1. import peasy.org.apache.commons.math.*;
   import peasy.*;
   import peasy.org.apache.commons.math.geometry.*;
2. import processing.opengl.*;
3. import unlekker.util.*;
   import unlekker.geom.*;
   import unlekker.data.*;
7. // 2-dimensional array of 3D vector objects to contain our mesh
   Vec3 mesh[][];
8. // num will decide the mesh dimensions
   int numX;
   int numY;
9. // use the CTRL key for interface
   boolean ctrlDown=false;
10. // translation the Z direction
    float xUnit, yUnit, zTrans;
    float rotX, rotY, amplitude;
11. PImage extrude;
    int[][] values;
14. 
    void setup() {
      size(1200, 1000, OPENGL);
15.   // allocate space for the mesh and fill it with empty vectors 
      numX=200;
      numY=200;
      mesh=new Vec3[numX][numY];
      meshPlane();
16.   xUnit=width/(float)numX;
      yUnit=height/(float)numY;
17.   rotX=30;
      rotY=0;
      amplitude=200;
      zTrans=-width/2;
18. 
      extrude = loadImage("ystone08.jpg");
      extrude.loadPixels();
      values = new int[extrude.width][extrude.height];
      for (int y = 0; y < extrude.height; y++) {
        for (int x = 0; x < extrude.width; x++) {
          color pixel = extrude.get(x, y);
          values[x][y] = int(brightness(pixel));
        }
      }
    }
19. void draw() {
      background(0);
21. 
      // translate to center of screen and use mouse movement
      // to rotate the scene
      translate(width/2, height/2, zTrans);
      rotateX(rotX);
      rotateY(rotY);
22. 
      stroke(255, 255, 255, 50);
      noFill();
      drawMesh();
    }
24. 
    void keyPressed() {
26. 
      // check for CTRL key
      if (key == CODED && keyCode==CONTROL) {
        ctrlDown=true;
        println("ctrlDown "+ctrlDown);
      }
    }
27. void keyReleased() {
      // check for CTRL key to see if it has been released
      if (key == CODED && keyCode==CONTROL) {
        ctrlDown=false;
      }
    }
    
32. 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;
      }
    }
    
34. 
    // drawMesh is a custom method that takes care of drawing the
    // mesh using beginShape() / endShape()
    void drawMesh() {
35.   for (int i=0; i<numX-1; i++) {
        beginShape(QUAD_STRIP);
        for (int j=0; j<numY; 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();
      }
    }
36. // sets the mesh to an even grid plane
    void meshPlane() {
37.   for (int y = 0; y < extrude.width-1; y++) {
        for (int x = 0; x < extrude.height-1; x++) {
      
              mesh[y][x]=new Vec3((x-numX/2)*10, 0, (-values[x][y]));
        }
      }
        }