now have a flexible process that can be adapted to multiple projects.

TIN => Surface => Slice => MassProp

[PeterKozub]

hi

"I'm trying to calculate a volume of soil to be removed from a dig"

Create a 3dpoly around the footing call this surface Surf_bottom_Footing

Next tin a surface volume to og or fg whatever

This volume will not take into account any safe slopes to make job site stable ie

1:1 of toe footing.

I would use gradings for more complex shapes at 1:1 safe excavation slopes

depending on depth of cut

Peter

[PeterKozub]

OOps 

forgot to mention that

I use mass prop for concrete volume calculations

massprop never seemed to have a home in civil earth works 

Pete

[Anonymous]

I am trying to slice my solid (a terrain model) with a curved surface (the geological boundary), but the action failes. Does anyone know why?

[5stringb]

A couple of things you might check...

Slice only works with ACAD surfaces, not TIN surfaces (just in case you were trying that).  So your curved surface needs to be an ACAD surface, not a TIN or a Grading.  Also, the surface should extend beyond the solid at every point.  Make sure you don't have any surface edges intersecting your solid.  If they're close, zoom in and check.  If you do, you'll need to extend or extrapolate your surface beyond the solid at every point.  Also, this is obvious, but you need to choose the "Surface" option when you're slicing.  If this doesn't solve your problem, please reply with some more details about exactly what's going on. 🙂

[Anonymous]

Hi,
I have made sure of the checkpoints you posted, also with the difference from TINsurface to just surface.
I am wondering if the "Slice" action requires a flat plane to slice from, as my methods work if I make a flat plane to slice the solid with.
However, I would prefere to be able to use a curved surface to slice from, as it would increase the accuracy of my model.
Se attached printscreen;
[cid:image001.png@01D47BEF.FB47E4A0]

Cheers, Tord

[neilyj666]

It will easier to advise if you are able to attach the drawings

[Anonymous]

Can u see this attached png photo?

[5stringb]

From your photo, it looks like your curved surface is a series of plane surfaces stitched together.  If that is correct, you should try making copies of them all, and union the copies together into one surface.  ACAD sometimes gives you a warning if you try to union surfaces together, but it works for me anyway.  Just make copies first so you have backups of your individual surfaces.  Also, on your curved surface, it might be a situation where one or more of the individual plane surfaces you used to create the curved surface, don't intersect all the way across their faces.  Further, it appears that your curved surface doesn't actually slice across the solids, but sits near flush with them.  I can't really tell from the 'plane view'.  In the yellow area, it looks like the surface is on top, but in the green area, it's beneath.  There are several things I can't tell from the info you've given us so far.  Are you trying to slice these from left to right, or for elevation (above and below)?

[neilyj666]

...as I said supplying the dwg will take a lot of the guesswork away whilst attempting to find a solution

[Anonymous]

The goal is to slice from surface and down on an angle (in this example, i think it is 70 degres)

Attached is the dwg. Sorry for not doing so sooner.

As you said, they are initially plane surfaces, but i used "union" on them making them one surface. The surfaces are also made from featurelines placed on the terrain model (top of solid). So there is a chance they do not cross over the terrain model. However, this did not affect my plane surface so i did not think it would be a problem on the curved surface.

I hope this helps, and thanks for the feedback 🙂