Clipping shape from site model

[Poot]

Hi everyone,

I am wondering if anyone has a routine for clipping out a shape (hole) from a site model. I don't mean using a site modifier to shape a lowered flat area, but as if cutting a hole directly from the site model which will remain empty.  

 

The purpose is to have a larger site model of the context, with a space for the site model of the project to fit into.

 

Is this possible?

[Tom W.]

@Poot I tried this recently + couldn't find a way to punch a hole clean through. I ended up creating the site model in two halves + joining them together.

[Poot]

 

1 hour ago, Tom W. said:

@Poot I tried this recently + couldn't find a way to punch a hole clean through. I ended up creating the site model in two halves + joining them together.

 

Did that work to have a clean, empty hole inside the site model?

[Benson Shaw]

The DTM changed a few versions ago.  I used to be able to Solid Subtract solid volumes from a DTM. Result was a Solid Subtraction, rather than a modified DTM.  Now it seems rather undoable.  Ungroup a DTM in mesh mode (result is several objects/ groups - surface mesh, hull, contours) and even the mesh seems unresponsive to solid sections or subtractions, conversion to NURBS surface, etc. ???

 

So, another option to the 2 halves suggested by @Tom W. .

I know, you didn't want to do this with a pad, but it works.:

 

Duplicate the large DTM to create one for project, other for surrounding context.

Crop one to the project boundary and isolate this to a separate layer or another file entirely for work on the project site.

 

Modify the context DTM with a pad in shape of the project boundary crop. Set the pad elevation at or below the bottom of the mesh skirt. Pad with Retaining edge does not clip as well as using a pad with custom grade limits, eg offset the Pad source by 1mm or less.  Update the DTM. Duplicate to another layer just in case. Ungroup the DTM, delete the skirt and contours.  This should leave a mesh surface surrounding your site.

May take some fiddling.

 

Reference this to your site.  Good luck.

 

-B

 

 

[zoomer]

That should work.

 

I think I did it just by a Modifier with a Grade Limit, offset only a few centimetres.

The 2 DTMs won't interfere and no one will notice the sub terrestrial mess.

 

VW DTMs or any other TIN can't ever have any really vertical borders inside the

DTM, just for its borders outside. So you always have to give some minimal distance

in YX.

[Poot]

3 minutes ago, Benson Shaw said:

 

I know, you didn't want to do this with a pad, but it works.:

 

 

Yes, I just thought there was a way to subtract from that surface as you can in programs like Rhino. 

The two half method will be a way to do it....but it does seem simple to make the dtm with a pad. I was hoping to avoid a mess underneath the surface, in the case it was ever exported for IFC or something down the line.

[Tom W.]

Yes I was trying to do it without the mess under the surface. It was just an experiment really to see how I would backfill around an excavation for strip foundations so I was looking for something like this:

Where the two halves joined it looked like this for some reason:

Despite both sections being exactly the same size.

But I didn't worry too much because it wasn't noticeable in the wider context + I was only doing it for fun really.

 

[Jeff Prince]

What's all the fuss about 🙂

 

[Tom W.]

Ok cool how did you do that?!

[Jeff Prince]

@Tom W. @Poot

By listening to Devo....

 

 

 

Smack that clip
Use this nifty trick
If the shape is whack
you'll break your model’s back

 

When a problem’s put to song
You must fix it
Before this post gets too long
You must clip it
and when a site boundary is wrong
You must clip it

 

Now clip it
Into shape
Shape it up
Get straight
forgo curves
Connect to an edge
Try to select it
It's not too late
To clip it
clip it good

 

But when a window’s facing wrong
You must flip it
Never mirror it around
instead you should flip it
Won’t face the right way
Until you flip it

 

okay, okay, enough 🙂

Now for an extreme example of site model clipping....

 

These are two different site models, left with text connected to the outermost boundary, right just an example of the hole shape alone.

 

In this clip cube view, you can see my connection to the right of the model.

 

but here in plan view, these connections are simply thin lines. Prior to building the model, these could be further reduced with site model settings such as turning off the skirt and site model border.  Using classes for those features might even let you just turn them off by class.

 

The secret to working around this limitation of putting a hole in the model while maintaining it as an actual DTM is to:

• leave the original site boundary intact
• place your desired hole
• and then connect it to the existing site boundary with a really thin rectangle using "add surface' to create a continuous boundary since you can only have one boundary in a model.  Tricky huh?

This creates the illusion of the hole.  If you look at the image with the site model shown with a text shaped hole in it and compare it to the clip cube view, you see how I connected it to the site boundary.  This site is 500'x500', the letters are 6' wide, and the connecting rectangles are only 1 inch wide.  So, the slender connecting shapes are hardly noticed, especially on a large context model.  In the original post I made, the connecting rectangle to the circle was 0.1 inch wide on a 1000'x1000' site.  This connection to the site's outermost boundary could be further camouflaged by placing it along a feature such as edge of roadway, property line, etc.

 

You can do curves, but too many of them or complex curves will lead to problems.  As I was mocking up this example, the Arial Bold font that I converted to polys had Bezier curves and this proved to be too much to process.  So, I just used rectangles to form my shapes in this example.  A simple circle or a few curves won't kill it, but complex text sure will.

 

I stumbled upon this method last year when illustrating how to clip a site model.  I cut a roadway and culdesac out of a model in that example, so I reasoned I could just put the "roads" really close each other to cut a hole anywhere I wish for this thread.

 

Now clip it,

clip it good

 

 

[Tom W.]

That's fantastic @jeff prince thanks as ever for sharing. I'll be checking my old Devo albums for more site modelling tips now 😁

I was worried when you said leave the original site boundary intact it wouldn't work if I clipped the boundary too but it does so that's really really cool. If I want to I can backfill around my building now with a single 'backfill DTM' rather than two joined together.

And if you ever get to sculpt 30' high Devo lyrics in someone's lawn for real be sure to let us know 😊

[Benson Shaw]

Ha! that's good, @jeff prince !  As usual.

 

Actually, the DTM can be cut via Solid Subtraction or Solid Section.  Or, the DTM can be ungrouped resulting in a mesh (which can be cut), the skirt elements (unless skirt switched off in DTM Settings), and a group of 3d contours (unless 3d contours switched off in DTM settings).  The Solid Section operation takes some patience with the spinning beachball whilst calculating every point in the mesh.  So, not for the faint of heart or dearth of compu power.

-B

 

Edited April 24, 2021 by Benson Shaw
details, schmeetails

[Poot]

WOW.    A huge thanks for multiple approaches to this @jeff prince @Benson Shaw @Tom W. !

I will try them out!

[Jeff Prince]

@Tom W. Happy to hear it was helpful.

 

  @Benson Shaw I think you are starting to recognize the theme to some of my solutions. These are usually inspired by those beach ball moments 🙂

 

[bob cleaver]

can we nominate this thread for the VW hall of fame ??

Mixing real world sound (DEVO) and graphics (VW) deserves a prize 

[bob cleaver]

and a backup by Benson who always comes through is a bonus 

[bob cleaver]

Weird Al Yankovic (who went to Cal Poly SLO for architecture) has nothing on Jeff P

[Jeff Prince]

@bob cleaver I consider that high praise 🙂  I grew up listening to Dr Demento.