Fire Ball collision

ok how do I make this kind of thing…

Example dragon thought a fire ball against some thing (wall, shield what ever), so any one know how do I animate this… Fire Ball fly to target and hits it, and then disperse its self flat, like on the shield.

I know how to make fire boll useing particles but how to make collision…
Plz help

hehe, it might be cool to do this with the fluid system…

Dragon picks up ball called Particle Emitter textured with fire and throws it. Ball hits sheild and disappears onto Layer 20. On the same frame Particle Emitter.001 (with copy of texture) moves from Layer 19 to sheild.

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