[Paraview] I: 3D point cloud with color

[David Pont]

Hi Giulio,
  I am also very interested in viewing XYZRGB data, and I have not had any success in Paraview so far. I think the suggestion to use a vtp file instead of a text file was simply another way to get data in to Paraview. But I think the issue is how to use RGB values for coloring, regardless of how the information is read.

I hope I am wrong, but I don't think this is supported. Paraview (vtk) uses lookup tables to map scalar attribute data to RGB values. It also supports vector data, by using only one of the values, or magnitude, ie still a scalar to RGB mapping. When I load your example vtp file the RGB triplet is loaded as Normals_, and color options are then to use, X or Y or Z or Magnitude.

It seems like this should be easy, really we want to bypass the mapping of scalars to color and have Paraview (vtk) use the provided RGB directly. But I think this might require a completely new Mapper and/or other parts of the rendering subsystem. Probably quite do-able for someone that understands the inner workings of the rendering system?

In the meantime you might be better looking for other tools that are designed to display point clouds with RGB? This kind of data is becoming more common. My interest is for LiDAR data where XYZRGB data is starting to become available, but I have not actually encountered this yet so I have not found a solution.

Here's hoping I'm wrong and someone has a clever solution in Paraview... otherwise perhaps it could be a feature request?

  regards, Dave

David Pont
Scientist - Forest Management Science
Scion
49 Sala Street, Private Bag 3020, Rotorua 3046, New Zealand
DDI +64 7 343 5663
www.scionresearch.com



-----Original Message-----
From: paraview-bounces at paraview.org [mailto:paraview-bounces at paraview.org] On Behalf Of Giulio Reina
Sent: Monday, 27 February 2012 8:57 p.m.
To: paraview at paraview.org
Cc: andrew.amaclean at gmail.com
Subject: [Paraview] I: 3D point cloud with color

Hi all,

Following  David's suggestion, I came up with the code attached that turns the starting data file (rgb.txt, of the type [X Y Z R G B] (the first three vector columns specify the location of the single point and the last three one its color in RGB space)) into a parsed vtp format. Unfortunately, when I try to open the VTP file in Paraview (after applying a Glyph filter) the results are not what I expect, i.e. one point red, one point green, two points blue.

I would greatly appreciate if someone could help me put reading correctly the VTP file, I should admit that I'm not very familiar with the use of vtp files in Paraview,

Cheers

Giulio




-----Messaggio originale-----
Da: David Doria [mailto:daviddoria at gmail.com]
Inviato: giovedì 23 febbraio 2012 02:48
A: giulio.reina at unisalento.it
Cc: paraview at paraview.org
Oggetto: Re: [Paraview] 3D point cloud with color

>> I have been working with 3D stereo reconstruction. So, I have huge 3d
point clouds co-registered with color in this format [X Y Z R G B] (the first three vector columns specify the location of the single point and the last three one its color in RGB space). I have been trying to display the data in Paraview without success.

>>
>>
>>
>> I use the "table to points" filter to show the 3D coordinates but
>> then I
do not know  how to specify the color of each single point using its RGB components. Can you please help me out?

If you're more comfortable in c++ you could use VTK to parse the file, construct a polydata, and then write a vtp file. Here are the examples you'd
need:
http://www.vtk.org/Wiki/VTK/Examples/Cxx/InfoVis/ReadDelimitedFile
http://www.vtk.org/Wiki/VTK/Examples/Cxx/IO/WriteVTP

Then Paraview can easily read this vtp file.

David



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