calculate vertical obstruction

[leo]

Hi! it's been a while since my last post.. I am bumping my head on a new information I would like to extract from the whole point cloud/mesh. Sometimes the area of interest (in my case a vertical escarpment of natural origin) has some overhanging areas. These zones cast a "rain shadow" under their vertical column. I would love to highlight and use this information and calculate the surface of the areas that are covered under them. So..might it be possible that some workaround of cloudcompare could calculate the vertical obstruction created by some areas? I think the key is playing with the Z information? Similar situations might be of interest in engineering (for example areas under bridges) or in architecture in general. A similar topic might be the the viewshed analysis in 3d models, in this case with an ehnanced Z component. For single points i figure i can tell if they are obstructed in their verical component by looking at the cross section..Thanks!

[daniel]

Maybe you could use the 'PCV/SahdeVis' plugin?

This plugin is used to simulate the quantity of light that each point of a cloud receives, as if it was under a dome of light (and the points are occluding each others). That's the default behavior, but you can also use a secondary point cloud to specify the light directions (only its normals will be used). So you can simply create a plane entity on top of your cloud, with the normal pointing down, and then sample a few points on this plane. Then use the resulting cloud:

pcv_dialog.jpg (23.99 KiB) Viewed 1105 times

(you can probably use much less points/rays if there's only one direction, 10 would be sufficient)

And you'll get a scalar fields with the 'illuminance' of the points, that will let you select the points in the shadow of the others:

pcv_shadow.JPG (45.38 KiB) Viewed 1105 times

[leo]

Thank you very much Daniel, it works flawlessly!