CS 464: Introduction to Computer Graphics

The following code rotates a viewdirection vector based on changes in the mouse:

// this code is called whenever the mouse moves
// Gangle is a global angle variable with the current view angle around the up
// vector of the Tank
 function handleMouseMove(event) {
    if (!mouseDown) { // only do things when mouse button down.
      return;
    }
    var newX = event.clientX;
    var newY = event.clientY;

    var deltaX = newX - lastMouseX;
    
    // get the adjust changing angle
    Gangle = Gangle + deltaX;


    // adjust the speed of the tank
    var deltaY = newY - lastMouseY;
    Gspeed = Gspeed - deltaY/1000000.0;

    lastMouseX = newX
    lastMouseY = newY;

// we have the latest angle, now lets rotate the viewdirection
    upVector = [0.0,1.0,0.0];  //we will just use Y as the up vector
    tankRotation = mat4.create();
    mat4.identity(tnakRotation);
    // create the rotation matrix
    mat4.rotate(tankRotation, -degToRad(Gangle), upVector);

    // ok now rotate the viewdirection by the current angle
    mat4.multiplyVec3(tankRotation, viewdirection);

    // so viewdirection now changes as the mouse is moved left and right.
    // if your code is using viewdirection in your genViewMatrix function
    // this will give you the ability to rotate your view.
    
  }

The following helper function degToRad() is useful for converting angles to Radians.

   function degToRad(degrees) 
   {
        return degrees * Math.PI / 180;
   }