What is a Point Cloud?
A point cloud is a digital representation of existing space in three dimensions. It is created by laser scanning existing buildings, spaces and structures, linking hundreds of thousands of such spatial coordinate ‘points’ together . The 3D map of points (often overlaid with a colour photographs) rendition of the points) and is then imported them into specialist software which can interface with our 3D building modelling systems.
Why do we use them?
The precision and accuracy of the point cloud mapping system ensures that it is an extremely useful tool to digitally represent existing conditions. It creates a “real world” depiction of what’s going on with our site, so there is no guess work or time consuming hand measure-ups needed. If we are designing a building that connects onto an existing one, we essentially have highly accurate existing drawings, but in 3D!
Point Clouds support our design by allowing us to design around an actual site setting, making us accurately detail and model existing buildings. This helps in Revit with things like phasing, cost planning, constructability, and detailing.
What Program do we use to work with Point Clouds?
Autodesk has created a Program called ReCap, which allows us to directly open a Point Data file and from that, create a Point Cloud File (.rcp).
In ReCap you can change the Display Settings of the point cloud by changing “Visual Noise”. This increases or decreases how many and the size of data points displayed, changing the visual appearance and the performance on the program.
Changing the colour style helps us visualize in different ways the different parts of the building in different ways. You can visualise change the between RGBColour, Elevation, Intensity, Normal and Scan Location.
The ReCap Limit Box
Revit users will understand the concept of the ‘Section Box’, which puts a cube-like 3D box around all of the modelled elements in any 3D view. The advantage of the section box is that it allows the user to move the sides of that box, and you can make it smaller and smaller, which essentially starts cropping the building elements. This is very useful if you are modelling an intricate part of the building and you want to cut through the building to have a better look at the element that you are working on. You can do the same thing in ReCap. The Point Cloud is often taken of a large site, so it takes time and effort to orbit around, trying to zoom in to a particular location. ReCap has a ‘Limit Box’ which does essentially the same thing, allowing us to strip the model back to let us get to the part we are working on.
Another useful tool in ReCap is red lines, which highlight the edges that are being cut. For example, if we were to cut directly through the building, for example, we would clearly be able to see the finished floor levels clearly, which would allow us to and from that we can take measurements.
How to use a Point Cloud in Revit
Once we have created a ReCap model (.rcp) from our data point file, we can save it in our project folder location so we can easily access it from Revit.
To load it in:
In Revit, go to the Insert Tab, hit the Point Cloud Button, and Select the ReCap file for your project. Step 4 is noted as optional: if your project has been set up with ‘Shared Co-ordinates’ then use that option; if not, then just select Auto – Origin to Origin, then select open.
Why is a Point Cloud useful in Revit?
As stated previously, it is a great help in identifying existing site elements. As an example, if the building company is unsure where the power lines are, and whether or not the crane can fit under them for the precast panel lift, we can provide very detailed drawings with the click of a button, pinpointing where the power pole and power lines are, as well as their sizes and heights, which we can then model that into our Revit model.
The other great thing about a Point Cloud is that whatever view is on the screen, the point cloud can always be referenced. That means that if I’m in a Plan, Elevation, 3D and Section, it will always give me a clear and cut detail about what is going on in that particular part of the building.
The 3D views cut using Section Boxes still cut through the Point Cloud, which is very useful for finding problems and clash detecting with existing components. It is not only useful for Architects and Builders, but also for Services contractors, as the level of detail a point cloud can provide is extremely accurate. Depicting where existing pipes and duct work are located could prove extremely useful.
With 3D Scanning becoming much more affordable, it is highly recommended to get a point cloud for a project containing existing buildings. The accuracy of a Point Cloud and subsequent model can save time with site visits and measure ups. This does not just aid the Modeller in the office but assists the contractors on site. They can easily find their set out points from what they can see on a tablet, rather than trying to locate items from 2D plans. Linked with on-site scanners, it will provide accurate setouts for off-site prefabrication and checking of construction installation, as well as as-constructed information for facility managers and owners.