final float ZERO_X_ROT = PI - 0.4;
final float ZERO_Z_ROT = PI/2 + 0.4;

float xmag = ZERO_X_ROT, zmag = ZERO_Z_ROT;
float newXmag = ZERO_X_ROT, newZmag = ZERO_Z_ROT;
float rx,rz;

float xpos, ypos;
float px,py;

boolean rdragged = false, pdragged = false;


void beginCamera() {
  push();
  if (mousePressed) {
    if (keyPressed) {
      println("_"+key+"_");
      updateCameraPos();
    } else {
      updateCameraRot();
    }
  } else {
    xpos = width/2;
    ypos = height*0.9;
    newZmag = ZERO_X_ROT;
    newXmag = ZERO_Z_ROT;
    pdragged = false;
    rdragged = false;
  }

  float diff = xmag-newXmag;
  if (abs(diff) >  0.01)  xmag -= diff/4.0;
  diff = zmag-newZmag;
  if (abs(diff) >  0.01) zmag -= diff/4.0;

  translate(xpos, ypos, -10);

  rotateX(-xmag);
  rotateZ(-zmag);
  scale(8);
  ortho(-1,1,-1,1,-1,1);
}

void endCamera() {
  pop();
}

void updateCameraPos() {
  if (pdragged) {
    xpos = px - (pmouseX - mouseX);
    ypos = py - (pmouseY - mouseY);
    px = xpos;
    py = ypos;
  } else {
    px = xpos;
    py = ypos;
    pdragged = true;
  }
}

void updateCameraRot() {
  if (rdragged) {
    newXmag = rx - (pmouseY - mouseY)/float(height) * TWO_PI;
    newZmag = rz + (pmouseX - mouseX)/float(width) * TWO_PI;
    rx = newXmag;
    rz = newZmag;
  } else {
    rx = xmag;
    rz = zmag;
    rdragged = true;
  }

}