Export XYZ fail

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Export XYZ fail

Postby kallek » Thu Jan 12, 2012 8:20 am

I want to export a POD file from Pointools EDIT 1.5 to XYZ coordinates to import in meshlab to create a mesh. The export itself runs smoothly but when done the actual *.xyz file is 0Kb. But it creates a bunch of other files like *.bk0, *.bk1 etc that includes some information (not readable). Have i done something wrong here? the other obvious question is, is this the right way to go? I also have a Leica cyclone file *.imp that is huge but i dont know how work with this kind of file.

Any suggestions?
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Re: Export XYZ fail

Postby blazaj » Thu Jan 12, 2012 8:37 am

Hi Karl,

try to export without the clipping planes active. I had similar issue with PT View Pro and this was the thing that caused it. If it is the case and you want to export just the clipped part to XYZ then first export clipped to POD and then the new POD to XYZ without clipping.

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Re: Export XYZ fail

Postby kallek » Thu Jan 12, 2012 3:38 pm

Thank you! I solved my problem. But now i have another problem instead... When i import the XYZ-file in meshlab it seems to load but shows up. Is there some parameters to click when exporting from Pointools, ex scale factor etc?

I also tried to export into *.PTS and that didnt work at all...
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Re: Export XYZ fail

Postby mike annear » Fri Jan 13, 2012 1:24 am

Hi Kallek,
.xyz files should go into Meshlab without any problems.
There is an icon for "points" (display as points) on the menu bar.
Cheers,
Mike.
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Re: Export XYZ fail

Postby kallek » Fri Jan 13, 2012 7:51 am

Sorry, my last post was not very explaning.

When exporting to xyz there are som other parameters beside teh XYZ-coordinates. RGB (0-255) and I for intensity (0-1, typical 0,03865 etc) is also included in each row. When i import it to meshlab the cloud doesent show up - i tried the icon for "dots" but it did'nt help. Everything works just fine if i remove the RGB and I-parameters when exporting from PT - but colors and intensity is no longer present for obvious reasons.

My question is - in wich order does meshlab read the XYZ-file, when export from PT it looks like this:
X, Y, Z, R, G, B, I
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Re: Export XYZ fail

Postby Jamesrye » Fri Jan 13, 2012 9:26 am

I have found that if you export in .ptx format, you can then import with RGB values to Meshlab.

Click file, import mesh and then select 'keep only points' on the Pre-Open Options screen.

Next, wait for the points to load and then click on the dots to view points.

From then on, compute normals and then use poisson reconstruction. A 64bit PC helps.

If anyone as experience with using the automated algorithms to prepare a nice looking mesh without copious manual editing then please can you post some details. There are some other useful tutorials on YouTube.

Hope thats helpful.
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Re: Export XYZ fail

Postby jedfrechette » Fri Jan 13, 2012 8:23 pm

kallek wrote:My question is - in wich order does meshlab read the XYZ-file, when export from PT it looks like this:
X, Y, Z, R, G, B, I


You probably don't want to use an xyz file. If I'm not mistaken Meshlab expects "xyz" files to contain either 3 or 6 columns. The first 3 are the point coordinates and the optional second three are the x, y, and z components of the point normal vectors.

Fortunately, it is pretty easy to convert your text file into .ply file [1] that will do most of what you want. For your example you need to make sure that your columns are separated by white space, not commas, then add the following header.
Code: Select all
ply
format ascii 1.0
element vertex ##REPLACE_WITH_NUMBER_OF_POINTS##
property float x
property float y
property float z
property uchar red
property uchar green
property uchar blue
property float intensity
end_header


Note that, as far as I can tell, Meshlab doesn't allow both intensity and RGB in the same file. If you specify both, as described above, you will lose your RGB values and get a greyscale point cloud colored by intensity.

Jamesrye wrote:I have found that if you export in .ptx format

...clip...

From then on, compute normals and then use poisson reconstruction. A 64bit PC helps.

If anyone as experience with using the automated algorithms to prepare a nice looking mesh without copious manual editing then please can you post some details.


Poisson surface reconstruction can make some really nice meshes, especially if the target is relatively smooth and continuous, but it's not so great for thin details, like cables, that are approaching the sampling density. One hint, whenever possible try not to calculate point normals from a raw unorganized point cloud. If you are importing a range image format like ptx it already contains implicit information about the normals, which is likely better then what you could calculate from a completely unorganized point cloud.


[1] http://paulbourke.net/dataformats/ply/
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PLY point compression ?

Postby lastools » Fri Aug 10, 2012 3:42 pm

Hello from @LAStools,

Jed, are you - or other readers - regularly working with big PLY point files? I am wondering if it will be worthwhile to add PLY support to pointzip, a compression utility currently tailored for gigantic point clouds in the PTS and the PTX format (see below for a screen-shot of the GUI). Is PLY a commonly used format in the terrestrial scanning community for exchange or storage of points?

Regards,

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Image

jedfrechette wrote:Fortunately, it is pretty easy to convert your text file into .ply file [1] that will do most of what you want. For your example you need to make sure that your columns are separated by white space, not commas, then add the following header.
Code: Select all
ply
format ascii 1.0
element vertex ##REPLACE_WITH_NUMBER_OF_POINTS##
property float x
property float y
property float z
property uchar red
property uchar green
property uchar blue
property float intensity
end_header
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Re: Export XYZ fail

Postby jedfrechette » Fri Aug 10, 2012 6:13 pm

I do use .ply files regularly but they're mostly used as an intermediate format for transferring data, usually meshes, between programs so being able to store them as a compressed archive isn't terribly useful. Presumably the mesh topology would also be lost by converting them to LAS.
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PLY point compression ?

Postby lastools » Fri Aug 10, 2012 7:05 pm

Hello from @LAStools,
jedfrechette wrote:I do use .ply files regularly but they're mostly used as an intermediate format for transferring data, usually meshes, between programs so being able to store them as a compressed archive isn't terribly useful. Presumably the mesh topology would also be lost by converting them to LAS.

Jed, of course. I was only talking about PLY files that solely contain point data (aka PLY "meshes" with only "vertices" but no "faces") as in your example above. The pointzip compressor targets laser scanning point data, not meshes. Is PLY often used for storing point data?

While on the topic of triangle meshes - most of my graduate work had focused on mesh compression such as the OOC compressor or the SMC compressor. What triangle mesh formats do you commonly use?

Regards,

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