GHS from point cloud

[Bengkeek]

Hi All,
What we are trying to do is from a laser scan of a hull generate a mesh that is then imported into Rhino were we can attach GHS to generate hull sections to calculate stability. The issues I have run into are GHS is not generating accurate sections of the mesh. We have done this successfully in the past but this is our first time doing the scanning and meshing in house.
the scanner we use is a faro focus
we have tried meshing in both faro scene and meshlab.

any suggestions would be greatly apricated

 

[Alan Cattelliot]

Hi Bengkeek,

If you have done this successfully in the past, what are the differences with your current processing flow ? Meshlab is the most capable for points clouds meshing and cleaning. Faro software can be also of some help, but it lacks some functionnalities, and needs a third party software and an additionnal post-processing step. Have you done any noise removal after meshing ? If the GHS sections are not accurate, do you have vertices on your final mesh ?

 

[Bengkeek]

Hi Alan,
Thanks for your response,
I have done hole filling using convex hull in blender and some smoothing of dark surfaces where the laser was less accurate and run several filters within mesh lab.
I have also done some pretty significant cleaning of the point cloud in scene before the meshing step.
can you explain what you mean by vertices on the final mesh?
it is my understanding that all meshes would be comprised of vertices

 

[Alan Cattelliot]

can you explain what you mean by vertices on the final mesh?
it is my understanding that all meshes would be comprised of vertices

Sorry, I wasn't explicit enough. For sections to be calculated by GSH, the mesh that is being imported into Rhino should have a lot of vertices, ie lot of points on which the mesh is defined. What is the vertices count of the mesh that you import in Rhino ? Do you have an image that illustrates the imprecision that you get in the GHS sections ? If you're using Blender, I suggest remeshing the result of the convexhull, before importing into Rhino.

Faro point cloud > Meshlab filtering + holes removal + denoising > Blender convexhull or shrink/Warp + remesh at higher vertices count > Rhino import

 

[Bengkeek]

Here are some photos with GHS attached and a photo of the mesh in blender.
the lines in purple are generated by GHS the red lines generated by Rhino
Rhino is able to generate nice sections however GHS is unable to generate clean lines along the hull

 

[Alan Cattelliot]

It seems that GHS juste skip somme points. What does the GHS offsets looks like ?
It maybe possible that points of the mesh are not rightfully ordered. Have you tried remeshing the surfaces un blender after applying the convexe Hull, with the option "delete un- used points" ?

 

[Bengkeek]

Its not quite working for us yet but the shrink wrap command seems very promising, it is generating a clean quad mesh without the noise we were seeing before, Thank you.
Rhino 8 will also have a shrink wrap and re-mesh capability

 

[darkstar71]

Here are some photos with GHS attached and a photo of the mesh in blender.
the lines in purple are generated by GHS the red lines generated by Rhino
Rhino is able to generate nice sections however GHS is unable to generate clean lines along the hull

If Rhino is able to generate nice sections, why don't you use the curves to construct your GHS model? Is there any further requirements?