How to apply forces on points?

[lattice0]

Following my X shape test bevyengine/bevy#5698, where I use an X shape GLTF Blender mesh as a Collision shape, I now want to apply forces to one of the ends of the X shape. I couldn't find anything about forces.

I think first I need to learn how to mark the points where I'll apply the force. I don't know if it's possible to do it in Blender and then use in bevy_rapier.

Then I need to learn how to load these points in bevy and apply the force on one of these points

[sebcrozet]

bevy_rapier itself doesn’t have an helper function for the application of an ExternalForce component at a specific point. But, you can implement it yourself by computing the torque manually:

let force_at_point = ExternalForce {
    force: your_force,
    torque: your_torque.cross(world_space_point_of_application - rigid_body_position)
}

This assumes that rigid_body_position is the world-space position of your rigid-body’s center-of-mass.

[richardhozak]

As of bevy_rapier 0.17.0 there is ExternalForce::at_point implemented by sebcorzet, that does this calculation and can be used to apply forces at specific points of rigid body, I think this can be marked as answered.