LAZ to PTX conversion

[Wilbert van den Broek]

My name is Wilbert van den Broek and I am a 3D generalist at ISAAC VR. For a new proof of concept we need to convert Lidar data in .LAZ format to

either .e57 or .PTX

The concept we are working on is to create a simulation game in vr for a race. The lidar data is created by another company. We want to use

Reality capture to create a polygon mesh, but RC only reads .e57 or .PTX. I tried to convert the .LAZ with PointUnzip but it only gives me .PTS

How can I get a .PTX file so RC can read it?

Thanks in advance.

[Martin Isenburg]

Hello,

it's not possible to map a *generic* LAZ or PTS point cloud to a PTX file as PTX files are *structured* or *gridded* points on a grid with a certain number of rows and columns. Sort of like a 2D image where you have instead of RGB and intensity value. Maybe it helps to intuitively visualize how points are arranged in space to consider having the rows and columns arranged as follows: Instead of in a flat 2D domain you have the rows and the columns somewhere projected  into 3D space like a slide projector that instead of shining onto a flat screen (like at your typical conference or meeting) will illuminate a complex scene at some tilt/roll/pitch angle and then record the xyz coordinates along with their intensities of where its rectangular beam illuminates the scene using a regular grid, hence also in rows and columns but each potentially at a different distance / range from the light source.  

Here some further info:

http://www.laserscanningforum.com/forum/viewtopic.php?t=5582

http://w3.leica-geosystems.com/kb/?guid=5532D590-114C-43CD-A55F-FE79E5937CB2

Summary: You can go from *structured* or *gridded* PTX to a *generic* LAZ or PTS point cloud but you cannot go in reverse unless (a) the points are on a grid and you know the grid parameters (cols/rows/rotation/offset) or (b) you resample your generic point cloud somehow onto a grid.

Regards,

Martin @rapidlasso

--
Download LAStools at
http://lastools.org
http://rapidlasso.com
Be social with LAStools at
http://facebook.com/LAStools
http://twitter.com/LAStools
http://linkedin.com/groups/LAStools-4408378
Manage your settings at
http://groups.google.com/group/lastools/subscribe

[Moysset, Miriam]

Hello,

 

If the LAS point cloud has been generated from correlation (regular mesh), LASTOOLS allows the transformation of LAS to PTX?

Thank you

 

Myriam

[Martin Isenburg]

Hello Miriam,

this will be difficult. There is no ready made workflow in LAStools. But PTX is just an ASCII file with x/y/z/intensity/(rgb) values per line in scanline / grid order and a small header. If you simply output your points to a TXT file with las2txt and then manually edit in the few values for # columns, # rows, translation vector, 3x3 rotation matrix and 4x4 matrix in the header and rename the file then it should work (assuming all points are there). The vector would be zero and the matrices the unit matrices with ones on the diagonals and zeros every where else.

Regards.

Martin