Misalignment and jitter

vako

Hey, so I'm kinda new to godot just started a few days ago and decided to make a project I've been working on for a while already, this is basically a four bar linkage mechanism simulation, the idea is that I can simulate any four bar linkage mechanism without problems and gets its position, velocity and acceleration

The way I'm constructing the mechanism is by having an scene being one linkage and then in a scene called Mechanism I use the script to add 4 childs being each of the four linkages (stand, input, coupler and output), then I calculate its initial position and just make it move at a given speed

These are the equations I'm using to calculate its positions:

The bottom linkage is static (stand), the one most to the left (the input) is moving and the other two move in accordance to those formulas (the coupler and output)

And this is what it ends up looking like:

Using basic principles of vector math what I do is that both the stand and input share an origin, the coupler has its origin on the tip of the input and the output has its origin on the tip of the stand, but as you can see in the image the coupler doesn't align with either the output or the input, I'm not sure why is this, my only guess is that is due to the precision of the floating points or something else

So, I'm kinda just asking if any of you have an idea of what could it be or you could find a workaround?

dotted

First I might doubt it's a precision issue unless the scale on the objects is in the mm range.

I have a few questions though.

The math and coding needed to handle constrained motion are relatively sophisticated problems. In essence you are either hand coding a physics simulation or solving a 3 link IK problem.

Are you trying to master the math for it or just achieve the result?

In the former case, I would recommend reading up on physics simulation or the various existing ik solvers.

In the latter case, I would recommend using the physics engine or utilizing one of the IK packages available for godot in the assets lib. In the case of the assets lib, you can look at how it was implemented for your own edification

vako

Sorry I didn't know how to erease the question or anything, and I've search for this kind of solvers and there are none that properly resembles what I want to do (this is actually a project for college) In this case I found the problem was not the math at all, but rather the sprites I was using which weren't scaling properly giving me an extra error

dotted

Yeh there was a Fabrik solver at one point but it is gone.

However, the physics engine can also do the same thing.

TwistedTwigleg

If you are looking for inverse kinematics in Godot 3 and do not mind using the Mono version of Godot, then this plugin I made may be helpful :)