Force Topo Boundary to follow specific shape

[Base12]

I'm attempting to model a building site which has a sloped, and curved driveway.  I'm trying to model the driveway as it's own toposurface (later I will add retaining walls, etc) and I don't know how to make the toposurface shape stick to the points I define (follow the yellow lines) without making it's own boundary (the areas with the red x's) which basically straight-line connect the end points of the shape.  What is the right way to do this?

[ToanDN]

Shouldn't you be modeling the topo larger and use subregions to define different areas?

[Base12]

I used .dwg topo lines to create the overall existing site - and I know how to make a sub-region that defines the driveway, but am unaware how to change the elevation points of [just] the sub-region?  Maybe I need to read up on Graded Regions?  I also know I can make a floor and modify the sub-elements to make it the shape/elevation I need, and then just put a building pad under the floor shape to cut out the terrain for that portion.  Just wondering what the proper approach would be - if there is one?

[barthbradley]

Sounds like you are grading the toposurface for a driveway.  I would do this by adding and removing points to the Toposurface - pretty much how it will be done in the field.   I would also do this with a Graded Region Copy in a forward Phase.  

Keep in mind that you'll need to add points to surface by RELATIVE elevation - not ABSOLUTE.  Relative zero is the actual surface of the Toposurface at the exact spot you are placing the Point.  

[Base12 · Accepted solution]

It looks like using a split surface and the pick-line tool for the shape of the driveway (which was in the .dwg topo lines inserted file) gave me what I needed.  I guess I just needed to write it out so see what it was I actually wanted!  Lol, always grateful for the feedback!

[barthbradley]

Split Surface?   HUH?  That ain't right. Maybe you're not doing what I thought you were doing.  

[ToanDN]

You change elevation of a topo or subregions using: adding points, modifying points, building pads.

[Base12]

I probably didn't explain it very well.  Here's what I got with split surface tho.

[barthbradley]

Yeah, that's wrong. Do what I told you.  

[mpukas]

Quite frankly, grading sloping, curved driveways in Revit is an archaic process. As the others have said, your method of using a split surface is not the correct/best method. I back-up the other's suggestions for creating a graded region and modifying points to create the shape and slope of the driveway. 

One method to consider is to create the driveway using a roof or floor, modify sub-elements to get the slope from start to end and inbetween, and then modify the toposolid by aligning point to the underside of the driveway element. One limitation is Revit cannot snap/align to a sloping curved surface. Archaic, but it can work. 

Another method, more common with Toposurface, is the grade the shape and slope of the driveway, split surface using the driveway outline, export to DWG, create mass using same DWG import, then create roof from mass. But with Toposolid, it seems Split Surface is no longer available. 

When Autodesk included and supported Site Designer, doing this type of grading was rather easy using Soft Terrain and Feature Line tools. Doing this type of grading by using detail lines to layout contours and then modifying points is infuriating, impractical, and virtually impossible. Autodesk needs to bring back and support Site Designer, or some other similar add-on. The example shown was done with 2020, the last year Site Designer was offered: 

[Base12]

Your solutions are probably fine for light grading and I will consider it on projects that aren't so steep.  This is a mountain property and we're holding back nearly 20 feet of grade with a series of retaining walls so the grade needs to step, not slope. It made the most sense (and was really quite easy in the end) to make a series of  split surfaces for the flat sections between the retaining walls (just edited those surfaces and set all the points, except for the ones on the ends, to the same level).  As noted previously I tried a floor at first for the driveway and adjusted the sub elements, but it was too choppy.  The split surface made it much smoother looking because it already had all the edge points along the curves.

[mpukas]

Ah, you're still using 2023 with Toposurface. In 2024 with Toposolid, split surface function is no longer available. You're method/solution looks good. 

I, too, work in the mountain communities and most of my projects have steep slopes. Grading driveways and site retaining walls without Site Designer is very difficult. I'm looking into Environment for Revit for better grading tools/solutions. 

[barthbradley]

Here's an early Christmas gift for you:

https://www.autodesk.com/autodesk-university/class/Make-Hardscape-Follow-Site-Topography-and-Site-To...

[Base12]

Well that's pretty awesome!  thanks @barthbradley !

[mpukas]

@barthbradley Thanks for the link. There are no doubt some amazing tips and tricks in Marcello's tutorial. He's genius and truly amazing what he can get Revit to do. I've learned some of these techniques, and I'll study this further. 

However, this tutorial does not address grading an existing topography where cut and fill are required. 

[barthbradley]

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@mpukas wrote:

However, this tutorial does not address grading an existing topography where cut and fill are required. 

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Grading with vertical cuts or grading like I'm showing in my screenshot above?  Vertical cuts can be made with Building Pads.  What I did above, is shape-edit the Graded Region Copy by strategically adding and removing Interior Points. 

Building Pad:  

 

[mpukas]

If the driveway/road is at 10%, how would you grade the cuts and fills at a 2:1 slope to meet existing grade? 

[barthbradley]

That question doesn't make sense to me. Care to elaborate?   

[Base12]

@mpukas, I think I get what you're saying.  Do you mean that instead of the fill between the retaining walls being flat, have it also slope (downhill I assume, not laterally) to the next wall?  That way you can minimize your wall heights.  Is that what you mean?  If so, I would start by grading the whole fill flat (except for the ends where it ties back to the undisturbed grade), then just pick all of the points on the downhill edge and reduce them all together by whatever the value would be.

[mpukas]

The driveway slopes up at a 10% grade from the intersection of the road to the garage slab. There are no retaining walls to support the cuts and fills. Cuts/fills are to be re-graded and have a max slope of 2:1 from the driveway cut to meet existing grade. 

To make it more complicated, there is a 2' shoulder on each side of the driveway that slopes downward from the edge of driveway at 3% grade. Cut/fill grade starts from the edge of shoulder. 

How would you grade this is Revit without any site grading tools?