This is a three-dimensional emitter type and you can set values for all three coordinates. Please note that the scale values are linked and it is not possible to adjust three different settings for X, Y and Z. By default the particles are emitted from the sphere’s surface, but there is also an option for filling the entire volume. In the second case, the result is identically to a “Fill Object” emitter.
Speed
As always, “Speed” sets the initial velocity of the particles at creation time. Animated “Speed” values are often used to create all kinds of interesting effects.
Randomness
This parameter can be used to avoid patterns and regular structures by displacing the particles randomly at creation time.
Fill sphere
Since a sphere is a 3D object, it can be entirely filled with particles. By setting “Fill sphere” to “Yes”, “Speed” is set to 0.0, but it is also possible to initially fill the sphere’s volume and apply a new speed value afterwards. With “No”, the particles are only created on the emitter's surface and emitted with the adjusted “Speed” value.