本篇我们来介绍 ShapeGeometry 几何体。通过前两篇的介绍,我们会发现 PlaneGeometry 和 CircleGeometry 都只有有限的方法来定制他们的外观。如果我们想创建一个自定义的二维图形,那么就只能依靠今天要讲的 ShapeGeometry 了。
为了使用 ShapeGeometry,我们首先需要通过 THREE.Shape 创建一个自定义的基本形状,然后把它作为参数传递给 ShapeGeometry 构造函数。因此,我们先来看看如何使用 THREE.Shape 创建自定义的基本形状,代码片段如下:
function drawShape() {
var shape = new THREE.Shape();
shape.moveTo(10, 10); // moveTo( x, y )
shape.lineTo(10, 40); // lineTo( x, y ) - 线
shape.bezierCurveTo(15, 25, 25, 25, 30, 40); // bezierCurveTo( cp1X, cp1Y, cp2X, cp2Y, x, y ) - 贝塞尔曲线
shape.splineThru([
new THREE.Vector2(32, 30),
new THREE.Vector2(28, 20),
new THREE.Vector2(30, 10)
]); // splineThru ( vector2Array ) - 样条线
shape.quadraticCurveTo(20, 15, 10, 10); // quadraticCurveTo( cpX, cpY, x, y ) - 二次曲线
var hole = new THREE.Path(); // 添加“眼睛”孔洞1
hole.absellipse(16, 24, 2, 3, 0, Math.PI * 2, false);
shape.holes.push(hole);
hole = new THREE.Path(); // 添加“眼睛”孔洞2
hole.absellipse(23, 24, 2, 3, 0, Math.PI * 2, false);
shape.holes.push(hole);
hole = new THREE.Path(); // 添加“嘴巴”孔洞
hole.absarc(20, 16, 2, 0, Math.PI, false);
shape.holes.push(hole);
return shape;
}
在这段代码里,你可以看到我们用线段(line)、曲线(curve)和样条线(spline)创建出图像的轮廓,然后用 THREE.Shape 类的 holes(孔洞)属性添加了几个洞(两只眼睛,一张嘴巴)。下表列出了 THREE.Shape 类用来创建图形的绘图函数:
函数名 | 描述 |
---|---|
moveTo(x, y) | 将绘图点移动到指定的 x、y 座标处 |
lineTo(x, y) | 从当前位置(例如 moveTo 设定的位置)画一条线到指定的 x、y 座标处 |
quadricCurveTo(cpx, cpy, x, y) (二次曲线) |
此函数为二次曲线。你可以使用两种方法来画曲线:quadricCurveTo 或者 bezierCurveTo。这两种曲线的不同之处在于指定曲线曲率的方法不一样,如下图所示: 对于三次曲线,除了指定结束点(x, y)外,还需要额外指定两个点(cpx1, cpy1, cpx2, cpy2)来控制曲线的曲率。 |
bezierCurveTo(cpx1, cpy1, cpx2, cpy2, x, y) (贝塞尔曲线) |
此函数为三次曲线。相关说明参考上一行的二次曲线。 |
splineThru(vector2Array) | 此函数沿着参数指定的座标集合绘制一条光滑的样条曲线。其参数为一个 THREE.Vector2 对象数组。 |
arc(x, y, radius, startAngle, endAngle, clockwise) | 次函数绘制一个圆或者一段弧。x, y 用来指定圆心与当前位置的偏移量。radius 设定圆的大小。而 startAngle 及 endAngle 则用来定义圆弧要画多长。布尔属性 clockwise 决定这段弧是顺时针画还是逆时针画。 |
absArc(x, y, radius, startAngle, endAngle, clockwise) | 参考 arc 函数。只不过其指定的圆心位置是绝对位置,而不是相对当前位置的偏移量。 |
ellipse(x, y, radiusX, radiusY, startAngle, endAngle, clockwise) | 参考 arc 函数。只是椭圆可以分别指定 x 轴半径及 y 轴半径。 |
absEllipse(x, y, radiusX, radiusY, startAngle, endAngle, clockwise) | 参考 ellipse 函数。只不过其指定的圆心位置是绝对位置,而不是相对当前位置的偏移量。 |
在继续讨论之前,我们先给出一个完整的示例,代码如下:
<!DOCTYPE html>
<html>
<head>
<title>示例 05.03 - ShapeGeometry</title>
<script src="../build/three.js"></script>
<script src="../build/js/controls/OrbitControls.js"></script>
<script src="../build/js/libs/stats.min.js"></script>
<script src="../build/js/libs/dat.gui.min.js"></script>
<script src="../jquery/jquery-3.2.1.min.js"></script>
<style>
body {
/* 设置 margin 为 0,并且 overflow 为 hidden,来完成页面样式 */
margin: 0;
overflow: hidden;
}
/* 统计对象的样式 */
