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Dieter @ DWorks

DTM cutout ground

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Hi,

You can dig a certain height off the terrain with a dtm object, but this digs off the height over the whole shape. What I really want is to digg off the terrain to have a horizontal shape at the bottom and not a shape that follows the terrain. How can I do this?

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Can you post a graphic? Not understanding your need...

Can't post a pic now, but I'll try explain it in another way.

I have a sloped terrain that goes from 100m to 50m from one side to the other.

If you use a dtm object to dig something out, the bottom of the pit will be the same as the slope of the terrain. So the dtm object is digging for example 30m deep from the top of the terrein everywhere. What I want to do is dig out the terrein to a certain level so I can build from there. So the bottom of the pit needs to be horizontal.

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DWorks, Use a Pad (site modifier) set to zero slope. You can set the elevation of the pad to any (reasonable) number. Make sure the Pad is entirely surrounded by a Boundary. Make sure the Boundary doesn't touch or overlap the Pad, but the closer the Boundary is to the Pad, the steeper the cut of the terrain.

My favorite way to create Site Modifiers is by drawing polygons to describe them in top/plan then using Modify>Convert>Objects from Poly.

Site Modeling takes a lot of time and patience to get the hang of, but once you do it's a fairly marvelous thing (albeit not perfect and always improving).

Hopefully that'll help.

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I agree with you Peter - comverting existing objects to create modifiers is a very efficient way of working and allows you to design first and then work out what modifiers you need for the site afterwards.

I also agree that Site Modeling is worth the effort! Once you've mastered it, it should be the first thing you do with any survey - create a model of the site so you can really understand it before starting your design.

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DWorks, Use a Pad (site modifier) set to zero slope. You can set the elevation of the pad to any (reasonable) number. Make sure the Pad is entirely surrounded by a Boundary. Make sure the Boundary doesn't touch or overlap the Pad, but the closer the Boundary is to the Pad, the steeper the cut of the terrain.

My favorite way to create Site Modifiers is by drawing polygons to describe them in top/plan then using Modify>Convert>Objects from Poly.

Site Modeling takes a lot of time and patience to get the hang of, but once you do it's a fairly marvelous thing (albeit not perfect and always improving).

Hopefully that'll help.

Ok, I can use a pad with a boundary around it, and that works, if the boundary is the only one. I have a house wich has a pad to level the terrain and a boundary around it for 3m from each side of the building. The thing I want to cut out is a fountain that starts from the house and goes about 6m long and 1m wide. And because it is in the boundary of the house a bit, it's not working to just cut it out from the site model. I also found out that I can use the road tool and set the road itselfs into a class that I put out. But this road will also look at all boundaries. Is there a way to tell objects to only look at a certain boundary?

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You can have multiple boundaries - as long as they don't overlap. If they DO overlap, just turn them into one boundary (by using Modify>Add Surface).

For roads, I would not recommend creating separate boundaries for each road segment. Instead, draw your own boundary to enclose the modifiers you need.

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Interesting. I have usually found that using one, carefully thought out, boundary seems to work best for me.

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Yes that certainly works, but if you had modifications around the building and then had a new terrace several acres away from the building, you may want to put these into separate boundaries - so that you don't have to re-grade all the acres in between to accommodate both sets of changes. Could be costly!

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You can have multiple boundaries - as long as they don't overlap. If they DO overlap, just turn them into one boundary (by using Modify>Add Surface).

For roads, I would not recommend creating separate boundaries for each road segment. Instead, draw your own boundary to enclose the modifiers you need.

But the thing is that the water element may not modify anything in the boundary for my building, so how do you do that? because the water element starts from the wall of the building. The water element is just kind of a block that needs to be cutout from the dtm model.

Edited by DWorks

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DWorks, at this point it would be really helpful to see a visual. Can you take a quick screen capture of the plan and post it?

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Sorry DWorks, afaik you can't cut caves or back slopes out of the DTM.

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Thanks for the visual. If I understand your need, you can do it by 1) create a rectangular Pad for the water/pool, set it to be as deep as needed, make sure that the Boundary is VERY close to the Pad but not actually touching it (this will give you a nearly vertical cut). Then you will need to alter the building Pad that will now overlap the water Pad. Adjust it so that it is almost touching the water Pad but goes around it. Then update the Site Model... If I had the file I could probably do it fairly quickly...

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There I go, not reading the visual properly.

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If I had the file I could probably do it fairly quickly...

DTM problem vwx file

Here it is. I tried your solution, but it didn't work. You don't need to do it quickly. I already finished the building application without it, I just want to know a solution for future projects or for the implementation.

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