Expose joint damping_ratio and natural_frequency per joint to make joints soft

[Ughuuu]

There have been 2 issues about PinJoint2D not having softness like Godot has. Rapier just doesn't support per joint softness, so as a workaround you can change the following project wide properties:

• physics/rapier/joint/damping_ratio
• physics/rapier/joint/natural_frequency

These will help to make soft joints (eg damping ratio 0.1 and natural_frequency 50).

However, there isn't a way right now in rapier to set these per joint. Here is linked issue in Rapier dimforge/rapier#676

Also, in order to expose new properties (on the joint directly) and hide the softness, this one needs to be solved first: godotengine/godot-proposals#10438 (comment)

[GeminiSquishGames]

(eg damping ratio 0.1 and natural_frequency 50).

I noticed the range sliders only go from 0 to 10, but started at some huge amount. I guess enter by hand is the key.

[Ughuuu]

I can update the range sliders limit, maybe I set it from 0 to 10 by copy pasting other properties. But in any case, this is how most likely softness will be done in godot-rapier. If you want to test it for now until it's done per joint, you can give it a try see if you like it. Another way to make it more reactive is to try:
damping_ratio: 0.8
natural_frequency: 40

Also mass has some importance I think.

[GeminiSquishGames]

Yeah, I'm using mass quite a bit and noticed I have to use rather lower values. Physics toy, high progression potential, Roguelike, Solar Jetman space shooter type thing. Which reminds me, I notice the units are 100, is that pixels and does that effect linear velocity?

So far this works and feels fun, but that's probably subjective. I can at least move them around without it feeling weird and stopping the ship or the asteroid immediately. I suppose the tractor beam doesn't really need upgrades like weapons and thrusters or other ship modules, but I thought it might be fun for multiplayer mode to have variance, but it's not a deal breaker at all.

[Ughuuu]

The units are 100, that is how many pixels equal 1 meter. It affects some things, unsure if it affects linear velocity though.

[GeminiSquishGames]

I will test things and scale as needed. I'll probably have to scale up things a bit, if the mass is accurately in kilograms then things should be okay as long as I can stick to the scale, but the lack of z dimension probably leaves room for arbitrary approximations. Damage on impact is calculated with velocity, though the linear_velocity is always what it is the frame after the collision, so I have to grab it on the physics frame just before (another one of Godot's wacky things) . As is it's pixels per second, or if I do it by position each frame manually, pixels per frame. I was going for 128 p/meter so not far off, just to stick with general texture standard powers of 2.

[Ughuuu]

Will merge dimforge/rapier#789 into Ughuuu/rapier fork to have it faster so that I can implement it here.