Extend the Pin Joint to have angle limits and motor

[Ughuuu]

Describe the project you are working on

A custom godot physics engine for 2d with box2d underneath.

Describe the problem or limitation you are having in your project

I want the plugin that I am developing that is extending/replacing the use of Godot Physics 2D to use nodes to their full potential but also not make users use new nodes to do so.

I want to use some of the features that box2D has to offer in terms of joints:

• Revolute Joint: Similar to Pin joint. Has extra motor speed, angle limits. Has flag to enable angle limits and motor.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Update the PhysicsServer2D api to have angle limits and motor speed and possibly a flag for angle limits and motor speed.

The angle limits, at least for box2d, aren't common for all joint types, so adding it to a function like:
PhysicsServer2D.pin_joint_set_param() would be great.

The following params would need to be exposed:

• angle_lower_limit
• angle_upper_limit
• motor_speed

And for PhysicsServer2D.pin_joint_set_flag:

• motor_flag
• angle_limits_flag

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Not 100% sure of the implementation in godot 2d physics, as I am really interested in the box2d plugin only. If needed, I can look into this one as well.

If this enhancement will not be used often, can it be worked around with a few lines of script?

No. Except for adding a new node that does the above mentioned functionality, but then users won't be able to use it as a drop in solution.

Is there a reason why this should be core and not an add-on in the asset library?

This helps a lot of use cases that aren't possible with regular Godot Physics 2D solution.

[Ughuuu]

It would also help build rag dolls, having now angle limits. Also, issues that would benefit from this:

• Add "Glue Joint" or "Fixed Joint" #86
• Add motor/target_rotation property to Joint Nodes #3891
• Add angular_limit to PinJoint #4224
• Add Angular Limits for PinJoint2D Node #7520

This is similar to the last proposal here, but now it's based more on the box2d implementation, extending all they have(incl motor speed)