GraspIt2URDF

Simple Python utility to convert hand model from GraspIt! to a ROS-compatible URDF. An example of the conversion of HumanHand20DOF.xml from GraspIt! is included.

Quick demo

• Install GraspIt!
• Install the urdf_tutorial ROS package
• Run python graspit2urdf.py --input_filename ${GRASPIT}/models/robots/HumanHand/HumanHand20DOF.xml from the scripts directory. This will produce a URDF file for the 20-dof Human Hand from GraspIt! in the urdf directory.
• Run roslaunch urdf_tutorial display.launch model:=urdf/HumanHand20DOF.urdf from the root of this repository. You should see GraspIt!'s 20-dof human hand model in Rviz, with sliders to manipulate the joints:

Converting a GraspIt! hand to URDF

• Create a directory in data, named with the GraspIt! robot name (e.g. HumanHand20DOF). It will hold the meshes and data files for your URDF model.
• Convert all .wrl files from ~/.graspit/models/robots/<ROBOT_NAME>/iv into .stl files of the same name (using Meshlab) and save them to data/<ROBOT_NAME>.
• Next, you need to find the inertia tensors and centers of mass of all the links.
  • I have included a Meshlab script that computes these for you. In short, it first closes holes in the link mesh, ensures watertightness by doing a simple Poisson reconstruction, and then computes the required quantities.
  • You can run it like so, from inside data/<ROBOT_NAME>: meshlab.meshlabserver -s info_script.mlx -i thumb2.wrl.
  • It should print out the required physical quantities towards the end. You need to make a text file of the same name (e.g. thumb2.txt) containing the inertia tensor on the first line and the center of mass on the second line. See the included example files in data/HumanHand20DOF.
  • For info about which values to include, see this article. The 1/s^5 scaling mentioned in that article is already implemented in the code.
• Next step is to convert! Run e.g. for the human hand: python graspit2urdf.py --input_filename ~/.graspit/models/robots/HumanHand/HumanHand20DOF.xml, and it should create HumanHand20DOF.urdf in the urdf directory for you.
• You can test this URDF in Rviz by first installing the urdf_tutorial package and running roslaunch urdf_tutorial display.launch model:=urdf/<your-urdf-file>.urdf, as mentioned in this ROS Wiki article.