Oh, I see. That's what my particle system does to avoid  I/O, but I didn't
implement particle-particle-interaction, cause parsing times would rise even
more. Given my experience with that kind of approach, I'd say that Shay uses
I/O to only track interactions within a given timeframe (which, depending on
velocities, may easily rule out several of the interactions that would
theoretically be possible). Aside of that, parsing times will sky-rocket the
higher the particle count (quadratic) unless some clever switches take care
of ruling interactions out better than calculating it.

Hey, Shay, how do you calculate interaction between two parabels? Like, when
two particle drop due to gravity, but also have a sideway-velocity? I'm
interested in the math behind this.

-- 
Tim Nikias v2.0
Homepage: http://www.digitaltwilight.de/no_lights
Email: tim.nikias (@) gmx.de


> The quadratic I was talking about (for 2D):
>
> d = sum of radii of the two spheres
> dvx = difference in sphere x-velocities (e.g. xv1-xv2)
> dvy = difference in sphere y-velocities
> dx = difference in sphere x-positions
> dy = difference in sphere y-positions
> t = time
>
> The quadratic is:

>
> You need to find the solution that is

> since the other solution:

> is the time at which the balls (had they gone through each other) would
separate the 'other side' of
> the collision. Note that if the value of t is negative, it means that the
collision has 'already
> happened' - i.e. the spheres are going away from each other. Since they
won't collide again on their
> present courses, this case can be ignored.
>
> -Chris
>

>
>


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