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dimforge / nphysics

2 and 3-dimensional rigid body physics engine for Rust.
https://nphysics.org
Apache License 2.0
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URDF, SDF, MJCF Model Loading #268

Open cmuell89 opened 4 years ago

cmuell89 commented 4 years ago

Hey all,

I am curious if support exists, or will in the future, for the loading of URDF, SDF and/or MJCF model files into nphysics. This functionality would make nphysics highly desirable for simulating robotics and help Rust expand into the robotics world in general. This is something I could potentially help with if there agreement to support such model files.

Perhaps the library is still too young in that it is missing a large variety of joint types, motor types, and sensor types etc,. to make URDF loading of models feasible.

sebcrozet commented 4 years ago

Hi!

There is no support for any file format in nphysics yet. And adding these would be a great contribution!

Regarding missing features, what types of joint types are missing exactly? I believe nphysics supports most types of joints with most combinations of degrees of freedoms. Perhaps there are some robotics-specific joints I am not aware about?

What are you referring to with "sensor types"? nphysics has a concept of sensors for collision detection without any effect on the simulation state, but I guess that's not what you call sensors?

Would it be possible for you to give a more detailed list of the missing feature to cover what URDF needs?

cmuell89 commented 4 years ago

I was referring to the fact that the README mentions some limitations due to the age of the library: "more joints, joint limits, joint motors and breakable joints". My comment was really the opening for a discussion about whether asset files like URDF etc,. are supported. W.r.t. robotics, this would make the use of this physics library much more desirable, but might also be suitable for other applications utilizing other asset files.

What is your opinion of adding additional dependencies? https://github.com/OTL/urdf-rs

Ralith commented 4 years ago

Is there any reason these need to be baked in, rather than maintained as an independent crate? It'd be nice not to increase the build/maintenance load for all the users who aren't doing robotics research.

cmuell89 commented 4 years ago

There is no particular reason. Certain physics libraries will offer support for the loading of model files and URDF is a common format for certain applications. Maintaining a separate crate seems like an appropriate choice. I am not very familiar with Rust and so I'll have to evaluate my ability to contribute. We can close this for now if you'd like, and perhaps I or someone can reopen if a good approach is implemented as an available add-on package/crate.

sebcrozet commented 4 years ago

@cmuell89 Looks like the README is slightly out of date. I don't think we need any more joints. Though it is true that not all our joints support motors and limits yet.

I agree with @Ralith that it would make sense to put this on a separate crate. Though this separate crate could be located on the same github repository as nphysics itself if we want to make its maintenance easier (to always keep it in sync with the latest nphysics version).

We can close this for now if you'd like, and perhaps I or someone can reopen if a good approach is implemented as an available add-on package/crate.

Let's keep this open so it is clearly visible in case someone else wants to try implementing this, unless you manage to do it yourself. Feel free to ask here on on the rustsim discord if you have difficulties working on this!

neachdainn commented 4 years ago

I am working on a (mostly functional at this point) URDF loader for nphysics. I am currently trying to get permission from my advisor to release it as open source, so it may not be available for a few months.

neachdainn commented 4 years ago

As an update, the loader I have works and I'm pretty happy with it and I should hopefully have it released as OSS by the end of October. A few notes, though: