用颜色填充线条之间的区域 - Three.js答案

【问题标题】：Fill Area between Lines with color - Three.js用颜色填充线条之间的区域 - Three.js
【发布时间】：2021-12-12 00:39:33
【问题描述】：

我有一系列线条，我需要用颜色为线条下方或线条之间的所有区域着色。

为了简单起见，我创建了一个带有闭合线的 sn-p。实际上，我有一个绘制多条线的程序（如股市图表），我需要为图表下方的所有区域着色。另请参阅屏幕截图。

如果我可能需要采取任何帮助甚至新方法，我将不胜感激。

<html>

<head>
    <title>My first three.js app</title>
    <style>
        body {
            margin: 0;
        }

        canvas {
            width: 100%;
            height: 100%
        }
    </style>
</head>

<body>
    <script src="https://threejs.org/build/three.min.js"></script>
    <script>
        var scene = new THREE.Scene();
        var camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 500);

        var renderer = new THREE.WebGLRenderer();
        renderer.setSize(window.innerWidth, window.innerHeight);
        document.body.appendChild(renderer.domElement);
        function createLine(startX,startY,endX,endY) {
            const geometry = new THREE.Geometry();
            geometry.vertices.push(new THREE.Vector3(startX, startY, 0));
            geometry.vertices.push(new THREE.Vector3(endX, endY, 0));
            const material = new THREE.LineBasicMaterial({
                color: 0xffffff
            });
            return new THREE.Line(geometry, material);
        }
        scene.add(createLine(0,0,1,0));
        scene.add(createLine(1,0,1,1));
        scene.add(createLine(1,1,0,1));
        scene.add(createLine(0,1,0,0));

        camera.position.z = 5;

        var animate = function () {
            requestAnimationFrame(animate);
            renderer.render(scene, camera);
        };

        animate();
    </script>
</body>

</html>

【问题讨论】：

我对 three.js 不太熟悉，但是为了给图表上色，我猜你需要画一个大的形状，而不是很多单独的线。还是我完全错了？
不知道。这就是问题所在。如果您尝试提出解决方案会很高兴:) 我当然可以用附加线“关闭”图表。这就是为什么我附上了简单的sn-p，它是4条闭合线。让事情变得简单。
作为一个选项，您可以使用THREE.PlaneGeometry() 并更改其上顶点。

标签： javascript three.js

【解决方案1】：

您可以使用THREE.Shape 和THREE.ShapeGeometry 绘制由THREE.Mesh 填充的多边形：

function createPolygon( poly ) {
    var shape = new THREE.Shape();
    shape.moveTo( poly[0][0], poly[0][1] );
    for (var i = 1; i < poly.length; ++ i)
        shape.lineTo( poly[i][0], poly[i][1] );
    shape.lineTo( poly[0][0], poly[0][1] );

    var geometry = new THREE.ShapeGeometry( shape );
    var material = new THREE.MeshBasicMaterial( {
        color: 0x800000
    } );
    return new THREE.Mesh(geometry, material);
}

var poly = [[0,1],[0.25,0],[0.5,0.5],[0.75,0],[1,1]];
scene.add(createPolygon(poly))

请参阅示例：

var renderer, scene, camera, controls;

init();
animate();

function createLine(startX,startY,endX,endY) {
    const geometry = new THREE.Geometry();
    geometry.vertices.push(new THREE.Vector3(startX, startY, 0));
    geometry.vertices.push(new THREE.Vector3(endX, endY, 0));
    const material = new THREE.LineBasicMaterial({
        color: 0xffffff
    });
    return new THREE.Line(geometry, material);
}

function createPolygon( poly ) {
  var shape = new THREE.Shape();
  shape.moveTo( poly[0][0], poly[0][1] );
  for (var i = 1; i < poly.length; ++ i)
    shape.lineTo( poly[i][0], poly[i][1] );
  shape.lineTo( poly[0][0], poly[0][1] );
    
  var geometry = new THREE.ShapeGeometry( shape );
    var material = new THREE.MeshBasicMaterial( {
        color: 0x800000
    } );
    return new THREE.Mesh(geometry, material);
}

function init() {

    // renderer
    renderer = new THREE.WebGLRenderer();
    renderer.setSize( window.innerWidth, window.innerHeight );
    document.body.appendChild( renderer.domElement );

    scene = new THREE.Scene();
    
