hello
i have this code which you will se that there is a grid showing some perspective lines

i want to place in the area of this grid multiple boxes. Basically i would like to have different sizes of boxes placed randomnly within the grid or in  a sequence. but first i d like to get them

i have tried doing that using the function below:

fill(230);

//  
 for(int i = 0; i < 5; i++){
   translate(450,-i*10,70);
 box(10,20,20);
 }

But unfortunately tha boxes appear in sequence outside the grid.
i an new to this so i took existing codes from libraries as you wil be able to see and then modified them

import processing.opengl.*;

// unlekkerLib - Marius Watz, workshop.evolutionzone.com
//
// Example using a 2-dimensional array of 3D vectors to calculate
// a mesh.

import unlekker.util.*;
import unlekker.geom.*;
import unlekker.data.*;

// 2-dimensional array of 3D vector objects to contain our mesh
Vec3 mesh[][];

// num will decide the mesh dimensions
int num;  



// use the CTRL key for interface
boolean ctrlDown=false;

// translation the Z direction
float xUnit,yUnit, zTrans;
float rotX,rotY,amplitude;
float tx,ty,tz;

void setup() {
 size(800,600,OPENGL);

 // allocate space for the mesh and fill it with empty vectors  
 num=100;
 mesh=new Vec3[num][num];
 meshPlane();
 
 xUnit=width/(float)num;
 yUnit=height/(float)num;

 rotX=30;
 rotY=45;
 amplitude=100;
 zTrans=-width/2;
 
// add a MouseWheelListener so we can use the mouse wheel
 // to zoom with
 frame.addMouseWheelListener(new MouseWheelInput());
 
}

void draw() {
 background(0);



 lights();
 
 // translate to center of screen and use mouse movement
 // to rotate the scene
 translate(width/2,height/2,zTrans);
 rotateX(rotX);
 rotateY(rotY);

 
 stroke(255);
 fill(100,23,65, 44);  
 drawMesh();
 
//FOR PERSPECTIVE LINES
for(int i = 0; i < 25; i++){
   // a rectangleDraw
   line(-500, -50, -i*20,  500, -50, -i*20);
   line( 500, -50, -i*20,  500,  50, -i*20);
   line( 500,  50, -i*20, -500,  50, -i*20);
   line(-500,  50, -i*20, -500, -50, -i*20);
   
   
   
//    line(-500, -250, (i*20)+25,  500, -250, (i*20)+25);
//    line( 500, -250, (i*20)+25,  500,  250, (i*20)+25);
//    line( 500,  250, (i*20)+25, -500,  250, (i*20)+25);
//    line(-500,  250, (i*20)+25, -500, -250, (i*20)+25);
//
//    

   

}



fill(230);

//  
 for(int i = 0; i < 5; i++){
   translate(450,-i*10,70);
 box(10,20,20);
 }
 

 
 
 
 
}


void keyPressed() {
 

 
 if(key==CODED) {
   // check to see if CTRL is pressed

   if(keyEvent.isControlDown()) {
     // do zoom in the Z axis
     if(keyCode==UP) tz=tz+2;
     if(keyCode==DOWN) tz=tz-2;
   }
   // check to see if CTRL is pressed
   else if(keyEvent.isShiftDown()) {
     // do translations in X and Y axis
     if(keyCode==UP) ty=ty-2;
     if(keyCode==DOWN) ty=ty+2;
     if(keyCode==RIGHT) tx=tx+2;
     if(keyCode==LEFT) tx=tx-2;
   }
   else {
     // do rotations around X and Y axis
     if(keyCode==UP) rotX=rotX+radians(2);
     if(keyCode==DOWN) rotX=rotX-radians(2);
     if(keyCode==RIGHT) rotY=rotY+radians(2);
     if(keyCode==LEFT) rotY=rotY-radians(2);
   }
 }
}
// utility class to handle mouse wheel events
class MouseWheelInput implements MouseWheelListener{
 void mouseWheelMoved(MouseWheelEvent e) {
   int step=e.getWheelRotation();
   zTrans=zTrans+step*50;
 }
}

void mouseDragged() {
 // if CTRL key is down, then adjust amplitude
 if(ctrlDown) {
   amplitude=((float)mouseY/(float)height)*height;
   println("amplitude "+amplitude);
 }
 // else rotate the viewport
 else {
   rotX=((float)mouseX/(float)width)*2*PI;
   rotY=((float)mouseY/(float)height)*2*PI;
 }
//  
}

// drawMesh is a custom method that takes care of drawing the
// mesh using beginShape() / endShape()
void drawMesh() {

 for(int i=0; i<num-1; i++) {
   beginShape(QUAD_STRIP);
   for(int j=0; j<num; j++) {
     vertex(mesh[j][i].x,mesh[j][i].y * amplitude ,mesh[j][i].z);
     vertex(mesh[j][i+1].x,mesh[j][i+1].y  * amplitude, mesh[j][i+1].z);
   }
   endShape();    
 }
}

// sets the mesh to an even grid plane
void meshPlane() {
 for(int i=0; i<num; i++)
   for(int j=0; j<num; j++)
     mesh[i][j]=new Vec3((i-num/2)*10,0,(j-num/2)*10);
}

// sets the mesh data to a Perlin noisefield
void meshNoise() {
 float x,y,a,aD,b,bD,val;

 // initialize parameters for the noise field.
 // "a" is our position in the X direction of the noise.
 // "b" is our position in the X direction of the noise.
 // "aD" and "bD" are used to traverse the noise field.
 a=random(1000);
 b=random(1000);
 aD=1.0/random(50,150);
 bD=1.0/random(50,150);

 // set amplitude and noiseDetail for noise field
 noiseDetail((int)random(4,8),random(0.4,0.9));

 for(int i=0; i<num; i++)
   for(int j=0; j<num; j++) {

     // calculate height as a function of 2D noise
     val=(noise(a+aD*(float)i,b+bD*(float)j)-0.5)*2;

     x=((float)i-num/2)*xUnit;;
     y=((float)j-num/2)*yUnit;
     mesh[i][j].set(x,val,y);

   }
}




i would also like to have those lines on top going to the other end og the grid but i cannot figure out the calculation.

if anyone can help it ll be fantastic

thanks!