THREEJS的鼠标事件实现（中心旋转，放大缩小等）

最近使用threejs自带的TrackballControls.js或者OrbitControls.js发现一个问题：在场景中在一个平行光，当移动物体时，背面始终是黑的，因为没有光照，（本质就是因为使用自带的滚动求，移动的是相机，而不是移动物体）因为效果需要，自己写鼠标事件，控制物体（这样的好处是：当物体移到光照射到的地方，都能实现光亮的效果）

加一束平行光

var directionalLight = new THREE.DirectionalLight(0xFFFFFF);
directionalLight.intensity=1;
directionalLight.position.set( 0, 50,100 );
//把平行光加到场景中
scene.add( directionalLight );

效果图：可以看到，我旋转这个平面后，光照的地方就是一直都是亮的，没有光照的地方，是暗的

实现过程：

document.addEventListener( 'mousedown', onDocumentMouseDown, false );
document.addEventListener( 'mousewheel', onDocumentMouseWheel, false );//如果运行不出来，也不报错请检查大小写
document.addEventListener( 'touchstart', onDocumentTouchStart, false );
document.addEventListener( 'touchmove', onDocumentTouchMove, false );

function render() {
    //渲染场景和相机
    n1.rotation.y+= ( targetRotation - n1.rotation.y ) * 0.05;//n1就是旋转的整体
    renderer.render(scene, camera);

}

function onDocumentTouchMove( event ) {

    if ( event.touches.length == 1 ) {
        event.preventDefault();
        mouseX = event.touches[ 0 ].pageX - windowHalfX;
        targetRotation = targetRotationOnMouseDown + ( mouseX - mouseXOnMouseDown ) * 0.05;

    }

}
function onDocumentTouchStart( event ) {

    
    if ( event.touches.length === 1 ) {
        event.preventDefault();
        mouseXOnMouseDown = event.touches[ 0 ].pageX - windowHalfX;
        targetRotationOnMouseDown = targetRotation;
    }
}
function onDocumentMouseMove( event ) {

    //旋转
    mouseX = event.clientX - windowHalfX;
    mouseY = event.clientY - windowHalfY;
    targetRotation = targetRotationOnMouseDown + ( mouseX - mouseXOnMouseDown ) * 0.02;
   

}
function onDocumentMouseUp( event ) {

    document.removeEventListener( 'mousemove', onDocumentMouseMove, false );
    document.removeEventListener( 'mouseup', onDocumentMouseUp, false );
    document.removeEventListener( 'mouseout', onDocumentMouseOut, false );
}
function onDocumentMouseOut( event ) {

    document.removeEventListener( 'mousemove', onDocumentMouseMove, false );
    document.removeEventListener( 'mouseup', onDocumentMouseUp, false );
    document.removeEventListener( 'mouseout', onDocumentMouseOut, false );
}
function onDocumentMouseDown( event ) {

    event.preventDefault();
    document.addEventListener( 'mousemove', onDocumentMouseMove, false );
    document.addEventListener( 'mouseup', onDocumentMouseUp, false );
    document.addEventListener( 'mouseout', onDocumentMouseOut, false );

    mouseXOnMouseDown = event.clientX - windowHalfX;
    targetRotationOnMouseDown = targetRotation;

 

}

//放大缩小的功能实现，主要是通过鼠标的滚轮事件，改变的是carema的fov
function onDocumentMouseWheel(event){
    event.preventDefault();
    //event.stopPropagation();
      if (event.wheelDelta)
          {  //判断浏览器IE，谷歌滑轮事件
              if (event.wheelDelta > 0)
              {   //当滑轮向上滚动时
                  fov -= (near < fov ? 1 : 0);
              }
              else
              {   //当滑轮向下滚动时
                  fov += (fov < far ? 1 : 0);
              }
      }
      //console.info('camera.fov:'+camera.fov);
      //改变fov值，并更新场景的渲染
      camera.fov = fov;
      camera.updateProjectionMatrix();
      renderer.render(scene, camera);
}

注意：1.初始化camera

var  fov = 45,//拍摄距离  视野角值越大，场景中的物体越小
    near = 1,//最小范围
    far = 1000;//最大范围

camera = new THREE.PerspectiveCamera(fov, window.innerWidth / window.innerHeight, near, far);
camera.position.x = 0;
camera.position.y = 100;
camera.position.z =150;
camera.lookAt(new THREE.Vector3(0,0,0));

2，其他初始化

var targetRotation = 0;
var targetRotationOnMouseDown = 0;
var mouseX = 0,mouseY = 0;
var mouseXOnMouseDown = 0;
var windowHalfX = window.innerWidth / 2;
var windowHalfY = window.innerHeight / 2;