Next to make an particleinstancer.Select all the polygen letters in the outline window( note: dont select the group), creat particle instancer.In the option window, turn on "Allow All data types".select the "objectindex" to the new attribute "index".



Now you will see all the particles in the scene turned int letter "a". we are going to add
an expressions to make each of the particles to instance one random letter.

Select particleshape1 and open the expression editor.Add the runtime expression

index=rand(1,26);

Play the animtion and you will find that each particles are now instancing a random letter and changes every frame. It is now near the effect we want. But we still need to write some expressions to control the motion of each particle.


Select particleshape1 and add one another array attribute "gate". It has not much meaning , just for used in the expression. Add the runtime expressions below to the particleshape1.

particleShape1.index=rand(1,26);
vector $temp=particleShape1.worldVelocity;
if ($temp.y<=rand(-10,-5))
{ particleShape1.gate=1;};
if ($temp.y>=(-1))
{particleShape1.gate=0;};

if (particleShape1.gate==1){ particleShape1.acceleration=<<0,rand(20,25),0>>;
//print("aaaa");
};
if (particleShape1.gate==0) {
particleShape1.acceleration=<<0,rand(-25,-20),0>>;
//print("bbbb");
};

These expressions is to control the acceleration of each particles along the y axis. Play the animation and you can now get a cool random acceleratoin effect for the particles;

Finally you need to position your camera and do render. I rendered the front camera. I think it looks good. When done, you can use Maya fusion or some other software to add some motion blur or tail effects. Here is a picture of my last effect.



At last, you can change the expressions to get some other special effects. All is you imagine. Have Fun

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Harley Zhao

Original Force Animation Studio

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