Octree's parameter filled volume

[Gracias25]

Hi! I am doing a master's degree and I have been using Cloudcompare but I got some questions I can't seem to find answers to. it is about octrees. So i compute de Poisson reconstruction, I get the mesh and octree. When I click on the octree I can see octree's parameters but they are some I can't explain. I was supposed to compute the volume of my pointcloud so I used filled volume in octree parameters. But when I change display level the filled volume changes. The higher the display level the lower the filled volume. So I'd like to understand what exactly the filled volume is. Thanks

thumbnail.png (37.34 KiB) Viewed 1965 times

[daniel]

So this is the 'volume' of the octree (= sum of the individual volume of each (square) cells in which points are present). The greater/deeper the octree level is, the smaller the cells are. Hence the total volume generally decreases.

Anyway, this is definitely not a reliable way to measure the volume represented by a point cloud.

If you have a 2.5D cloud, you should definitely take a look at the 'Tools > Volume > Compute 2.5D volume' tool (https://www.cloudcompare.org/doc/wiki/i ... .5D_Volume).

Otherwise, you can try to compute a closed mesh (with the Poisson Surface Reconstruction plugin typically - and 'Dirichlet' boundaries) so as to obtain a closed mesh. You can then ask CC to compute the volume of the mesh (but it needs to be good AND closed).

[Gracias25]

Thank you for the quick answer. I tried the Poisson reconstruction with "Dirichlet" parameter and also asked CC to compute mesh volume. But I couldn't find out what the Unit was? Could you help me with that? Thanks

[daniel]

CloudCompare doesn't manage units. It simply load the coordinates as they are stored in the input file. Either you know what the units are, or you can try to guess with the scale bar or the point picking tool. Then all the measurements will be displayed in the same units as the point coordinates.

[Gracias25]

Hi! I've got a question about CC Mesh compute volume. I am doing a master's degree and using CC. I'd like to know if possible the algorithm that is executed in the background. Is there any article that describes that ?

Thanks

[daniel]

See "EFFICIENT FEATURE EXTRACTION FOR 2D/3D OBJECTS IN MESH REPRESENTATION" by Cha Zhang and Tsuhan Chen (2001)

[Gracias25]

Hi! I have a question about the mesh volume calculation:
Edit > Mesh > Measure Volume

How do we do this in command line ? I can't seem to find it here : https://www.cloudcompare.org/doc/wiki/i ... _line_mode
And save the result in an Excel file possibly

Thanks

[daniel]

Hi,

his function has not been ported to the command line mode yet.