ok thanks!
About the collision detection : you DON’T have to do any collision detection as YOU control the snowflake and YOU control the static items : the landing point and lifespan of the snowflake can already be computed at its generation. Collision detections are only needed when dealing with user/player-controlled objects.
Originally posted by bzarokian:
the landing point and lifespan of the snowflake can already be computed at its generation.
What? do the collision detection every time you generate a snowflake? Heavy snow would cause a lot of collision queries…
Or generate all snowflakes and associated collision points at load-time, in which case that’s a lot of snowflakes to store for a whole city!
Originally posted by knackered:
What? do the collision detection every time you generate a snowflake?
Everytime you create a snowflake, you say its going to fall from point A and land at point B. Then just have it follow some sort of path between the points.
Yes, I get that bit!
I suppose you’ll only be calculating this path at most once a frame, otherwise it would be a blizzard!
I will not do a collision detection because it is not for a first personn game 
but a strategie game so 
thanks