Introduction to particle systems
All graphics and effects we have created so far use static meshes—3D models that can’t be skewed, bent, or deformed in any way other than by using shaders. Fluids such as fire and smoke can’t always be represented using this kind of mesh, but we can simulate these effects with a combination of static meshes, and this is where particle systems are useful.
Particle systems are objects that emit and animate lots of particles or billboards, which are simple quad meshes that face the camera. Each particle is a static mesh, but rendering, animating, and combining lots of them can generate the illusion of a fluid.
In Figure 11.1, you can see a smoke effect using particle systems on the left, and on the right, the Wireframe view of the same particles. There, you can see the quads that create the illusion of smoke, which is done by applying a smoke texture to each of the particles and animating them, so they spawn at the bottom...
