Forma update – 3D Buildings

Forma update – 3D Buildings

Have you seen the Buildings in Forma? Or in Infraworks? I often get asked how they are created and since there has been some changes, I thought I’d talk about them.

The data comes from Open Street Map (OSM) (https://www.openstreetmap.org/) a digital map that is built by a community of mappers all over the world. Because it is an open data source, managed by thousands, changes come fairly quickly, and the quality of information is really second to none. There is a framework, like most open source projects, that encourages innovation and you benefit from this innovation without forking out bucket loads of money.

OSM looks like this:

OpensStreetMap web page

Fairly standard maps you think. No! These maps are full of rich data. For example, let’s look at the building in the middle of this map The Victoria @ Media City. It’s not just a polygon, you have attribute data:

Office Building – Locality – Low emission zone – City Boundary – Public transport – Region Boundary – Low emission zone – Traditional – Statistical – State Boundary – Island – Country Boundary – Timezone –

The Victoria @ Mediacity MediaCityUK #1030140945 Salford Greater Manchester Greater Manchester Greater Manchester Clean Air Zone Lancashire North WestEngland England Great Britain United Kingdom UTC+OO:OO standard time

OpensStreetMap web page

The building is also split into multiple parts:

And each of these parts also have attributes:

Building levels Building material Building min_level Building part Roof levels Roof material Roof shape

5 Brick 2 yes 0 gravel flat

OpensStreetMap web page

The Open Geospatial Consortium (OGC) defines the Level of Detail (LOD) of buildings from LOD0 to LOD3 in the specifications for CityGML. Don’t we just love a TLA

OGC CityGML LOD

You may have come across LOD4 which described the inside of the building, but that was dropped as an addition to LOD0-3 was to add an attribute to state if it was inside or outside so this is now described in all LOD’s.

So, when you look at Google maps or Bing maps or indeed OSM, we initially look at LOD0, but we can do better, given all this information. Now, I am aware Google Maps do 3D Buildings and they are quite impressive. This uses a totally different technology that is not easily editable or useful in our software.

Google maps uses Photogrammetry. For you Recap Pro users, yes, that is the same tech that Recap Photo uses. Put simply, they fly around in planes, taking many high-resolution images at various angles and use computers to search out matching features and can calculate where each pixel is in 3D. They then make a Triangulated mesh and map the image onto it. This has advantages, and is very cool, but also has disadvantages, not least, the representation struggles with overhangs and can be quite ugly close up:

Google Maps

Also, if you wanted to edit it, you are editing a mesh and not a primitive. And I know you, you would much rather edit a simple primitive than a complex mesh!

Infraworks and Forma used the same source for their buildings in the UK and most of the rest of world. There are some exceptions in some places, but most of the time it’s OSM. But all they did was look for an attribute that stated the building height and extrude up the polygon to that height. If the attribute was not there, it set an arbitrary height.

Here is Infraworks on that building: Infraworks – OSM data

And here is last months Forma on that Building: Forma – OSM data

Now, go and look buildings a bit closer and try to establish what the height is. As in where on the building do we measure to? Here it is in Google. Which height do you use? There are so many of them.

Google Maps

The results in Infraworks and Forma are really poor for this type of complex building. However, if we split the building up into primitives, and give each primitive attributes we can get much closer to the real representation of the building.

Forma has done this. It is using the data far more intelligently. Whether it is getting the improved buildings from another provider, or whether Autodesk are doing the building themselves, I’m not sure at this stage, I’m going to assume the later as there is no additional recognition or copyright on the maps other than OSM.

Forma – OSM data comparison

The next stage is to move to LOD 2 and 3 and add the roof detail and the materials. So watch this space.

Remember, you can link this direct to Revit, so mass modelling existing buildings should be a think of the past. If you would like any more information on this topic or learn how to access Forma and work with Revit, please contact Graitec.

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Written by Ian Robinson – Software Technical Specialist