#Stats-output {
position: absolute;
left: 0px;
top: 0px;
}
</style>
</head>
<body>
<!-- 用于 WebGL 输出的 Div -->
<div id="webgl-output"></div>
<!-- 用于统计 FPS 输出的 Div -->
<div id="stats-output"></div>
<!-- 运行 Three.js 示例的 Javascript 代码 -->
<script type="text/javascript">
var scene;
var camera;
var render;
var webglRender;
//var canvasRender;
var controls;
var stats;
var guiParams;
var ground;
//var cube;
//var sphere;
var plane;
var meshMaterial;
var ambientLight;
var spotLight;
//var cameraHelper;
$(function() {
stats = initStats();
scene = new THREE.Scene();
webglRender = new THREE.WebGLRenderer( {antialias: true, alpha: true} ); // antialias 抗锯齿
webglRender.setSize(window.innerWidth, window.innerHeight);
webglRender.setClearColor(0xeeeeee, 1.0);
webglRender.shadowMap.enabled = true; // 允许阴影投射
render = webglRender;
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 30, 1000); // 2147483647
camera.position.set(-45.5, 68.2, 90.9);
var target = new THREE.Vector3(10, 0 , 0);
controls = new THREE.OrbitControls(camera, render.domElement);
controls.target = target;
camera.lookAt(target);
$('#webgl-output')[0].appendChild(render.domElement);
window.addEventListener('resize', onWindowResize, false);
ambientLight = new THREE.AmbientLight(0x0c0c0c);
scene.add(ambientLight);
spotLight = new THREE.SpotLight(0xffffff);
spotLight.position.set(0, 30, 60);
spotLight.castShadow = true;
scene.add(spotLight);
//cameraHelper = new THREE.CameraHelper(spotLight.shadow.camera);
//scene.add(cameraHelper);
// 加入一个地面
var groundGeometry = new THREE.PlaneGeometry(100, 100, 4, 4);
var groundMaterial = new THREE.MeshBasicMaterial({color: 0x777777});
ground = new THREE.Mesh(groundGeometry, groundMaterial);
ground.rotation.set(-0.5 * Math.PI, 0, 0); // 沿着 X轴旋转-90°
scene.add(ground);
// 定义 shape
var shape = drawShape();
// 材质
meshMaterial = [
new THREE.MeshNormalMaterial({side: THREE.DoubleSide}),
new THREE.MeshBasicMaterial({wireframe: true})
];
/** 用来保存那些需要修改的变量 */
guiParams = new function() {
this.rotationSpeed = 0.02;
this.addMesh = function() {
createMesh(shape);
};
this.addPoints = function() {
createLine(shape, false);
};
this.addSpacedPoints = function() {
createLine(shape, true);
};
}
/** 定义 dat.GUI 对象,并绑定 guiParams 的几个属性 */
var gui = new dat.GUI();
gui.add(guiParams, 'addMesh');
gui.add(guiParams, 'addPoints');
gui.add(guiParams, 'addSpacedPoints');
guiParams.addMesh();
renderScene();
});
/** 渲染场景 */
function renderScene() {
stats.update();
rotateMesh(); // 旋转物体
requestAnimationFrame(renderScene);
render.render(scene, camera);
}
/** 初始化 stats 统计对象 */
function initStats() {
stats = new Stats();
stats.setMode(0); // 0 为监测 FPS;1 为监测渲染时间
