Working with Topo surfaces in Revit can sometimes be a bit challenging. I have created a sample file “Topo” available on the left, which will help show you how to manipulate topo surfaces. There are before and after examples of several situations. You will be able to see the final example and then be allowed to try creating it on your own.
1. Retaining Walls – Typically I try and hide all the contours within the wall itself. This is achieved by placing point directly aligned with one another and on opposite faces of the wall. Throughout these examples it is very important to keep point aligned with one another. If they are not aligned properly you will most often get undesirable results.
2. Swales – When creating swales or drainage ditches I typically find it easiest to keep my points aligned with one another (Grid layout is best) and just raise and lower the points to create the swale. Sometimes the misconception is to start out with a known contour elevation and place lots of points along a path to create the contour. This typically turns out to be more of a headache when modifying contours later. My advice is to stick with grid layout and align the points as much as possible.
3. Foundations – For creating a foundation I recommend using the building pad tool. When using the building pad tool it will automatically cut out the topo surface. Afterwards you can place a few points to grade the surface around the foundation walls.
4. Sidewalks – Sidewalks can be created in one of two ways. I prefer actually modeling the sidewalks in. The other is sub regions which will get covered later. The example provided shows that with a few simple points the topo surface can be modified to align with the sidewalk. When modeling in the sidewalks, it’s always a good idea to try and keep the grades just slightly below the top of the concrete. If you align the grade perfectly with the surface it becomes unclear which surface will actually show. Sometimes this grass will show, others the concrete and sometimes both. So avoid making them perfectly level.
5. Split regions – When modifying existing grades the topo surface is constantly trying to interpolate between points. In some cases (ie, property lines) you do not want to modify the grades beyond that point. This is ideally when the split region comes into play. If you split the topo surface right on the property line, any changes you make to the topo surface will not affect anything else beyond that point.
6. Subregion – The final example is subregions. With subregions you can split the topo surface into different areas and apply different materials to each area. Some examples might be; grass, water, earth, concrete, asphalt, etc.. You can also grade the topo surface however you wish and still maintain an uneven grade. Parking lots and sidewalks can easily be created with subregions.
