To compile the decimater, you need to install a c++ compiler, Qt sdk
For Ubuntu / Debian users :
apt-get install cmake g++ qt-sdk
First step is to install OpenMesh in release mode. Download the archive from this page, Once you have downloaded the tar.gz file just uncompress and build it with following commands:
tar -xvf [tar.gz file]
cd [uncompress folder]
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release .. && make install;
Once OpenMesh installed, the decimater can be built :
mkdir build && cd $_;
qmake ../src/OpenMeshDecimater.pro && make