Article by Aric Stott of Trimble MEP
A lot of factors dictate creating a 3D CAD Model from a Point Cloud, such as detail level, scanning equipment, point cloud registration software, CAD software and more. Below is a light overview to cover most cases:
3D Laser Scanners typically create a point cloud that can be used to create a 3D CAD model, but not the CAD model directly. For the following example, a Trimble Scanner was used to scan a facility with the intent of creating a 3D CAD model, the main focus being on the walls, ceiling and structure.
Example: How to Create a 3D CAD Model from a Laser Scanner
The first step is to make a site visit and start scanning. By setting the scanner up in a set of targeted locations, you will be able to collect the necessary number of points for the detail level you are after. For many such situations, spherical and checkerboard targets will need to be placed to help registration software “stich” the multiple scans together.
Here is a floor plan shot of the building with scan stations visible to give a clear view of the layout.
With the scans complete, the site visit is done it it is time to start registering scans back at the office.
There are several point cloud registration software options out there. We recommend Trimble RealWorks for the flexibility it affords. The registration process is simple with RealWorks.
- Launch the software
- Import the files from the scanner
The size of each scan and the horsepower of your computer will determine how long this takes, usually a few minutes each.
Here is a picture of the registered point cloud.
With a registered point cloud, you can use RealWorks to make your task more manageable.
Transfering the entire cloud into your 3D modeling software, in most cases, is not possible due to the sheer size of the file.
RealWorks can be used to segment the cloud into more managable pieces which are easier for the CAD modeling software to digest.
These images are from RealWorks using the “Cutting Plane” tool.
This tool can be used to generate cut sections on all X, Y and Z axes.
With specific sections cut out of the model, they can be imported into the 3D modeling software to start creating walls, doors, windows, structure, etc.
Modeling time can vary greatly on how much or how little detail you are trying to get out of the scan.
The advantage of having the cut sections from a registered point cloud is that you have a template to follow.
Easier items can be done first (walls, floor, ceiling, etc.) then the structural system.
In the following example, the trusses were modeled once and then copy/pasted.
Here is the completed model.
Once the bulk of the walls and structure were complete, cut sections and a ceiling plan were able to be created.
This example is simply a general overview, however, illustrates the small amount of time spent compared to traditional methods for collecting as-built data to model from.
Furthermore, this example only required one site visit with a laser scanner.
|Approximate Building Size||30,000 Square Feet|
|Scan Time (Including Setup)||1 Hour|
|Registration, Segmenting & Sectioning||45 Minutes|
|Total Time Investment||Just Under 30 Hours|