-[I still can't quite get this to look how I wanted it to look]-
How do you want it to look? At the moment it looks to me quite like what it
is a simulation of - that is a lot of masses connected by bungee cords. I'm
not sure quite how to make it look more like a single rope - possibly you
need a force which tries to straighten the links out - this probably ought
to be quite weak but highly damped.

Making the masses on the rope very much smaller might also help. This would
make the system more difficult to simulate though (smaller timesteps
required).

-[So what do ya think, folks?]-
Pretty impressive. Have you simulated any further in time in the simulation
that you've posted. It _looks_ as though it might explode to infinity at
some point - or at least it looks on the verge of being unstable. I may be
being overcritical of your algorithms though - you may have got it exactly
right with very little damping.

One way of checking this (which is used in scientific simulations to make
sure that the errors in the simulation are small) is to find an expression
for the total energy of the system, and to see if that is absolutely
constant, or whether it is increasing or decreasing. Just to insult your
knowledge of physics, you do this by adding up the potential and kinetic
energy, which are given by



m*g*h = the gravitational potential energy for each mass (m=mass,
g=acceleration due to gravity, h=hight above some arbitrary point)


length, where k is such that the force exerted by the spring is k*x and l is
the normal length of the spring. Note that since your springs never exert a
force outwards (if they're the same as your grid springs), this equation
only applies to your springs when x is positive (stretched spring)

If you have some damping, the energy should be decreasing. If you have no
damping, the energy should be absolutely constant. If the energy increases
continuously (even slightly), it means the the simulation is unstable - try
adding damping or shortening the step length.



-Chris

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