Point Clouds can be scaled outside of Reconstruct and imported into design software for further design work, and creation of as-built BIM models. In this example, we will use Cloud Compare (to scale the point cloud), Autodesk Recap (to convert the scaled point cloud) and Autodesk REVIT (to create BIM), but please note that these functions are not exclusive to these software's.
In Reconstruct
1. Measure the distance of a scaled/calibrated model, making sure to pick points in areas that are well sampled (with lots of points).
Hint: Pick points that are as far away from each other as possible. The longer the scaling dimension (relative to the overall point cloud size), the smaller the error in scaling is.
2. Go to the Data Manager, and the Point Clouds tab, select the Point Cloud and select Download. In the Download Menu, select the option to download the original Point Cloud. The point cloud is in .las format, and is usually unscaled when exported from Reconstruct.
In Cloud Compare
3. Open the Point Cloud.
4. Select the Point Picking Command.
5. In the Point Picking tool, select the “Select 2 points…” command.
6. Select the same two points as were selected in Reconstruct. The distance between the points will be shown in meters. This is the unscaled dimension.
7. Calculate a scaling factor with which to scale the point cloud using the formula below:
Scaling Factor = Field Verified or Desired Dimension/Unscaled Dimension
8. Select the point cloud in the DB Tree, and then in the Multiply/Scale command (Edit > Multiply/Scale) type the calculated value for the Scaling Factor in the Scale field.
9. Select the Point Cloud in the DB tree and Save it with a new name.
Note: This procedure should only be necessary for Point Clouds created from 360 Images in Reconstruct where no April Tags are used in the Capture. When April Tags are used, the Point Cloud should be automatically created true to scale in Reconstruct, obviating the need for scaling in Cloud Compare.
In Recap Pro
10. Create a Recap Pro Project, and select the now scaled Point Cloud for Import into Recap. In the Scan settings page, make sure to set the intensity clipping at 100%. This will import the entire point cloud as is without Recap filtering out any points. In Recap Pro, the point cloud can be aligned with a specific EPSG coordinate reference system. If your design model contains such coordinate system, then choose the appropriate coordinate system. If the design model is a local coordinate system, an extra step will be needed (see below).
11. Select Index Scans, and Launch Project.
12. If the design model is a local system, then go to Settings in Recap Pro, and reset the Origin to 0,0,0 and save the fie.
13. Once the point cloud loads, select Save As to save the Recap Project in a location of your choice (with the .rcp extension). You an also save the file as .rvt, if the point cloud is only to be used within Revit.
In Revit
14. Create a New Project (or open an existing project).
16. In the Insert > Point Cloud command, select the .rcp file (or .rvt file) saved from Recap.
17. If the point cloud and BIM do not show up aligned in Revit, then use zoom extend. Next, select the point cloud and move/rotate it to the right location and orientation against the design file.
The scaled point cloud from Reconstruct should now be imported into Revit for further use in creating as-built BIM models.
Comments
0 comments
Please sign in to leave a comment.