MODELING FROM A POINT CLOUD ON REVIT:
How do I contact a laser survey provider to obtain an optimized point cloud for revit modeling?
A quick reminder to start: what is a point cloud ?
A quick reminder to start: what is a point cloud ?
A point cloud (in geometry) is a 3D digital representation. It is a set of points, each located in a system of x, y, z coordinates.
A point cloud is created by a technician equipped with a laser scanning station. This one will take the measurements of thousands of points in space and assemble them into a coherent object
From point cloud to BIM mockup
To be exploitable in a BIM construction project, a point cloud in its current state is not sufficient because it contains only geometry and no intelligence (are there walls, doors?). The point cloud must therefore be treated as a BIM model. That is to say (re)modeled on a BIM tool.
Once recaptured by a BIM modeler in a BIM model, we can extract information relevant to the project: volume of concrete to be demolished, etc
Facilitate the re-search work with an appropriate point cloud
To perform this reseizure on a BIM software (such as Revit for example) it is necessary to have a point cloud processed for this purpose. For example, if the cloud is too large (several hundred GB), too extended or poorly geolocated: the modeling will be tedious, the tools slowed down, or even crash.
It is therefore necessary to be able to express your requirements to the laser scan provider correctly:
ORDER A POINT CLOUD FROM A SERVICE PROVIDER
TERMS TO KNOW TO COMMUNICATE WITH YOUR PROVIDER !
Format
If you work with REVIT you will need a *.rcp format (which is a ReCap format, if you have the AEC suite then you have a license for ReCap Pro and you will be able to open this format directly in its software to view the point cloud)
Decimated Cloud
Decimating a point cloud means removing redundant points, eliminating duplicates. Indeed, during the survey, some points will overlap, especially in the overlapping areas when the station is moved
from one point to another in the room. Decimating these duplicate points allows
to reduce the file size (up to 30% of the weight!) without losing accuracy. It is up to your service provider to perform this operation, which requires a point cloud
software and very powerful machines. It is always useful to
useful to specify in your specifications that your deliverable must be a "decimated
a "decimated" point cloud.
Georeferenced Cloud
There are several methods to georeference a point cloud, if you are working on revit we recommend working with a UCS.
Cleaned Cloud
Cleaning a cloud means removing objects of no interest from the survey (passers-by, furniture) as well as artifacts: reflections from windows or reflective surfaces. It is therefore a human intervention that cannot be automated. It is done in a tool dedicated to point cloud processing (ReCap, ...). You can either require a cleaned cloud from your provider (who will invoice you for the necessary man time), or do it yourself if you have ReCap licenses (included in the AEC Bundle).
Segmented Cloud
This is the cutting of the file into several pieces. Ideal for working on large buildings, it will then be possible in Revit to hide pieces of the cloud to focus on the areas to be drawn and thus make the work on Revit smoother. This is especially useful if you are modeling on low performance machines.
Sampled Cloud
It is a treatment that will define the density of points in the cloud: concretely it is a question of defining a number of points per millimeter. For example, sampling at 2mm means keeping one point every 2mm and deleting the other points. It is important to define a step that is compatible with the precision we are looking for. As a reminder, a laser scan has a precision of +/-2mm, which means that the difference can be up to 4mm with the real object.
