[help] goemetry shifted when toggling btw ortho() and perspective() in peasycam

I have the following code to toggle between orthogonal and perspective view of a 3D scene. However, in the orthogonal view the geometry is shifted away from the camera and scaled down. May I ask how to avoid this so that the camera remains focusing on the geometry located at the center of the display window in orthogonal view? Thanks!

import peasy.*; 
PeasyCam cam;
Boolean camOrtho = false; 

//////////////////////////////////////////////////////////
void setup(){
  size(1000, 1000, OPENGL);
  setupCamera();
}

//////////////////////////////////////////////////////////
void draw(){
  background(120); 

  updateCam();

  // draw stuff here ...       
  drawBbox();
}

//////////////////////////////////////////////////////////
void setupCamera () {
  hint(ENABLE_STROKE_PERSPECTIVE);
  float fov      = PI/3;  // field of view
  float nearClip = 1;
  float farClip  = 100000;
  float aspect   = float(width)/float(height);  
  perspective(fov, aspect, nearClip, farClip);  
  cam = new PeasyCam(this, 150); 
}

void updateCam () {
  if ( camOrtho == true ) {
    ortho();
  } else {
    //----- perspective -----
    float fov      = PI/3;  // field of view
    float nearClip = 1;
    float farClip  = 100000;
    float aspect   = float(width)/float(height);  
    perspective(fov, aspect, nearClip, farClip);
  }
}

void drawBbox () {
  stroke(0);
  noFill();
  box(100);
}

void keyPressed () {
  if ( key == 'o' ) { 
    camOrtho = (camOrtho == true) ? (false):(true);    
  }  
}