MEsh formation in Cloud Compare

[Gayathri_S]

Hi all

I am new to 3d data analysis and for using cloud compare application. I need to calculate the volume of the object from the point cloud data in .pcd format.
The 3d cam data was taken from one view and I selected an approach for forming mesh from the point cloud data. I am currently using Delaunary 2.5d(xy plane) mesh forming algorithm. When i try to calculate the volume for the mesh generated, getting warning like mesh has some holes and the volume got is also not matching with the actual volume.

Also want to do convex hull and concave hull for the mesh created in cloud compare.

Thanks in advance!

[daniel]

Sorry for the delay.

Well, it doesn't look to be simple (at least not with CloudCompare). You indeed either need a closed mesh (you can try your luck with the Poisson Reconstruction plugin, but I wouldn't expect too much of it with so few points). Or you can use the 2.5D Volume calculation tool (see https://www.cloudcompare.org/doc/wiki/i ... .5D_Volume), working directly with the cloud.

[DA523]

Convex hull (meshing) is super easy in Meshlab
Concave hull (meshing ) is super tricky in all software

[Gayathri_S]

Sorry for the delay.

Well, it doesn't look to be simple (at least not with CloudCompare). You indeed either need a closed mesh (you can try your luck with the Poisson Reconstruction plugin, but I wouldn't expect too much of it with so few points). Or you can use the 2.5D Volume calculation tool (see https://www.cloudcompare.org/doc/wiki/i ... .5D_Volume), working directly with the cloud.

Will it be possible for you explain what is happening in 2.5D volume calculation in cloud compare. My assumption is we need to give ground cloud data and object cloud data. The empty cell region in the occlusion region should be handled either by averaginf or by interpolation. Projecting in Z
(height) direction is used to calculate the height of the particular cell.

[Gayathri_S]

Hi

I am attaching the point cloud data for which i need to calculate volume. I have tried forming mesh for the data along with ground cloud merged with the object ground data. The mesh formed resulted in gaps. The volume computation is inaccurate.

Since the forum doesnt support upload of .pcd and .obj data am attaching the screenshot of those file. The aim is to create closed mesh with the given point cloud data and should calculate the volume for the mesh.

Thanks

[DA523]

Forum accepts attaching zip file less than 2 mb
You can zip just pc not mesh

[Gayathri_S]

Hi

I am attanching the cloud point for the above mentioned case. My interest is to calculate volume. So forming mesh is the first step. Need to form the closed mesh without convex hull method in order to approximate closely to the real volume value.

[DA523]

If this is your actual shape
1- Your 3 pointscloud is dense so 2.5d volume tools can find volume to ground (must segment each one)
2- Meshing is possible by CC but processing in BLENDER (extrude to almost ground .. etc)

.

mesh.png (76.5 KiB) Viewed 7463 times

SO

============= CYLINDER 2.5d volume ================

Volume: -0.026
Surface: 0.053
----------------------
Added volume: (+)0.000
Removed volume: (-)0.026
----------------------
Matching cells: 28.5%
Non-matching cells:
ground = 0.0%
ceil = 71.5%
Average neighbors per cell: 7.5 / 8.0

============= PISTON 2.5d volume =============
Volume: -0.033
Surface: 0.051
----------------------
Added volume: (+)0.000
Removed volume: (-)0.033
----------------------
Matching cells: 27.9%
Non-matching cells:
ground = 0.0%
ceil = 72.1%
Average neighbors per cell: 7.8 / 8.0

====================================
Edit ---> Mesh ---> Measure Volume
[21:49:39] [Mesh Volume] Mesh 'piston': V=0.0326455 (cube units)
[21:49:52] [Mesh Volume] Mesh 'cylinder': V=0.0244805 (cube units)

find atatched bin file in 7z file (archive)
..

[DA523]

cylinder.png (18.91 KiB) Viewed 7461 times

..
..

piston.png (36.88 KiB) Viewed 7461 times

..
For Convex Hull
use MESHLAB software
Filters ---> Remeshing --> convex hull