What is HAPI?

From H3D.org

HAPI is an open-source, cross-platform, haptics rendering engine written entirely in C++. It is device independent and supports multiple currently available commercial haptics devices. You can write your application once and not have to modify any code to use another haptics device. Choose between different rendering algorithms, different force effects and several kinds of surfaces to create the feeling that you want or create your own custom made effects. HAPI has been designed to be highly modular and easily extended.