Mass properties merged for parts fastened together

[stevenwman]

Hi,

I have a robot with most parts (approximately 4 per link) fixed to each other and a single revolute joint. I'm hoping to export a URDF file where I can tune the URDF mass properties of the individual parts (e.g. the foot is fixed to the leg but I wish to edit the foot mass independently from the leg mass in the URDF).

I noticed that I can enable a setting called useFixedLinks in the config.json parameters. When that flag is false, the URDF will have 2 links with 1 joint, where each link has multiple meshes attached. Each link will have a combined mass and inertia generated by the individual parts fixed together. When the flag is true, the URDF will have many links with many joints, where most are fixed joints and 1 revolute joint. However, it seems like there are still 2 primary links where the rest of the links are just fixed onto those primary links (only the primary links have the same mass properties from the previous case).

Please let me know if it's possible to export each part in the assembly (with their mass properties) despite being fixed to other parts so that in the URDF file, each link will only have one mesh with one set of mass and inertia. Thanks!