PhysicsJS -如何旋转元素以查看鼠标位置

Question

我试图旋转一个矩形，使其始终指向鼠标位置。

我试过这个：

document.getElementById('viewport').onmousemove = function(e){

     var scratch = Physics.scratchpad();
     mousePos = scratch.vector().set(e.x, e.y);

    var newAngle = box.state.pos.angle(mousePos);
    box.state.angular.pos = newAngle;

    scratch.done();
};

谢谢。

Answer 1

也许可以试试这样的方法：

document.getElementById('viewport').onmousemove = function(e){

    var scratch = Physics.scratchpad();
    // assuming your viewport is the whole screen
    mousePos = scratch.vector().set(e.pageX, e.pageY); 
    mousePos.vsub( box.state.pos ); // get vector pointing towards mouse pos

    var newAngle = mousePos.angle(); // get angle with respect to x axis
    box.state.angular.pos = newAngle;

    scratch.done();
};