three.js實現3D視野縮放效果

//照相機配置
 var fov = 40;//拍攝距離
 var near = 1;//最小范圍
 var far = 1000;//最大范圍
 var camera = new THREE.PerspectiveCamera(fov, window.innerWidth / window.innerHeight, near, far);

camera.fov = fov;//fov是變量哦 
camera.updateProjectionMatrix();
renderer.render(scene, camera);

canvas.addEventListener('mousewheel', mousewheel, false);
 //鼠標滑輪
 function mousewheel(e) {
 e.preventDefault();
 //e.stopPropagation();
 if (e.wheelDelta) { //判斷瀏覽器IE，谷歌滑輪事件
 if (e.wheelDelta > 0) { //當滑輪向上滾動時
 fov -= (near < fov ? 1 : 0);
 }
 if (e.wheelDelta < 0) { //當滑輪向下滾動時
 fov += (fov < far ? 1 : 0);
 }
 } else if (e.detail) { //Firefox滑輪事件
 if (e.detail > 0) { //當滑輪向上滾動時
 fov -= 1;
 }
 if (e.detail < 0) { //當滑輪向下滾動時
 fov += 1;
 }
 }
 camera.fov = fov;
 camera.updateProjectionMatrix();
 renderer.render(scene, camera);
 //updateinfo();
 }