so, i'm very, very new with processing and i need some pointers on a project i'm doing for class.  

my goal is to make a crowd using the same 8 images of figures over and over on a set Y coordinate with randomized Y and Z values.  I'm wanting the lesser Z values to be behind the greater ones so that the smaller figures are not overlapping the larger.

any help here?

and also...to add an element of time, I would potentially like to make the randomized figures advance forward and continue appearing randomly

int[] personX;
int[] personZ;

PImage[] images;

void setup()
{
 size(720, 480, P3D);
 images=new PImage[8];
 images[0]=loadImage("walker.1.pdf");
 images[1]=loadImage("walker.2.pdf");
 images[2]=loadImage("walker.3.pdf");
 images[3]=loadImage("walker.4.pdf");
 images[4]=loadImage("walker.5.pdf");
 images[5]=loadImage("walker.6.pdf");
 images[6]=loadImage("walker.7.pdf");
 images[7]=loadImage("walker.8.pdf");
 //load all images

 personX=new int[50]; //50 people
 personZ=new int[50];
 for(int i=0; i<50; i++)
 {
   personX[i]=int (random(720));
   personZ[i]=int (random(0));
 }
}

void draw()
{
 background(0);
 for(int i=0;i<50;i++)
 {
   pushMatrix();
   translate(personX[i],0,personZ[i]);
   image(images[i%8],0,0);
   popMatrix();
 }
}