convert mesh to point cloud

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bab
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convert mesh to point cloud

bab
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hy!

i found this nice tool in to generate partial view of a mesh.
http://www.pointclouds.org/blog/gsoc/aaldoma/index.php

Does anyone know how the a mesh is converted to a point cloud?
Maybe raytracing?
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Re: convert mesh to point cloud

VictorLamoine
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Hello,

In fact there is no real conversion.

A mesh is a point cloud with faces connecting the different vertices (= points).
We talk about points in a point cloud and vertex/vertices in a mesh but they are exactly the same.
Faces are usually triangles but other faces types exists (they are far less common).

Be careful; a TopSolid, SolidWorks, AutoCAD... component is NOT a mesh, each software has it's own way of describing the shapes etc. if you want a point cloud of a CAD you have to export in OBJ, STL, PLY format and delete the faces.

For example this is a very simple mesh in PLY format: (in this example, the face joins 4 vertices)
ply
format ascii 1.0
comment Mesh example
element vertex 4
property float x
property float y
property float z
element face 1
property list uchar uint vertex_indices
end_header
-1.000000 -1.000000 0.000000
1.000000 -1.000000 0.00000000
1.000000 1.000000 0.000000
-1.000000 1.000000 0.000000
4 0 1 2 3
If you remove the face you have a point cloud:
ply
format ascii 1.0
comment Mesh example
element vertex 4
property float x
property float y
property float z
element face 0
property list uchar uint vertex_indices
end_header
-1.000000 -1.000000 0.000000
1.000000 -1.000000 0.000000
1.000000 1.000000 0.000000
-1.000000 1.000000 0.000000
Save these two files as PLY files and try to open them with MeshLab

Bye
bab
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Re: convert mesh to point cloud

bab
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Ok that sounds clear for me. But the sampling procedure which is provided for example by
the "plc_recognition_framework" returns dense and also uniform! point cloud. That means the
triangles are somehow filled? Only the vertices of the meshes would result in a point clouds but which
is not uniformly sampled.

I am wondering how the "faces" are filled...