1. Description

Computes the difference (change) between two point cloud files.

2. Prerequisites

2 Point cloud files, almost perfectly co-registered. 

3. Workflow

3.1 Step by step to launch the analytics

Step 1 - In the "Analytics" tab, search and select "Point cloud difference" and click on "LAUNCH".

Step 2 - Select the "Reference Point Cloud" and the "Candidate Point Cloud". Click on "NEXT STEP".

Step 3 - OPTIONAL - If necessary, define the crop box on which you want to detect changes. To do so, you can use red, blue and green arrows to select the interesting part of your PCL. 

If you want to calculate the deformation on the whole PCLs, you can click on "NEXT STEP" directly. 

Step 4 - OPTIONAL - In case the 2 PCL are not perfectly co-registered, you can define 6 control points on each PCL to force the algorithm to align these 6 control points, and calculate deformation on other points with this reference. If you want to let the algorithm aligning the two PCL automatically, click on "LAUNCH POINT CLOUD DIFFERENCE" button directly.  

As indicated in the "help" pop up, you can either tag the 6 points on one PCL and then on the second one, or tag point per point on the two PCLs at the same time. What's important is to tag points in the same order, otherwise results will be false. 

To move points, just click on the red cross and move it with the mouse. 

Once done, click on "LAUNCH POINT CLOUD DIFFERENCE". 

Step 5 - Click on "FINISH" to come back to the analytics menu. 

3.2 Status and Progression

Check in the "LAUNCHED" tab that the analytics is in progress.

Aether will notifiy‍ the user when the analytics results are available.

3.3 Results

Once the analytic completed, a new "Difference PCL" layer is created. To visualize it, the user shall open the 3D viewer. This PCL is automatically displayed with the material "Normalyzed difference" selected, with a colour ramp varying from blue (few changes) to red (big changes). 

The user can play with the colour ramp to highlight the changes. 

4. Export Capabilities

The analytics result files are located in the‍ "Download‍" section. The user can download the generated PCL by clicking on the button "Download" at the end of the line.