The initial velocity of particles can be set through different parameters, based on the type of the particle system. If the particle system type is Emitter or Hair, then the following parameters give the particle an initial velocity.
The emitter's surface normals (i.e. let the surface normal give the particle a starting speed).
Let the tangent speed give the particle a starting speed.
- Tangent Phase
Rotates the surface tangent.
- Object Align
Give an initial velocity in the X, Y, and Z axes.
X, Y, Z
- Object Velocity
The emitter objects movement (i.e. let the object give the particle a starting speed).
Gives the starting speed a random variation. You can use a texture to only change the value, see Controlling Emission, Interaction and Time.