    camera = new THREE.PerspectiveCamera( 40, window.innerWidth / window.innerHeight, 1, 1000 );
    //camera.position.set( 20, 20, 20 );
    camera.position.z = 5;
    window.onresize = resize;

    var light = new THREE.HemisphereLight( 0xeeeeee, 0x888888, 1 );
      light.position.set( 0, 20, 0 );
      scene.add( light );
    
    var poly = [[0,1],[0.25,0],[0.5,0.5],[0.75,0],[1,1]];
    
    scene.add(createPolygon(poly))
    
    for (var i = 0; i < poly.length-1; ++i)
    {
        var i2 = i<poly.length-1 ? i+1 : 0 
        scene.add(createLine(poly[i][0],poly[i][1],poly[i2][0],poly[i2][1]));
    }
}

function resize() {
    
    var aspect = window.innerWidth / window.innerHeight;
    renderer.setSize(window.innerWidth, window.innerHeight);
    camera.aspect = aspect;
    camera.updateProjectionMatrix();
}

function animate() {
    requestAnimationFrame( animate );
    renderer.render( scene, camera );
}

body {
    margin: 0;
}

canvas {
    width: 100%;
    height: 100%
}

&lt;script src="https://cdn.jsdelivr.net/npm/three@0.124/build/three.js"&gt;&lt;/script&gt;

【讨论】：

【解决方案2】：

要用颜色填充它，您必须使用带有面的几何图形 (THREE.Face3())。要获得它，您需要对形状进行三边形调整或使用适合您需要的现有几何图形，并对其顶点进行一些更改。

下面有一个非常粗略的概念，使用现有的几何图形 (THREE.PlaneGeometry())，它为图表下方的区域着色。但请记住，当您需要在一张图表中仅显示正值或仅负值时，可以使用这种方法，否则，结果会看起来很奇怪（或者说丑陋）。

var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 1, 1000);
camera.position.set(0, 2, 10);
var renderer = new THREE.WebGLRenderer({
  antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

var controls = new THREE.OrbitControls(camera, renderer.domElement);

var points = [],
  pointCount = 21;
var plane, line;

scene.add(new THREE.GridHelper( pointCount - 1, pointCount -1 ));

for (let i = 0; i < pointCount; i++) {
  points.push({
    initValue: THREE.Math.randFloat(-1, 1),
    amplitude: THREE.Math.randFloat(1, 2),
    speed: THREE.Math.randFloat(.5, 2)
  });
}

createGraph( pointCount );

function createGraph( pointCount ) {
  var planeGeom = new THREE.PlaneGeometry(pointCount - 1, 1, pointCount - 1, 1);
  planeGeom.translate(0, .5, 0);

  plane = new THREE.Mesh(planeGeom, new THREE.MeshBasicMaterial({
    color: "red",
    wireframe: false,
    side: THREE.DoubleSide,
    transparent: true,
    opacity: .75
  }));
  scene.add(plane);

  var lineGeom = new THREE.Geometry();
  for (let i = 0; i < plane.geometry.parameters.widthSegments + 1; i++) {
    lineGeom.vertices.push(planeGeom.vertices[i]); // share the upper points of the plane
  }
  line = new THREE.Line(lineGeom, new THREE.LineBasicMaterial({
    color: "aqua"
  }));
  plane.add(line);
}


var time = 0;

render();

function render() {
  time = Date.now() * .001;
  requestAnimationFrame(render);
  points.forEach( ( p, idx ) => {
    plane.geometry.vertices[idx].y = 2.5 + Math.sin( (time + p.initValue) * p.speed) * p.amplitude;  // the trick is that indices of upper vertices are from 0 to N consequently in row (r87),
    // thus we can assign the data from the `points` array to their Y-coordinates to form the graph
  });
  plane.geometry.verticesNeedUpdate = true; // the most important thing when you change coordiantes of vertices
  line.geometry.verticesNeedUpdate = true; // the most important thing when you change coordiantes of vertices
  renderer.render(scene, camera);
}

body {
  overflow: hidden;
  margin: 0;
}

<script src="https://threejs.org/build/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>

【讨论】：

【解决方案3】：

考虑到要填充的整个图形，您需要创建 1 个大形状。因此，就像在您的图像中一样，然后包含轴。

然后你可以用任何类型的材料填充形状。

以下是threejs网站上的一些示例：

https://threejs.org/examples/?q=shape#webgl_geometry_extrude_shapes2 https://threejs.org/examples/?q=shape#webgl_geometry_shapes

您可能不需要像这些示例中那样进行挤压。

【讨论】：