Spring "joint"

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There should be a spring joint supporting hooke's law, and damping.
Obviously a massively useful component, but I discussion I had with
Chipmunk's slembcke convinced me that the damping part is not well/easily
implemented by users outside of the joint system, as damping is essentially
a velocity constraint, like motors.

Original issue reported on code.google.com by sadwanm...@gmail.com on 29 Nov 2009 at 3:22

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Isn't this covered by the distance constraint? See the Web example.

Original comment by erinca...@gmail.com on 5 Dec 2009 at 8:01

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Ah, yes it is. I was aware of the example, but it wasn't clear to me that it 
was a
hooke spring, without the familiar k,d terms, particularly when frequencyHz is
described as the "response speed", not the frequency of free oscillation, and 
the
distance joint docs don't mention this capability. Could you consider amending 
the
docs a bit. Perhaps add a getter/setter in terms of k as well as frequency.

Original comment by sadwanm...@gmail.com on 6 Dec 2009 at 11:06

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I will improve the documentation.

k and frequency are related by the effective mass, which isn't known until the 
joint is simulated. 
Also, my experience is that it is much more intuitive to tune game entities 
with frequency rather than 
some stiffness coefficient. The user generally has no idea about the effective 
mass.

I implemented setter/getters for the frequency and damping ratio.

I'd rather not implement a pure spring/damper connection because these can 
easily blow-up, even with a 
symplectic integrator. The distance joint is using a soft constraint that has 
greatly improved 
stability.

Original comment by erinca...@gmail.com on 7 Dec 2009 at 8:30

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I added documentation for the soft distance joint.

Original comment by erinca...@gmail.com on 3 Apr 2010 at 5:34

• Changed state: Fixed

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Maybe the frequency is equal to 1/2π*(K/m)^0.5

Original comment by shayn...@gmail.com on 26 Jul 2013 at 7:48