Hi Ricbot, From what i've understood, the physics engine included in Metacreations' Carrara was licensed from another company . Now, Eovia needs to license it again to include it to the next version of CS . So currently, Carrara Studio doesn't have physics, but it's planned . But users of the first Carrara that was released by Metacreations can still use the physics engine with CS . The particle emitter is very limited . There's a lot of reasons . The particles are not free so if you move the emitter, all the particles move with it . They can bounce only on the floor, not on an object of the scene . Also, we're stuck with limited shapes of 3D particles, and can't use 2D particles or objects . One last thing, it's hard to set shading properties that change with the time, for simulating a fading particle, for example . With all these limitations, you can't simulate much things with the particle emitter . Snow ? Sometimes your flakes will appear flat . Rain ? If you don't need the rain to bounce on a leave or something . Fire ? The flames at the top of the fire dissapear suddenly . Bubbles ? No way to make a particle look like a sphere . A flame thrower ? Don't even think about it ... You see . Very limited, as i said :( litst