mat4.multiply(mvMatrix, cameraRotationMat);

var mouseDown = false;
var prevMouseX = null;
var prevMouseY = null;

var cameraRotationMat = mat4.create();
mat4.identity(cameraRotationMat);

function handleMouseDown(event){
    mouseDown = true;
    prevMouseX = event.clientX;
    prevMouseY = event.clientY;
}

function handleMouseUp(event){
    mouseDown = false;
}


function handleMouseMove(event){
    if (!mouseDown){
        return;
    }

    var currentX = event.clientX;
    var currentY = event.clientY;
    var deltaX = currentX - prevMouseX;
    var newRotationMatrix = mat4.create();

    mat4.identity(newRotationMatrix);
    mat4.rotate(newRotationMatrix, degToRad(deltaX/10), [0, 1, 0]);

    var deltaY = currentY-prevMouseY;
    mat4.rotate(newRotationMatrix, degToRad(deltaY/10), [1, 0, 0]);

    mat4.multiply(newRotationMatrix, cameraRotationMat,cameraRotationMat);

    prevMouseX = currentX;
    prevMouseY = currentY;

}