In this tutorial I'm going to show you how to generate exploding pieces with particle instancer and particle expressions.
instance a object to particles
Select particle and object in this order
Particle > Instancer(Replacement)
The particles are replaced by the object.
The instanced geometry object can be
a single object, animated or not animated,
and can be a sequence of objects in different shapes or positions.
making exploding pieces
Emitte particles from sphere object as the above,
connect the particles with Gravity and Turbulance fields.
(For more explanation of particle,please refer to
Maya Tutorial:basics of particle) 
Make some splinter objects,
(in this example, I made 4 pieces of objects)
select all the objects and the particle in this order
Particle > Instancer(Replacement)
In this step, it seems that only one object is instanced to the particles.
Select particleShape and open the Attribute Editor.
Click General button in Add Dynamic Attributes.
The Add Attribute Window will open,
enter a variable name r_off in Attribute Name,
select Vector, Per Particle,
click Add button
Add Attributes r_spd and rot according to the same procedure as r_off.
Add index attribute with Data Type Float.
In Per Particle(Array) Attributes,
you can see the attibutes, index, rot, r_spd, r_off, are added.
Open the Expression Editor
(Window > Animation Editors > Expression Editor...)
Select Object Filter > Dynamics > Particle,
select particleShape
select Creation radio button (to make Creation Expression), enter expressions below
index = id%4;
r_off = <<rand(6.28),rand(6.28),rand(6.28)>>;
r_spd = <<rand(6.28),rand(6.28),rand(6.28)>>*1;
Click Creat button.
(index = id%4; 4 is number of objects
r_spd = <<rand(6.28),rand(6.28),rand(6.28)>>*1; 1 is multiple of rotation
6.28 is one rotation for the unit of the radian
rand(6.28) a random floating point number between 0 and 6.28)
Select Runtime before Dynamics radio button (to make Runtime Expression), enter expressions below
rot = r_off + r_spd * age;
Click Creat button.
Select particleShape, open the Attribute Editor,
in instancer tab, set Rotation Angle Units to Radians
In particleShape tab
set ObjectIndex to index, set Rotation to rot
Completed.
discuss this topic to forum
