In June of this year (2011) we at eBIM were commissioned to fully laser scan and produce a Revit model of the Monument Mall shopping centre in Newcastle upon Tyne.

Up to this point we had produced Revit models from laser scan information, but Revit versions up to and including the 2011 release had no native method of inserting scan information directly into the Revit workspace, therefore much of the modelling was undertaken by in a long winded fashion – tracing from scales images and calling off dimensions from pointcloud viewing software.

However, the 2012 release of Revit was built to incorporate pointcloud insertion, which naturally appealed to us – constantly searching for the most efficient and accurate ways to convert our scan data into deliverable BIM. Once we were given the go-ahead by the project team, we proceeded to model the building using r2012 and its pointloud insertion capability. This is what we found.

Monument Mall – pointcloud visible (in red)

Pinpoint Accuracy
By far the greatest advantage of being able to directly insert the pointcloud information into Revit is that of the accuracy of the information you are drawing from. Effectively having every single as-surveyed laser ‘dot’ transferred directly from the face of the building into the Revit workspace means the modeller can accurately transpose the faces of all surveyed features and draw their system families, in place models etc to suit. The process of this also effectively eliminates the ‘chinese whispers’ effect that comes with transferring information from a pointcloud, via another piece of software or output (say, a scaled image which can be blurred or poorly positioned) before it reaches the Revit workspace.

Another positive effect this can bring is the speed at which a model can potentially be built, with the ‘tracing surface’ provided by the point cloud being available to draw over in three dimensions, precisely relative to all other elements of data in the entire surveyed cloud – the cloud itself lending itself perfectly to the practice of 3D viewing and working.

Pointcloud, this time in blue.

Teething problems…
Naturally, with both the practice and the software being relatively new there were a number of, shall we say, teething problems – some which were software based and some which were experienced based. With most cases, the scan itself is not able to be imported into the Revit workspace from its raw data and requires ‘indexing’ into a Revit friendly .pcg file before it can be used.

Although not laborious, the indexing takes time in itself and can sometimes be prone to failing if the workstation is overloaded. Once indexed we encountered some difficulties in positioning separate .pcg’s so that they lined up with each other – with the .pcg’s having to be positioned manually upon first appearing in an obviously wrong location. However, our contact at Autodesk assured us that this was a software gitch, and sure enough upon updating Revit the .pcg file more often than not lined up with perfect relation to those previously inserted.

The biggest difficultly presented with point data in the Revit workspace comes with navigating and viewing the data – the current Revit set-up struggles to handle the large graphical capacity that a collection of millions of individual points demands making orbiting, panning and zooming slow and/or jerky. Combine this with the constraint that Revit will only display a limited number of points on screen at any given time (regardless of how close or far away from the data you are) and viewing can become a little strenuous on the eyes over a long period of time, notwithstanding slowing down the fluidity of your modelling. Again, this problem has already been noted by Autodesk and we are assured the graphics are being overhauled to cope with this new demand – the fruits of which are likely for the next full release of Revit.

Conclusions
By looking at the list of pros in comparison to the list of cons you may be mistaken to think that the integration is more problematic than it’s worth at present, but in truth although the cons are numerous they are small and massively outweighed by the pros. And in reality, the most major cons (in my opinion the slow graphics issues and insertion position problems) will be a thing of the past come the next full release of Revit, leaving only the only effectiveness and efficiency of the individual modeler sitting behind any given desk as a barrier to the precise accuracy and quick turnaround. A combination of well scanned and registered data, with an intuitive and able modeler (or well organised team of modelers) can already produce a high quality BIM ready for use for Architects, Engineers and the like – and with the basic improvements on the horizon the process can only get quicker.