Model File

Normally, the model of a robot or environment object handled in Choreonoid is generated by loading information previously written to a file as a Body item. The file contains optical information, such as the shape and color of the model, the joint structure, physical parameters, sensor information, etc. This file is called a “model file”.

Although various model file formats are defined by robot software systems, Choreonoid currently employs the model file format defined by the robot simulator “OpenHRP” as the standard format.


OpenHRP is an open architecture robot simulator whose initial version is originated from the “Human Cooperation/Coexistence-Type Robot System Research and Development” project conducted from 1998 to 2002 by the Ministry of Economy, Trade and Industry. Beginning with version 3 ( OpenHRP3 ) released in 2007, it is published as open source software. It has been used in many cases in research and development on biped robots in particular, and also has contributed to the development of biped humanoid robots, such as “HRP-2”, “HRP-3”, and “HRP-4C”. The kinetics simulation function of Choreonoid is being developed to be the successor of OpenHRP3.


Choreonoid is designed to allow a plugin to add a function to import model files in a different format. We would like to extend support to frequently used formats other than OpenHRP in the future. As part of this effort, a load function for the “Collada Robot Extensions” format is also implemented at present. However, this implementation is not complete yet and loading may not be performed successfully. Therefore, use the OpenHRP format for now unless there is a special reason.

The following describes the specifications of OpenHRP model files, which are in the standard model file format, and how to write additional information to use them in Choreonoid, mentioning the contents of the sample models.