Large .las files

Hi guys.

I am trying to explore Volvox for import of large pointclouds (>7gb) from 3D scan.

The file is .las and is more than 7 gb of size.

Is Volvox to open .E57 files only, meaning that the .las file needs to be converted first in CloudCompare?

I am having quite some problems opening this file in CloudCompare as it seems there is problems with the large file size.

Does anybody have a good best practice for this?

I am glad to explain more - if I can :)

Best regards Rasmus

Replies to This Discussion

Permalink Reply by Martin Tamke on April 1, 2016 at 3:51am

Hi Rasmus

LAS is a binary format similar to e57. so one cannot "simply read it" like ASCII formats and writing an importer takes quite an effort (ask mateusz :-) )

I dont see a way around converting the file either in cloudcompare or another tool into e57. This requires lot of RAM required - we have such computers here...

Processing 7GB will be a problem anyahow. so either you subsample massively and/or you just load a subset of scan positions (if it is a terrestrial laserscan and not a Aerial)

Volvox allows to inspect scan positions before importing and to import only a subset of these. this is handy for processing. One can make a handy batch routine, where a massibe Pointcloud is broken down into smaller chnunks and finally written out as one subsampled e57.

hope this helps - else come back here

martin

Permalink Reply by Rasmus Holst on April 1, 2016 at 5:29am

Hi Martin.

Thanks :)

I have subsampled the .las quite hard and exported as .e57.

The thing is that I do not know much about this scan (or any other scans for that matter), but it seems when using your example file about positions, the file has only one.

This might be because of the conversion i CloudCompare? Or maybe it is and areal scan. I will try to figure out more.

The idea is to make a cylinder brep and cull all points outside this right?

However I will now try to see how I can best work with this e57 in Volvox and maybe try to find some tutorials or example files. If you have any good examples of how to best convert this to mesh/geometry and if there is a good way of structure in order to get some geometry into a BIM environment - here Revit - please let me know :)

I think, making one or more subsets are probably a really good idea. Would you just import the points in GH with Volvox and then cull points outside some brep?

Thanks.

Permalink Reply by Martin Tamke on April 1, 2016 at 8:05am

Hi Rasmus

Cloudcompare gets indeed rid of all Cameraposition during an e57 conversion.... too bad.

Cropping is the right way. You could as well separate the pointcloud into building, terain, subterain structure etc. One can do nice freeform selections with meshes and the meshinclude component in volvox.

Revit has a pointcloud engine, which loads recap files. this allows for a hybrid display of your BIM geometry and Point Clouds.

making meshes for landscapes is realtively simple. automated ways to mesh the tunnels and buildings and streets etc from your example is another thing

Permalink Reply by Henrik Leander Evers on April 1, 2016 at 8:20am

Hi Rasmus

The loss of scan positions could be in the conversion in CloudCompare (if it is terrestrial scanning). On the other hand I believe .las file were developed for aerial LIDAR scanning and might not even support scanner position.

The idea with the cylindrical breps. What is it you say your idea with this is? To devide the cloud into several chunks?

First of all it will not work with cylindrical breps. It will work with cylindrical meshes. But this will be slower than using a brep box. So if it is to crop the cloud into chunks I would suggest boxcrop.

About the conversion into geometry for Revit there would be several methods. It first of all depends on which purpose this will have in Revit and the precision needed.

Besides this the strcture of your cloud has something to say about how I would go about to do this. it is a bit hard to see in the picture. If your point cloud is 2.5 D (an areal scanning) I would simply try to use the volvox delaunay mesh. If it is rooms of some kind ("floor, wall, ceilings") we could set up a script for these parts which could assist the modelling of surfaces on a best-fit plane through through that part of the point cloud, and then use delaunay on the context.

But again it really depends on what you are going use it for. You could also model the things absolutely needed as geometry in Revit and then prepare the point cloud to import it into Revit as reference and context.

Maybe you can send the subsampled version of your e57 over wetransfer (or somehow). And I can maybe better guide how I would go about this.

Permalink Reply by Rasmus Holst on April 4, 2016 at 4:03am

Hi Martin and Henrik.

Thanks for your tips.

I have now the point cloud in Rhino - by translation in CC. I will try to do the same, subsampling etc., through Volvox later as that seems even smarter.

Nevertheless I now have the point cloud - and at the moment I am not really aware what kind of geometry/output my colleague is looking for, but I will find out.

About the import into Revit, can the recap files .rcp or .rcs from e.g. a boxcrop etc. be produced through Volvox?

Thanks

Rasmus

Permalink Reply by Henrik Leander Evers on April 5, 2016 at 10:22am

Hi Rasmus

You should be able to export a E57 (and also a XYZ) file from Volvox, which can be read and converted in Recap into .rcp/.rcs files. These are then opened inRecap or imported into Revit.

Permalink Reply by ng5 Alex on April 1, 2016 at 12:21pm

Hello Rasmus,

you can also try and convert the las file to txt or xyz. Volovx handles really well txt files, though the max file size i have used is is 2.5gb.

best

alex

Permalink Reply by ng5 Alex on April 1, 2016 at 12:53pm

I did a quick test with a 4gb point cloud (output from sfm software, in xyz txt file).

load time was aprox 4-6 minutes. (some part of it for the gfx card to catch up). Memory stands at 9.5gb. A wild guess would be for 7gb would be something like 15min to load and twice the memory (?).

without subsampling editing with other volvox components is a bit on the patience side. But i have found through another project that volvox subsampling works really nice, without affecting the details of the geometry. (i was quantifying facade defects, without significant differences between subsamples).

best

alex

Permalink Reply by Rasmus Holst on April 4, 2016 at 4:06am

Hi Alex.

Thanks for your idea.

I haven't tried this translation into .xyz files, but for now conversion to e.57 worked really well :)

It does take some time, but turning off display in CloudCompare helps alot - I think next I will try to do the same with the CloudCompare engine from Volvox.

Not to find out what to do best with all of these points :)

Permalink Reply by Parimal Vala on July 4, 2019 at 12:19pm

Hello Rasmus,

Currently I am doing my master thesis on topic related to point clouds and Volvox.

I have .las point cloud file and exported that .las file to .e57 through Autodesk Recap. then through I tried to import that file. But its not working?

Could you please give me some ideas How can I cope up with it? If you could explain me the process How did you import? It would be great help

Thankyou

Permalink Reply by ng5 Alex on July 4, 2019 at 12:47pm

unless you have inverted the button states, load57 component is set to false thus nothing loads.

Permalink Reply by ng5 Alex on July 4, 2019 at 12:54pm

its pretty basic grasshopper

the loade57 component needs an ok to start loading, declared with a true to load, and false to not load. You are using a button which by default is false.

try using a boolean toggle instead, set the state to true and wait for the cloud to load.