Sectioning point clouds

    
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Deri

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Registered: 2005-10-29

Message 1 of 3

 Sectioning point clouds
12-03-2007 11:44 . am   |   View his/her posts only
Hi folks
I've been asked to produce a series of 2D line drawings from some point clouds that we captured for a customer (essentially a large room with lots of pipework and structural steelwork). The point data is pretty rough (due to a lot of variety in reflectivity and feedback from oil/water in the atmosphere), which means that it's pretty much impossible to mesh up. My current method of working is to take thin sections through the point cloud in Navisworks and export these as bitmap images (no vector output!) which I then trace over. This is a PIA as you can imagine.
VX has been brilliant at importing the scan data sets - eating them up and reducing the point density - normally the meshing is pretty robust as well, but these scan files are two noisy for it. I got round to wondering as to whether you could use VX to create the sections through the point clouds in the same fashion as Navisworks, but have a far more acurate method of drawing in lines and splines on the section, snapping to point data.
A quick test shows that by using a combination of copying planes so they are offset by X distance (5mm in this case, but variable depending on point density / size of object), splitting the cloud using the planar split on both of these planes (result is a thin slice through the cloud) and then inserting a sketch on one of the planes and referencing points in the thin sliver of point could work.
Doing this operation manually for each section is a pain and VERY time consuming (more so than the export/vectorise route). Is there any reason why it wouldn't be possible to integrate several of these steps to have a "create point cloud section" command that resulted in a sketch on a plane with referenced points - it doesn't need to be clever enough to put lines and arcs through the resulting points (it'd be nice if it could though!!). Ideally this would allow you to work in a similar fashion to the "dynamic section" command for surfaces, but even if you had to set up your section centreline planes first and then apply the tool, it would be a great time saver.
My feeling would be that this would be a powerful tool for dealing with several point cloud scenarios:
1. Customer wants simple 2D sections from a cloud for estimating, discussing the shape etc - it'd be a lot simpler to bang an approximate section through the cloud without going to the hassle of meshing and surfacing.
2. Dealing with noisy data / incomplete data: If your data is too noisy to mesh, it would allow you to create a series of sections on a variety of planes and use these curves to loft a new surface to approximate the point cloud - the tools for comparing the new surface with the cloud are already there. You'd have a lot of control over how it dealt with continuity between lumps of scan data.

VX continues to impress with the way its engine deals with point clouds and the meshing engine is very powerful - it loaded up a set of point files that totalled some 1.2Gb of ASCII point data, reduced it down and span it round with no problems.
Any reason as to why this wouldn't be possible or suggestions on speeding up the production of sections?
Cheers
Deri
PS: It's just loaded up a single 870Mb point file as I've typed this and is processing a second one - I might have a 8 bedroomed mansion house loaded up at this rate - see attached.

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ChrisWard2k2

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Registered: 2011-11-22

Message 2 of 3

12-03-2007 04:08 . pm   |   View his/her posts only
Hi Deri

I expect I can help you to define a (crude) Design Automation program to do the preparation. I will need a sample file, if you email me I can give you my ftp details.

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Kyonghun

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Registered: 2002-8-28

Message 3 of 3

15-03-2007 09:40 . am   |   View his/her posts only
Hey, I just checked with the guy who does this at VX and he thinks it will be pretty useful, too.
See also
X