Miarmy provide an interesting emitter can emit the rigid body dynamics, we call them RBD emitter. The RBD object emit from this emitter can interactive with agents, terrains, kinematic primitives and Maya field/fluid, also the Miarmy force field.
RBD emitter example 1
RBD emitter example 2
This emitter can be created from Miarmy > Physics > Create RBD Emitter, the emit type for current version only have "Plane", it consist of a plane and a direction pointer to the emit direction. Like the picture below:
The RBD emitter
The RBD emitter can be freely transformed, translate, rotate or scale is no any problem.
Scaling bigger to emit the rigid bodies scatter. The RBD objects will be always emit from the plane area.
Scale freely
Rotate freely
The rigid body emitter have some attributes can be adjusted to achieve different emitting result, and most of the attributes can be keyed frame.
RBD emitter attributes
Emitter ID: control the color of object emit out. (we will extend this feature later) 
Emitter ID: 2 (left) 6 (right)
Display mode: control the constant color or diffuse color
Display Mode: plain (left), normal (right)
Contact event: control the how the rigid body interactive with the scene element, we will talk about this in next session because there are some concepts need clarify before talking this.
Rate: control the number of emit each frame
Rate: 1(left) and 50(right)
Rotation speed, rx: 0.0 (left) rx -0.2(right)
Box shape attributes XYZ adjust the dimension of XYZ of rigid boxes.
Box shape attributes: x:1 y:10 z:1 (left) x:5 y:5 z:5 (right)
The sphere and sphere shape is not available in this version, even the attribute still there. We'll add sphere shape later;