The direction the cone is pointing, the angle of the cone, minimum and maximum speeds, and the uniform or pseudo-gaussian distribution for generating the initial velocities can be set. Smoke, for example, may be generated from a narrow cone pointing up in the scene, while fireworks exploding in the air may have a cone angle of 360 degrees. Controlling the Particles After being generated, a particle is affected by its environment. These factors include gravity, wind, attractors, paths and walls. Gravity The direction vector and acceleration value of gravity must be specified to indicate which way is down.
Gravity is considered constant across the entire particle system.
Wind Wind direction, speed, and viscosity must be specified. A particle will move in the wind in the direction and at the speed the wind is blowing. Wind viscosity determines how quickly the particle approaches the wind velocity. With wind speed at zero, for example, wind viscosity may be used to simulate air resistance to slow down movement. The use of attractors allows the creation of complex-looking particle systems with minimal authoring effort.