[Feature]: MJCF Parallel/Close-loop Mechanisms Support

[CosmosMount]

What feature or enhancement are you proposing?

When I tried to build my robot with close-loop mechanisms in genesis, I found it did not work well like in Mujoco. Although the connection of most joints worked well, the most significant closed part of joints could not be solved. The comparison images are attached.

Mujoco	Genesis

Motivation

As a [e.g. civil engineering researcher working on flood simulation]
I want to [e.g. be able to simulate city-scale fluid / terrain simulations]
Because [e.g. this enables the efficient design and validation of flood protection structures].

Potential Benefit

Thanks for your great work and more support of close-loop mechanisms might be an outstanding advantage.

What is the expected outcome of the implementation work?

Perfect close-loop support like in Mujoco

Additional information

No response

[duburcqa]

Do you have a standalone reproduction script?

[CosmosMount]

You can refer to https://github.com/CosmosMount/wbr_genesis.git. Thanks!