$('#stats-output').append(stats.domElement);
return stats;
}
/** 当浏览器窗口大小变化时触发 */
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
render.setSize(window.innerWidth, window.innerHeight);
}
/** 旋转物体 */
var step = 0;
function rotateMesh() {
step += guiParams.rotationSpeed;
scene.traverse(function(mesh) {
if ((mesh instanceof THREE.Mesh || mesh instanceof THREE.Line) && mesh != ground) {
//mesh.rotation.x = step;
mesh.rotation.y = step;
//mesh.rotation.z = step;
}
});
}
function drawShape() {
var shape = new THREE.Shape();
shape.moveTo(10, 10); // moveTo( x, y )
shape.lineTo(10, 40); // lineTo( x, y ) - 线
shape.bezierCurveTo(15, 25, 25, 25, 30, 40); // bezierCurveTo( cp1X, cp1Y, cp2X, cp2Y, x, y ) - 贝塞尔曲线
shape.splineThru([
new THREE.Vector2(32, 30),
new THREE.Vector2(28, 20),
new THREE.Vector2(30, 10)
]); // splineThru ( vector2Array ) - 样条线
shape.quadraticCurveTo(20, 15, 10, 10); // quadraticCurveTo( cpX, cpY, x, y ) - 二次曲线
var hole = new THREE.Path(); // 添加“眼睛”孔洞1
hole.absellipse(16, 24, 2, 3, 0, Math.PI * 2, false);
shape.holes.push(hole);
hole = new THREE.Path(); // 添加“眼睛”孔洞2
hole.absellipse(23, 24, 2, 3, 0, Math.PI * 2, false);
shape.holes.push(hole);
hole = new THREE.Path(); // 添加“嘴巴”孔洞
hole.absarc(20, 16, 2, 0, Math.PI, false);
shape.holes.push(hole);
return shape;
}
function createMesh(shape) {
scene.remove(plane);
var shapeGeometry = new THREE.ShapeGeometry(shape);
plane = new THREE.SceneUtils.createMultiMaterialObject(shapeGeometry, meshMaterial);
plane.castShadow = true;
plane.position.set(0, 0, 0);
scene.add(plane);
}
/** 从已有的 shape 中进行分段再得出新形状 */
function createLine(shape, spaced) {
scene.remove(plane);
var newPoints;
var shapeGeometry;
if (spaced) {
newPoints = shape.getSpacedPoints(3); // 把整个 shape 路径当做一个整体进行分段并得到一个点集
} else {
newPoints = shape.getPoints(10); // 分别把 shape 中的每一段路径进行分段(此处为 10 段)并得到一个点集
}
shapeGeometry = new THREE.Geometry();
newPoints.forEach(function(vec2){
shapeGeometry.vertices.push(new THREE.Vector3(vec2.x, vec2.y, 0));
});
plane = new THREE.Line(shapeGeometry, new THREE.LineBasicMaterial({color: 0xff3333,linewidth: 2}));
plane.castShadow = true;
plane.position.set(0, 0, 0);
scene.add(plane);
}
</script>
</body>
</html>
这个示例的效果如下所示:
函数 | 描述 |
---|---|
getPoints( divisions ) | 此函数将图形转换成一个点集。参数 divisions(分段数)定义返回点的数目,它会分别应用到 shape 路径的每一个部分。 |
getSpacedPoints( divisions ) | 此函数也是将图形转换成一个点集。参数 divisions(分段数)定义返回点的数目,它会一次性应用到 shape 的整个路径上。 |
shapeGeometry = new THREE.Geometry();
newPoints.forEach(function(vec2){
shapeGeometry.vertices.push(new THREE.Vector3(vec2.x, vec2.y, 0));
});
plane = new THREE.Line(shapeGeometry, new THREE.LineBasicMaterial({color: 0xff3333,linewidth: 2}));
未完待续···