Integrating Soft Bodies with Articulation Bodies

[Haim_MCAI]

Hello, I am been attempting to integrate OBI Soft bodies with a robotic arm that is controlled with an IK solution. The arm fingers has obi colliders with high friction but I am having many difficulties interacting with soft bodies. Is there any "Best Practices" or somebody with experience with such systems that can drop some advice on how to approach this?

[josemendez]

Hello, I am been attempting to integrate OBI Soft bodies with a robotic arm that is controlled with an IK solution. The arm fingers has obi colliders with high friction but I am having many difficulties interacting with soft bodies. Is there any "Best Practices" or somebody with experience with such systems that can drop some advice on how to approach this?

Articulation bodies are not supported by Obi, only rigidbodies + joints are.

Kind regards,

[josemendez]

To add to my answer: articulated bodies work in a completely different way compared to rigidbodies + joints. In an articulated body the entire chain is considered a single body, and articulations add DOFs to it. The data for each link is expressed in reduced coordinates (usually w.r.t. another link). Impulses applied to one part of the chain are instantly propagated across the entire chain, calculating the change in linear/angular velocity for each link.

Rigidbodies however are individual bodies, their data expressed in maximal coordinates (usually world space) and generally with 6 DOF each (3 positional, 3 rotational). These DOFs then get coupled to other rigidbodies' via the use of joints, which impose restrictions on how rigidbodies can move relative to each other.

So intuitively speaking, articulated bodies work by adding DOFs to a single body, while rigidbodies + joints work the other way around: by removing/coupling DOFs from multiple bodies.

As far as Obi is concerned, this means that impulses are not applied the same way to a rigidbody than to an articulated body. Moreover, extrapolating the position/orientation of a rigidbody and an articulated body is done differently. As a result, two-way coupling with particles only works for rigidbodies.

kind regards,