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<head>
    <meta charset="UTF-8">
    <title>three.js从入门到精通系列教程048 - 创建粒子模拟下雨雨滴效果</title>
    <script src="ThreeJS/three.js"></script>
    <script src="ThreeJS/jquery.js"></script>
</head>

<body>
    <script>
        var myRenderer, myCamera, myScene, myPoints;
        //创建渲染器
        function initRender() {
            myRenderer = new THREE.WebGLRenderer({ antialias: true });
            myRenderer.setClearColor(new THREE.Color(0xffffff));
            myRenderer.setSize(window.innerWidth, window.innerHeight);
            document.body.appendChild(myRenderer.domElement);
            myCamera = new THREE.PerspectiveCamera(45,
                window.innerWidth / window.innerHeight, 1, 200);
            myCamera.position.set(0, 20, 100);
            myCamera.lookAt(new THREE.Vector3(0, 30, 0));
            myScene = new THREE.Scene();
        }
        //创建粒子(雨滴)
        function createParticles(size, transparent, opacity,
            vertexColors, sizeAttenuation, color) {
            var myTexture = new THREE.TextureLoader().load("images/img057.png");
            var myGeometry = new THREE.Geometry();
            var myMaterial = new THREE.PointsMaterial({
                size: size, transparent: transparent, opacity: opacity,
                vertexColors: vertexColors, sizeAttenuation: sizeAttenuation,
                color: color, map: myTexture, depthTest: false
            });
            var myRange = 120 * 3;
            for (var i = 0; i < 9500; i++) {
                var myPoint = new THREE.Vector3(Math.random() * myRange - myRange / 2,
                    Math.random() * myRange - myRange / 2, Math.random() * myRange - myRange / 2);
                myPoint.velocityY = 0.1 + Math.random() / 5;
                myPoint.velocityX = (Math.random() - 0.5) / 3;
                myGeometry.vertices.push(myPoint);
                var myColor = new THREE.Color(0xffffff);
                myGeometry.colors.push(myColor);
            }
            myPoints = new THREE.Points(myGeometry, myMaterial);
            myScene.add(myPoints);
        }
        //渲染粒子(雨滴)
        function animate() {
            var myVertices = myPoints.geometry.vertices;
            //实现雨滴下落动画
            myVertices.forEach(function (v) {
                v.y = v.y - (v.velocityY) * 3;
                v.x = v.x - (v.velocityX) * .5;
                if (v.y <= -60) v.y = 60;
                if (v.x <= -120 || v.x >= 120) v.velocityX = v.velocityX * -1;
            });
            //实时更新雨滴位置信息
            myPoints.geometry.verticesNeedUpdate = true;
            myRenderer.render(myScene, myCamera);
            requestAnimationFrame(animate);
        }
        initRender();
        createParticles(6, true, 0.8, true, true, 0xffffff);
        animate();
    </script>
</body>

</html>

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