CloudCompare forum

What is the difference between 2.5D from 3D? What is happening to a 3D point cloud that makes it 2.5D?

2.5D means that there's no point that projects on top of other points when the cloud is projected along a specific dimension (generally Z). This generally means that the cloud has been acquired from a quite far distance without changing the orientation too much (e.g. with airborne LIDAR). Or that the shape has only one side (e.g. a mountain seen from the top, etc.).

In this case it's possible to project the cloud along this dimension (e.g. Z) without losing information. This is a requirement for all processes based on rasterization.

Thank you for your answer Daniel!
Would you reccomend using the tool "Compute 2.5 Volume" on a 3d cloud?

Not really! This could give some strange results (you would probably have to split the 3D cloud into two parts at least (like hemispheres of a sphere) to avoid confusion.