How does KSP do physics between parts so smoothly?

[ThaHypnotoad]

We may notice that sometimes no matter how many struts we put our rockets are still wobbly.

I've been working on something of my own that requires physics and found that Unity's joint system doesnt quite work as expected, with "fixed" joints sliding around and such.

I noticed that KSP seems to have solved the problem of connecting separate rigid bodies together and I wanted to ask, did the team:

1,) somehow implement Unity's joint system such that it would... well... work?

2,)make their own system for connecting components? In which case I was wondering if it was possible to get some insight into how it works.

[Bandus]

While I am not a developer, I can say that this video provided me some interesting insight into the development process of KSP: https://www.youtube.com/watch?v=mXTxQko-JH0

[GluttonyReaper]

Well ... it hasn't always been like this. 0.23.5 was where joints were really solidified, before that putting too much weight on the engines of a rocket would cause them to slide around in ways that didn't seem so natural (which, IIRC, is why launch clamps exist at all).

There's some dev notes on it buried somewhere, can't find them for the life of me though.

[StarManta]

(Also a Unity dev)

At one point I solved this by using a Hinge Joint instead of a Fixed Joint and just setting its properties so that it doesn't actually hinge at all. Hinge Joints are just plain better....

This was many moons ago, I can't say whether that's still the case.

Edited January 7, 2016 by StarManta

[magico13]

You could look into the Kerbal Joint Reinforcement code. If you look back to a version of the code from before 0.23.5 you'll see what the devs did in 0.23.5 (AFAIK they did the same things that Ferram figured out in order to reduce the wobbliness). Looking at the KJR code anyway might give you some ideas.

[ThaHypnotoad]

Hinge joints you say? That is, in fact rather strange. I'm going to try that out.

I do remember the sliding around when it was still in the early 0.2s. Didnt even notice they fixed that since ive been out of the loop for so long.