Models of large structures are required for reasons such as restoration, documentation, and archaeological study. The possibilities to get a model of a building are: to measure every dimension or 3D scan the whole structure.
Normally it’s easier to scan a building rather than measure every part. In this article we will describe the process of 3D scanning a building.
The most common types of 3D scanning techniques are LIDAR and photogrammetry. The LIDAR process is mostly used in architecture and construction, its scanner has a high-powered laser moving horizontally and a mirror in rotation around a vertical axis. The laser scans thousands of dots every second. Laser scanning requires a high-end computer that can store and handle large amounts of data. The Photogrammetry produces 3D models from many pictures of the object of interest. The software 3D Zephyr is an example of photogrammetry software.
Some lasers are capable of scanning an area with a radius of up to 350 m (around 1150 ft) with one take. These laser systems can even be mounted on a drone to scan high rooftops or towers.
3D scanning can help restoration projects by capturing a lot of data about the building, and designers can better visualize their designs using the real-world building data as a foundation. Another point of interest is 3D Scanning archaeological sites can be useful for planning excavation or studying a structure that’s too fragile or dangerous to study in person.
Photogrammetry is more appreciated by hobbyists than LIDAR because it doesn’t require any technical training to use.
3D Zephyr is a photogrammetry tool that allows the creation of 3D models from 2D photos. You can try out the trial version of this software. Here is a guideline on how to use 3D Zephyr:
.The right weather – a cloudy day is best to avoid shadows. If you’re only planning on scanning one side of a building, however, this might not be a problem.
.Take pictures – Try to make sure the whole building is in every frame, and that they all overlap in the features they capture.
.If possible, use a drone to photograph the high parts of the building. 3D Zephyr has a great feature that allows the extraction of key photos from a single video, which will come in handy for this.
.Open the photogrammetry software. Click “Workflow” in the top left corner, and then “New Project”.
.If you’re willing to put some time into modeling, you can check the “Mask Images” box. You could skip this step.
.You need to import the footage. If the video is long, it will generate too many pictures, so try manipulating the “Similarity auto-discard threshold” option. Note that a higher value will produce fewer pictures from the same video.
.After importing pictures to the program you must adjust parameters for 3D model generation. Under “Category”, choose “Urban” (assuming you’re scanning a building or urban structure), and leave the presets as their default values. If Zephyr rejects some of the photos, use the “Deep” preset.
.Click “Run” and wait. Be aware that this process might take a while.
.The workflow menu, select “Dense Point Cloud Generation”. Leave the default parameters as they are and click Run.
.Repeat Dense Point Cloud Generation until you’re satisfied with the result.
.Next, under the Workflow menu, choose “Mesh Extraction”. If there are two or more different point clouds, choose the one you like. You can also experiment with presets before once again clicking Run.
.Before extracting the model, you could play with the tools for cleaning the model, such as scaling, rotating, and translating.
.When Textured Mesh is ready for exporting, simply select “Export Textured Mesh” from the Export menu. Choose the right format for your needs and select the destination folder, then export your final model.
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Source:
Darko Izgarevic, ALL3DP 3D Scanning Goes Big – 3D Building Scanner: How to 3D Scan a Building https://all3dp.com/2/3d-building-scanner-how-to-3d-scan-a-building/ published on Oct19 2019, published and re-edited by Rob Parker on Oct21 2019;
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