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File requirements

VU.CITY supports models in the FBX format (2011-2016).

If your modelling/CAD/BIM package is only able to export newer, unsupported versions of FBX, Autodesk provide an FBX converter here.

The maximum file size is 128MB, and the model should have all geometry joined/merged/collapsed into a single object.

FBX as a file format is well-suited to high-end rendering and gaming, but not commonly associated with CAD or BIM platforms. As a result, dedicated modelling applications work well with FBX, whereas many CAD and BIM platforms need additional steps to produce an FBX file suitable for rendering in applications like VU.CITY. Any considerations or workarounds we learn of that help produce suitable FBX files will be posted here.

Preparing your model

There are several concepts you’ll need to familiarise yourself with to help understand what makes a VU.CITY-ready FBX file.

The following video demonstrates zeroing a model using a dedicated 3D modelling package (Blender), and how the location of the model’s origin / pivot is used when positioning the model in VU.CITY:

Note this workflow will look different and the terminology will vary from app to app.


Zero is an abstract reference point at the centre of 3D space where X, Y and Z all equal 0.  In much the same way we consider Earth’s position relative to the sun, a model’s position is considered relative to zero.

Zero is also referred to as World Zero, Origin Point, 0,0, and 0,0,0 in different applications.

Modelling packages generally display a grid in the centre of the 3D scene, and zero can easily be found at the centre of this grid.

However, CAD and BIM packages often don’t display a grid in the centre of the 3D scene, and zero can be hidden/invisible.

VU.CITY uses zero in 3D space as a common reference point for zero in the grid coordinate system relative to your city (GBOS for UK cities, and ITM for Belfast). Therefore a model’s relative position to zero should be the same as your survey coordinate’s relative position to the origin of your grid coordinate system (this is illustrated further below).

Pivot / Origin

The pivot / origin of a model is used by VU.CITY to locate where your model is in 3D space. This is an important concept to understand when applying geolocation to an FBX file.

If for example your proposed site plan contains a survey coordinate, the location of that survey coordinate should be set as the pivot / origin of the model, and the position of the pivot / origin relative to zero should be the same relative distance specified in your survey coordinates.

So if your proposed site plan looks like this:

…the pivot / origin of your 3D model should be positioned here:

…and the position of your pivot / origin should be relative to zero like this:

CAD and BIM packages are mostly unsuitable for positioning FBX models in this way. Geolocation settings from CAD and BIM packages generally don’t translate into FBX files, and this is because we are pushing both the limits of what FBX was made for, and what CAD and BIM packages were designed to do.

If therefore you don’t have access to a dedicated 3D modelling package such as 3ds Max, Maya, or Blender, and you’re unable to set your origin and position the model relative to zero as described above, we offer a number of modelling services that can help you out.


VU.CITY supports mm, cm, m, in, and ft.

If you have geolocated your model inside your chosen modelling/CAD/BIM package, please note that your survey coordinates will need to be converted to the scale of your model. For example, if your model was built in millimetres, and your survey coordinate was E 531000, N 180500, then the position of your model inside your modelling/CAD/BIM should be 531,000,000mm east and 180,500,000mm north of zero.

If, however, your model is zeroed (i.e. not geolocated), when you manually enter your coordinates into VU.CITY, you must enter them in metres regardless of the scale of your model. This is because VU.CITY uses the default scale of the grid system (which for both OS and ITM is metres).

Dealing with scaling issues

Models imported using the incorrect scale may be too small to see, or be offset outside of the bounds of your city. To you, the outcome will look the same – your click the import button but don’t see your model.

The way you can tell if a model has imported or not when you cannot see it is to click the location pin icon that appears in the import menu:

If the model imported successfully, the camera will pan to the location the model should be.  If however the camera does not pan (you may need to pan to a different location in the map, then click the location pin again to verify) then the model has not successfully imported.

If you’re unable to see your model in VU.CITY, troubleshoot by re-importing using a different scale. If you cannot see the model regardless of the chosen scale, please zero your model then try again.


There is no theoretical limit to the number of vertices you can use as long as it fits into the 128MB size limit. This allows for highly detailed models, however, the way these models are optimised will determine whether or not they can be imported successfully.

If for example you save 100 files totaling 1GB to your computer, this will take longer and be more computationally demanding than saving a single 1GB file. When you apply this computing principle to a high-detailed model which is typically made up of thousands of objects / layers, you’ll find your model won’t import smoothly, and may not import at all on less-powerful hardware.

Please therefore merge/join/collapse all geometry into a single object before exporting it to FBX.