displaz is a cross platform viewer application for displaying LiDAR point clouds and high level features deduced from such point clouds. The interface and internals are optimised for viewing airborne laser scans of geographic data (see, for example http://www.liblas.org/samples/autzen-colorized-1.2-3.laz), but should also work for medium sized point clouds taken from other sources.

displaz is intended to be a highly flexible technical tool for exploring LiDAR data sets and higher level geometric features arising from them. Modern OpenGL is chosen for point rendering to put the power of the OpenGL shading language in the hands of the user: Shaders can be edited in real time in the shader editor to provide the most useful visualisation for the task at hand.

Use File->Open to open a las file - for example files, see http://www.liblas.org/samples. Note that displaz may appear unresponsive when loading very large files - just wait for it and it should eventually finish.

• Click and drag the left mouse button to rotate
• Click the middle mouse button to centre the camera on the closest point under the mouse
• Click and drag the right mouse button to zoom, or use the mouse wheel

To change how the points are displayed, use the controls in the box on the right hand side of the screen. Examples:

• To change the point radius, click and vertically drag on the arrows of the spinbox labeled "Point Radius". This extension works for all spinboxes containing real numbers; somewhat nonstandard but extremely convenient.
• To view in colour, select "Colour" from the Colour Mode drop down box.

Additional point display controls may be added and configured at runtime via hints in the the shader program. While in the shader editor (accessible via the view menu), pressing Shift+Return will cause a valid shader to be recompiled and applied to the point cloud immediately.

The primary file format is the ASPRS .las format; compressed .laz is also supported. Internally these formats are read using the laszip library (via LASlib) so any standards-conforming las file should be read correctly.

Very basic plain text import is also supported: Each line of a .txt file will be interpreted as X Y Z ... where the trailing part of the line is ignored.

Basic support for vector geometry (meshes and line segments) is available via the .ply file format. Any .ply file containing a header of the form:

element vertex <N>
property float x
property float y
property float z
element face <M>
property list uchar int vertex_index

will be recognised and rendered as a mesh with solid faces. When the face element is replaced with an edge element in the same format, each edge will be rendered as a set of linear segments.

displaz is intended to be cross-platform, and is known to run on both windows and linux. The author doesn't have access to an OSX system, but welcomes contributions toward making things work there as well.

The intention is to use modern OpenGL (at least version 3.2) for all rendering tasks. This gives us a lot of power via the OpenGL shading language, but presents additional portability challanges. displaz is known to work well with recent NVidia and ATI graphics cards and drivers. Some issues have been observed with intel integrated graphics and older ATI drivers - these will be addressed in the future where possible.

Behind the scenes displaz uses code written by many people. The following third party projects are gratefully acknowledged:

• Qt - http://qt-project.org
• LASLib - http://www.cs.unc.edu/~isenburg/lastools
• ilmbase - http://www.openexr.com
• rply - http://www.impa.br/~diego/software/rply
• GLEW - http://glew.sourceforge.net/
• Small pieces from OpenImageIO - http://openimageio.org

Before building, you need the following

• cmake >= 2.8
• Qt >= 4.7 (however Qt 5.0 and greater is not supported yet)
• GLEW >= 1.5.2 (or so)
• Python docutils (optional - required to build the html documentation)

The additional third party libraries are downloaded and built automatically by the build system (LASlib and IlmBase), or included with the displaz source code if they're small enough.