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threejs-project
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case-033.html

<!DOCTYPE html>
<html>
	<head>
		<title>Threejs实现镜头跟随物体移动效果，镜头拐弯并保持运动方向</title>
		<meta charset="UTF-8">
		<script type="text/javascript" src="libs/statistics.js"></script>
		<script type="text/javascript" src="libs/steak.js"></script>
		<script type="text/javascript" src="libs/three.js"></script>
		<script type="text/javascript" src="libs/OrbitControls.js"></script>
		<script type="text/javascript" src="libs/GLTFLoader.js"></script>
		<script type="text/javascript" src="libs/dat.gui.js"></script>
		<script type="text/javascript" charset="UTF-8" src="libs/Tween.min.js"></script>
		<style>
			body {
				margin: 0;
				overflow: hidden;
			}
		</style>
	</head>
	<body>
		<div id="dom"></div>
		<script type="text/javascript">
			var camera;
			var renderer;
			var mesh;
			var curve;
			var cube1;
			var cube2;

			function init() {
				// 创建一个场景，它将包含我们所有的元素，如物体，相机和灯光。
				var scene = new THREE.Scene();

				// 创建一个摄像机，它定义了我们正在看的地方
				camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 100000);
				// 将摄像机对准场景的中心
				camera.position.z = -5746;
				camera.position.y = 3289;
				camera.position.x = -15945;
				camera.lookAt(scene.position);
				var orbit = new THREE.OrbitControls(camera);

				// 创建一个渲染器并设置大小，WebGLRenderer将会使用电脑显卡来渲染场景
				renderer = new THREE.WebGLRenderer({
					antialias: true,
					logarithmicDepthBuffer: true,
				});
				renderer.setClearColor(new THREE.Color("#0e0934"));
				renderer.setSize(window.innerWidth, window.innerHeight);

				var ambientLight = new THREE.AmbientLight("#ffffff", 1);
				scene.add(ambientLight);

				// 将呈现器的输出添加到HTML元素
				document.getElementById("dom").appendChild(renderer.domElement);

				// 启动动画
				renderScene();
				initFeiji();

				function initFeiji() {
					var loader = new THREE.GLTFLoader();
					loader.load('assets/models/feiji/feiji.glb', function(result) {
						mesh = result.scene;
						mesh.position.set(-1000, -5000, -5000);
						scene.add(mesh);
						motion()
					});
				}

				function motion() {
					// 通过类CatmullRomCurve3创建一个3D样条曲线
					curve = new THREE.CatmullRomCurve3([
						new THREE.Vector3(-1000, -5000, -5000),
						new THREE.Vector3(1000, -5000, 0),
						new THREE.Vector3(1800, 800, 1000),
						new THREE.Vector3(800, 5000, 5000),
						new THREE.Vector3(0, 0, 10000)
					]);
					// 样条曲线均匀分割100
					var points = curve.getPoints(100);
					var geometry = new THREE.Geometry();
					// 把从曲线轨迹上获得的顶点坐标赋值给几何体
					geometry.vertices = points
					var material = new THREE.LineBasicMaterial({
						color: "#4488ff"
					});
					var line = new THREE.Line(geometry, material);
					scene.add(line);

					//管道体
					const tubeGeometry = new THREE.TubeGeometry(curve, 100, 500, 30); // 101取点数 3为r 30为三角切面数
					const tubeMesh = new THREE.Mesh(tubeGeometry, new THREE.MeshBasicMaterial({
						color: "#00aa00",
						side: THREE.DoubleSide,
						wireframe: true
					}))
					scene.add(tubeMesh)
				}

				function changeLookAt(t) {
					// 当前点在线条上的位置
					const position = curve.getPointAt(t);
					var nPos = new THREE.Vector3(position.x, position.y - 100, position.z);
					mesh.position.copy(nPos);
					// 返回点t在曲线上位置切线向量
					const tangent = curve.getTangentAt(t);
					// 位置向量和切线向量相加即为所需朝向的点向量
					const lookAtVec = tangent.add(nPos);
					mesh.lookAt(lookAtVec);

					if (t > 0.03) {
						var pos = curve.getPointAt(t - 0.03);
						camera.position.copy(pos);
						camera.lookAt(position)
					}
				}

				var clock = new THREE.Clock(); //声明一个时钟对象
				const loopTime = 10 * 1000; // loopTime: 循环一圈的时间
				let i = 0;

				function renderScene() {
					// 使用requestAnimationFrame函数进行渲染
					requestAnimationFrame(renderScene);
					renderer.render(scene, camera);

					if (curve) {
						let time = Date.now();
						let t = (time % loopTime) / loopTime; // 计算当前时间进度百分比
						setTimeout(function() {
							changeLookAt(t);
						}, 500)
					}
				}
			}
			window.onload = init;

			// 随着窗体的变化修改场景
			function onResize() {
				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();
				renderer.setSize(window.innerWidth, window.innerHeight);
			}
			// 监听窗体调整大小事件
			window.addEventListener('resize', onResize, false);
		</script>
	</body>
</html>