# Adding gravity to a volcano spewing ashes

Ok, here’s the latest project I am working on.

I built an island and a volcano spewing smoke. Now, what I’d like to do is add gravity to the smoke so that the smoke does not simply disappear in the air, but instead spreads out and maybe comes back down towards the terrain. Like it would in real life. That is, I want gravity to pull the smoke and ‘ash’ down and then disappear.

Is this even possible?

115610–4402–\$volcano_demo_122.html (6.16 KB)

hello,

try playing with the values in the PE inpector,
world, local, tangent velocities
you might get the effects your looking for

Ray

The particle animator values are what you are looking for. In particular, the force values. They add a velocity to the particles every frame causing acceleration, much like forces acting on a rigidbody. What you want is a negative y-axis force.

The emitter emits the particles upward and then the force value accelerates the particles back down.

Negative Y values… I didn’t think of that. I’ll give it a try in next hour and post my (successful) results.

Although I foresee a problem in a sense that instead of my particles going up they’ll be coming down into the volcano and into the terrain…

I have a theory on what might work instead combined with the negative Y values, but it’s going to be “ghetto-rigged” I think.

Your particles will go up if you provide them with an initial upward velocity (+y value). In the animator, you then add a -y force to them so that that initial velocity is dropped to zero and then negative values over time. I’d then apply a random or tangent velocity in the emitter in the x and z directions to make the particles go “out” from the volcano. I’ve attached a simple project with some sample settings (you’ll obviously want to reduce the energy/number of particles emitted for a real project).

115995–4413–\$volcano_208.zip (6.87 MB)