//     UP key    move up
//     DOWN key  move down
//     LEFT key  strafe left
//     RIGHT key strafe left

//
float movefactor = 8.0;
PVector  cameraPostion, cameraTarget, cameraDirection, purpDirection;

float c = cos(PI/2);
float s = sin(PI/2);
float [] m1 = {1,0,0.01,   0,1,0,   -0.01,0,1}  ;// pi/64  .... 3 degress anti clock wize rotation
float [] m2 = {1,0,-0.01,  0,1,0,    0.01,0,1}  ;// pi/64  .... 3 degress clock wize rotation
float [] m3 = {0,0,1      ,0,1,0,      -1,0,0}  ;// pi/2  .... 90 degress anti clock wize rotation

void setup() {
  size(800,600, P3D);
  orientation(LANDSCAPE); 
 
  cameraPostion = new PVector(0, 0, 1000);  
  cameraTarget = new PVector(0.0, 0.0, 0.0); 
  cameraDirection = new PVector(0, 0, -1); 
  purpDirection = new PVector(0, 0, 0);

   // Update Look At Position. otherwize text will start at 0,0,0 then jump to cam target on key press
   cameraTarget = PVector.add(cameraPostion, cameraDirection);
} 
 void draw() {
  background(0);
  lights();
  ambient(250, 250, 250);
 

camera(cameraPostion.x,   cameraPostion.y,   cameraPostion.z,
       cameraTarget.x,    cameraTarget.y,    cameraTarget.z,
       0.0, 1.0, 0.0);

 fill(0,0,255);    
 box (70);
 
text(" HELLO World! ",cameraTarget.x,cameraTarget.y,cameraTarget.z-100);

 }

 void keyPressed()
 {
  
    if (key == CODED) {
   
    // Move Up.
    if (keyCode == UP)    { cameraPostion.y -= movefactor;  }
   
    // Move Down.
    if (keyCode == DOWN)  { cameraPostion.y  += movefactor; }
   
    // Strife Left.
    if (keyCode == LEFT)
    {    
    purpDirection.x = (m3[0]*cameraDirection.x)+(m3[1]*cameraDirection.y)+(m3[2]*cameraDirection.z);
    purpDirection.y = (m3[3]*cameraDirection.x)+(m3[4]*cameraDirection.y)+(m3[5]*cameraDirection.z);
    purpDirection.z = (m3[6]*cameraDirection.x)+(m3[7]*cameraDirection.y)+(m3[8]*cameraDirection.z);
    cameraPostion = PVector.add(cameraPostion,(PVector.mult(purpDirection,movefactor)));  
    }
   
    // Strife Right.
    if (keyCode == RIGHT)
    {
    purpDirection.x = (m3[0]*cameraDirection.x)+(m3[1]*cameraDirection.y)+(m3[2]*cameraDirection.z);
    purpDirection.y = (m3[3]*cameraDirection.x)+(m3[4]*cameraDirection.y)+(m3[5]*cameraDirection.z);
    purpDirection.z = (m3[6]*cameraDirection.x)+(m3[7]*cameraDirection.y)+(m3[8]*cameraDirection.z);
    cameraPostion = PVector.sub(cameraPostion,(PVector.mult(purpDirection,movefactor))); 
    }   
 }

    // Rotate Left.  
   if (key == 'q' || key == 'Q' )
   {  
   cameraDirection.x = (m1[0]*cameraDirection.x)+(m1[1]*cameraDirection.y)+(m1[2]*cameraDirection.z);
   cameraDirection.y = (m1[3]*cameraDirection.x)+(m1[4]*cameraDirection.y)+(m1[5]*cameraDirection.z);
   cameraDirection.z = (m1[6]*cameraDirection.x)+(m1[7]*cameraDirection.y)+(m1[8]*cameraDirection.z);
 }
  
   // Rotate Right.
   if (key == 'e' || key == 'E'  )
   { 
    cameraDirection.x = (m2[0]*cameraDirection.x)+(m2[1]*cameraDirection.y)+(m2[2]*cameraDirection.z);
    cameraDirection.y = (m2[3]*cameraDirection.x)+(m2[4]*cameraDirection.y)+(m2[5]*cameraDirection.z);
    cameraDirection.z = (m2[6]*cameraDirection.x)+(m2[7]*cameraDirection.y)+(m2[8]*cameraDirection.z);
   }
  
   // Move Forward.
   if (key == 's' || key == 'S' ) { cameraPostion = PVector.sub(cameraPostion,(PVector.mult(cameraDirection,movefactor)));  }
  
   // Move Backward.
   if (key == 'w' || key == 'W' ) { cameraPostion = PVector.add(cameraPostion,(PVector.mult(cameraDirection,movefactor)));   }
 
   // Update Look At Position.
   cameraTarget = PVector.add(cameraPostion, cameraDirection);
  
 }