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REX is an Augmented Reality platform enabling users to simple embed your 3D content into the real world. REX is cross-platform and supports a variety of different devices (e.g. iPhone, Android phones, Microsoft HoloLens). Once the 3D content is ingested, the models can easily be viewed by any devices using our free app REXview and REX Holographic

OpenREX is the open source toolkit for the REX platform. This repository contains all the necessary ingredients supporting REX develpers for getting started with REX.

This repository contains the REX format specification, native reader/writer written in C, tools for working with REX files, and debug viewer for displaying REX files.

Please also find a GO-based library here.

Getting started

In order to compile the code, you need at least a C11 compiler (e.g. gcc, clang) and cmake installed on your system. The code should work for Linux, MacOS, and Windows.

For compiling all tests, you also need to install check. You can simply use your package manager to install the test library (e.g. apt-get install check).


There are different cmake options which can be obtained from the CMakeOptions.txt file. The default behavior only compiles the REX library and the REX tools.

It is simple to compile the library on your system:

mkdir build
cd build
cmake ..
make install


The code uses Doxygen as documentation engine. To generate the documentation install doxygen and execute doxygen in the project's root folder. The output will be stored under doc/doxygen.

REX tools

Debug viewer (deprecated)

OpenREX contains a simple debug viewer which is able to show the geometry information of a REX file. Currently not materials are supported! Enable the viewer by

cmake -DVIEWER=on ..

The debug viewer requires SDL2 installed on your system including GLEW. Make sure to have the following packages installed (libglew-dev and libsdl2-dev).

Importer (experimental)

There is an experimental REX importer using the Assimp library which is currently not in full production yet. Contribution is welcome. To enable the importer use

cmake -DIMPORTER=on ..

Unity Package

We provide a package for Unity to read/write .rex files. See

Source code formatting

If you plan a contribution, please make sure to format your code according to the following astyle settings:

--style=allman --indent=spaces=4 --align-pointer=name --align-reference=name --indent-switches --indent-cases --pad-oper --pad-paren-out --pad-header --unpad-paren --indent-namespaces --remove-braces --convert-tabs --mode=c

Windows build

With Visual Studio 2017 you should be able to use the CMakeLists file directly. See

Contribution and ideas

Your contribution is welcome. Here are some ideas:

  • rex-dump: dumps a certain block to the stdout which can then be piped into other programs (e.g. feh)
  • Extend rex-info to support filtering (e.g. only show meshes, or materials)
  • Save images from REX to files
  • Continue to integrate assimp for data conversion

Guidelines and pre-requisite(s)

  • Keep it simple and follow the UNIX philosophy
  • You should be able to write robust C code
  • Make sure to format the code according to our style (see above)
  • Check your code for memory leaks using valgrind
  • Your code should run cross-platform (Windows/Linux/Mac)

Contributions and external sources

  • linmath.h for linear math operations
  • slash.h for reading LAS files
  • argparse for parsing command line arguments
  • cJSON for parsing JSON files (currently used in tools)

Please see the copyright notice in the according files.

The osm_polygons.json sample is extracted from Microsoft's building footprint which can be downloaded from:


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