three.js鼠標控制物體旋轉

當咱們須要固定場景背景，固定攝像機的時候。移動旋轉物體可使用Three.js提供的OrbitControls.js，也能夠手動寫控制器。

原理：獲取鼠標點擊的位置與移動的距離，根據移動的距離計算出大概旋轉的角度。

查看旋轉效果

<script src="../dist/js/three.js"></script>
    <script src="../dist/js/Projector.js"></script>
    <script src="../dist/js/CanvasRenderer.js"></script>

<script>
    var container;
    var camera, scene, renderer;
    var cube, plane;
    var width, height;

    var targetRotation = 0;
    var targetRotationOnMouseDown = 0;

    var mouseX = 0;
    var mouseXOnMouseDown = 0;

    var windowHalfX = window.innerWidth / 2;
    var windowHalfY = window.innerHeight / 2;
    console.log(window.innerHeight)
    init();
    animate();

    function init() {
        container = document.getElementById('canvasWrap')
        width = document.getElementById('canvasWrap').clientWidth;
        height = document.getElementById('canvasWrap').clientHeight;
        camera = new THREE.PerspectiveCamera(70, width / height, 1, 1000);
        camera.position.y = 150;
        camera.position.z = 500;

        scene = new THREE.Scene();
        scene.background = new THREE.Color(0xf0f0f0);

        //cube
        var geometry = new THREE.BoxGeometry(200, 200, 200);
        //console.log(geometry.faces.length) //12   一個面有2個三角面片
        for (var i = 0; i < geometry.faces.length; i += 2) {
            var hex = Math.random() * 0xffffff;
            geometry.faces[i].color.setHex(hex);
            geometry.faces[i + 1].color.setHex(hex)

        }
        //vertexColors:THREE.FaceColors  頂點顏色採用上面循環中建立的3角面片的顏色（立方體顯示的顏色就是三角面片的顏色）
        //overdraw:0.5 設置的目的避免相鄰的2個三角面片有分隔線,至關於重疊部分爲0.5
        var material = new THREE.MeshBasicMaterial({ vertexColors: THREE.FaceColors, overdraw: 0.5 }); //
        cube = new THREE.Mesh(geometry, material);
        cube.position.y = 150; //position(0,150,0)
        scene.add(cube);

        //plane
        var geometry = new THREE.PlaneBufferGeometry(200, 200);
        geometry.rotateX(-Math.PI / 2); //從右邊看順時針旋轉
        var material = new THREE.MeshBasicMaterial({ color: 0xe0e0e0, overdraw: 0.5 });
        plane = new THREE.Mesh(geometry, material);
        scene.add(plane);

        //CanvasRenderer 有更好的兼容性
        renderer = new THREE.CanvasRenderer();
        renderer.setPixelRatio(window.devicePixelRatio);
        renderer.setSize(width, height);
        container.appendChild(renderer.domElement);

        document.addEventListener("mousedown", onDocumentMouseDown, false);
        document.addEventListener("touchstart", onDocumentTouchStart, false);
        document.addEventListener("touchmove", onDocumentTouchMove, false);

        window.addEventListener("resize", onWindowResize, false);
    }

    function onWindowResize() {
        windwoHalfX = width / 2;
        windwoHalfY = height / 2;
        camera.aspect = width / height;
        camera.updateProjectionMatrix();

        renderer.setSize(width, height);
    }

    function onDocumentMouseDown(event) {
        event.preventDefault();
        document.addEventListener("mousemove", onDocumentMouseMove, false);
        document.addEventListener("mouseup", onDocumentMouseUp, false);
        document.addEventListener("mouseout", onDocumentMouseOut, false);
        //按下去的時候鼠標相對位置
        mouseXOnMouseDown = event.layerX - windowHalfX;
        //鼠標按下的旋轉角度
        targetRotationOnMouseDown = targetRotation;
    }

    function onDocumentMouseMove(event) {
        //移動的時候鼠標相對位置
        mouseX = event.layerX - windowHalfX;
        //移動的時候旋轉的角度 = 剛按下鼠標的角度+移動的位置-鼠標按下時的位置
        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 onDocumentTouchStart(event) {
        if (event.touches.length === 1) {
            event.preventaDefault();
            mouseXOnMouseDown = event.touches[0].layerX - windowHalfX;
            targetRotationMouseDown = targetRotation;
        }
    }

    function onDocumentTouchMove(event) {
        if (event.touches.length === 1) {
            event.preventaDefault();
            mouseX = event.touches[0].layerX - windowHalfX;
            targetRotation = targetRotationOnMouseDown + (mouseX - mouseXOnMouseDown) * 0.05;;
        }
    }

    function animate() {
        requestAnimationFrame(animate);
        render();
    }

    function render() {
        // cube.rotation.y 初始值爲0
        plane.rotation.y = cube.rotation.y += (targetRotation - cube.rotation.y) * 0.05;
        renderer.render(scene, camera);

    }
    </script>