# Fireballs, Collisions, and the Walls they effect

Ok let my start by giving away FAR too much information by saying that I just rented How to Train your Dragon and was inspired to try my hand at making the best fire and clouds possible in Blender.

Now back to the reason I’m making this thread: I’ve made a fireball using the smoke simulator with a set of particles fired from the emitter. The problem I am having is I want the fire to roll around obstructions like small pillars rather then just poof and disappear. My idea was to somehow make the particles themselves be effected by the obstructions and be displaced by them. I understand that normal geometry itself can’t effect particles but I don’t know what TO use. So if anyone has any ideas I’d be grateful.

You may need a large smoke box (the initial volume the smoke is created in) which will use lots of memory. And a particle system to create the fire/smoke trail. You would then alter the path and interaction of the particles by using force fields. Objects can behave as force fields too.

You could even draw a path for the particles to follow, make it wrap around stuf for example. Be aware that the fire may look blobby at the point that it originates, it depends on the resolution of the smoke box you define at the start. So it may help to make a seperate fire ball object to hide the emission point.

If you’ll click the word “Fireball” in my first post it’ll take you to a video on Youtube of my current “fireball”. Anyway I have both the Domain, Emitter and Particle System set up. My question was how to get the Particles to react to walls and such.

Your idea about Force Fields was a idea I had as well, but if I don’t have to use it I don’t want to. It seems too convoluted a solution.

You have to set the obstacles as collision for the smoke by selecting them and going physics tab > smoke > collision. If it’s too slow you can make lowpoly non-rendered objects act as collision instead of high-poly.

Well, the Particles went right through the “Collision” object, I’d mess with the settings but apparently the Collision tab doesn’t have any. I looked through the emitter’s Particle System and Smoke settings but couldn’t find anything that would link the Collision object to the particles.