How can I make a slider joint completely restrict Z and Y movement?

ator-dev

I've been spending a lot of time trying to get slider joints work to firmly attach a hanging object to an overhead rail, such that it smoothly transitions between rails by detecting the closest one and attaching itself using joints. The amount of problems I've experienced so far has been huge, and my current one which I can't seem to solve is getting a slider joint to make the object only move along the X axis of the rail. Surely that's the whole point of sliders, unless I'm not understanding something here?

The object currently bounces up and down and from side to side, apparently being very loosely attached, which introduces a lot of other issues such as derailment almost every time it goes from being attached to one rail to another. Could someone please point me towards a solution, or a different way to approach rail/joint transitions?

TwistedTwigleg

Unfortunately, I have not used slider joint nodes myself, but I have dabbled a little bit with some of the Godot joints in 3D. One thing I find that is very important with joints in Godot, that is not mentions nearly as much as it should be, is that the position of the Joint and the origins of the RigidBody nodes (the actual RigidBody nodes, not their collision shapes or any other child node) matters a LOT to the result. I would check to see if your slider joint and your RigidBody nodes are all on the same plane on the X axis, that they all use the same X coordinate value, as that might be causing some issues based on my limited Godot joint experience.

ator-dev

@TwistedTwigleg Thanks for the reply! I'm still uncertain as to what's actually causing my problems, but what you said in your post reminded me about some joint behaviour that confused me yesterday. Currently my slider joints are inside the StaticBody nodes (which never move in-game, by the way) which they are attached to, and in this state they seem to keep breaking and causing the hanging object to fly all over the place. However, when not inside these nodes, they're completely fine - but because of the way my script accesses them, putting them somewhere else in the heirarchy will make things more complicated. I'll try remaking my code to use this system though, and will update you as soon as possible.

To be honest, for days now I've just been trying to move on from the hanging object rail-transition system. I'll be really pleased if I can finish off this final bug now and get on with the actual gameplay - unfortunately the way this operates is essential to the rest of the game, so it has to be working before I can do anything else.

ator-dev

@TwistedTwigleg I had some more ideas and put the system through a few more iterations, and now it works! Thanks for the help. I eventually achieved the desired effect by putting a static body inside the parent of the problematic rigid body, putting a slider inside that attached to both the static and the rigid body, then updating the static's transform to simulate the effects of straight and curved rails - the whole things looks flawless, and the physics are basically immaculate with the hanging object even keeping the right amount of momentum.

By the way - to anyone seeing this in the future, sorry if you wanted to find out how to make a slider restrict all Z and Y movement. I don't think the joint's designed to be able to do that, but you can do some pretty similar (and often more realistic) things by experimenting with using them in different ways.

TwistedTwigleg

Awesome! I am glad you were able to find a solution :)