Wanting to attach a chain of rigid bodies to an animated and moving sprite.

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Wanting to attach a chain of rigid bodies to an animated and moving sprite.

Avencherus

I can't seem to reliably create any way to attach a chain to a node or sprite that is animated or moved by code.  All the physics seems to halt, or break. I can successfully construct a chain out of rigid bodies, and attach it to a sprite, and watch the parts swing, but when I try to move or rotate an instance of this setup, it doesn't do anything. I've also had to overcome that scaling doesn't seem to get passed along by rigid bodies to it's children, so I have to set those properties in GD script whenever the instance gets rescaled. Any ideas on what I can try, or what I'm doing wrong, or is this even an option?

Ross

Same for me too. I made an animation that moves the root body around. While it plays the chain links act like rigid connections, then as soon as the animation stops they spring back into simulation. Is that how it goes for you? I tried an animation and moving it by script. I would make a minimal example project and make a bug report.

Avencherus

It has some inconsistency to the nodes, but what I'm finding is that it seems to be very important that the root you pin to is also a physics body, I was using a Node2D originally.  In my case I got some success making a static body at the origin in the scene, and pinning the chain to it. In animation I could only get it to be active if I used discrete keyframes.  Continuous seems to shut it down.  At least when it comes to animating the scene directly.  I have more experiments and fiddling to do, and a few more ideas to try.  Stuff like what happens when you attach things to a kinematic body and animate it, etc. It's not a very well documented set of features, and Godot's general flexibility doesn't seem to happily extend into these areas with physics and constraint nodes. I already mentioned too, the rigidbody will not forward scaling information down to it's children by default.  So for now inside the root of my scene I have to manually step over it and assign directly using GDScript.  I think you can maybe even use the RemoteTransform2D node to bypass it too, but either way it can quickly become a lot of extra work. At some point I will probably just write a plugin node or some helper function to deal with it in my project. I guess it's been an issue since March 2015:  https://github.com/godotengine/godot/issues/1505 I wrote a ticket and it got closed as a duplicate:  https://github.com/godotengine/godot/issues/6242

Ross

Yeah, Godot's physics stinks, I really wish they just used Box2D. Ah, I just realized, in my test I was moving a Node2D that was the parent of the whole chain. Moving the base chunk of the chain seems to work fine, whew! Moving a Node2D with the base chunk(static or kinematic body) its child seems to work fine too, as long as the rest of the chain links are not children of that Node2D. It seems pretty buggy how Godot deals with rigidbody children of moving Node2Ds. It should just ignore the parent's movement entirely. Are you trying to dynamically change the scale of rigid bodies?

Avencherus

<a target="_blank" rel="nofollow">Ross</a> said:

Are you trying to dynamically change the scale of rigid bodies?

</blockquote>Not so much the rigid body node itself, but what it contains, a sprite and a collision shape.  So yes and sort of no. It can be assigned alright in the ready function, but I'm still trying to figure out if it's possible to change these things dynamically.  They seem to be going bonkers with the things I've tried so far. It would be nice to have a 2D character that has a size that can be scaled.  If it's not meant to be, then I probably have to construct some kind of invisible scene, and use it's coordinate information to do my own projection graphically.