"Tim Nikias" wrote:
> I've just implemented a "wind turbulencing algorithm",
> which takes care that particles born nearby are blown
> in a pretty similiar direction, but this changes subtly
> based on initial position.

I think something looks fundamentally wrong in this animation. Each particle
starts still but then accelerates in a specific direction. But what is it
that pushes the particle in the same direction all the time? It doesn't make
sense that the wind keeps pushing a particle in the same direction; as the
particle moves, it would enter different air streams and change direction,
or more likely eventually just follow the global wind direction. But your
particles keep accelerating in the direction they started with, or at least
it looks that way.

> There are two gaps though:
> When the rocket passes the x-axis, the smoke-column
> breaks apart. Particles move upward, and then suddenly
> downward.
>
> I am using always the same algorithm:
> -take a turbulenced vector and the initial wind direction
> -create an axis using vcross with those two vectors
> -using another smooth-turbulenced float, rotate the initial
>  wind direction about some degrees around the former
>  calculated axis

This seems overly complicated. I suggest.
-take a turbulenced vector and add it to the initial wind direction. And
that's it.

You will also avoid the problem with vcross this way, so you should get no
abrupt changes.

Rune
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