Three.js基础探寻九——网格

时间：2021-08-10 05:55:44

　　在学习了几何形状和材质之后，我们就能使用他们来创建物体了。最常用的一种物体就是网格（Mesh），网格是由顶点、边、面等组成的物体；其他物体包括线段（Line）、骨骼（Bone）、粒子系统（ParticleSystem）等。创建物体需要指定几何形状和材质，其中，几何形状决定了物体的顶点位置等信息，材质决定了物体的颜色、纹理等信息。

　　本篇将介绍创建较为常用的物体：网格，然后介绍如何修改物体的属性。

1.创建网格

　　在前几篇中，我们学习了如何创建几何形状与材质，而网格的创建非常简单，只要把几何形状与材质传入其构造函数。最常用的物体是网格（Mesh），它代表包含点、线、面的几何体，其构造函数是： 

Mesh(geometry, material)

　　下面，让我们通过一个具体的例子了解如何创建网格：

var material = new THREE.MeshLambertMaterial({

    color: 0xffff00

});

var geometry = new THREE.CubeGeometry(1, 2, 3);

var mesh = new THREE.Mesh(geometry, material);

scene.add(mesh);

　　如果material和geometry之后不会复用的话，也可以合在一起写为： 

var mesh = new THREE.Mesh(new THREE.CubeGeometry(1, 2, 3),

new THREE.MeshLambertMaterial({

        color: 0xffff00

    })

);

scene.add(mesh);

　　添加光照后，得到的效果为：

Three.js基础探寻九——网格

　　如果不指定material，则每次会随机分配一种wireframe为true的材质，每次刷新页面后的颜色是不同的，一种可能的效果是：

Three.js基础探寻九——网格

　　源码：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>3.js测试9.1</title> 
</head>
<body onload="init()">
<canvas id="mainCanvas" width="400px" height="300px" ></canvas>
</body>
<script type="text/javascript" src="js/three.min.js"></script>
<script type="text/javascript">
function init() {
var renderer = new THREE.WebGLRenderer({
                canvas: document.getElementById('mainCanvas')
            });
            renderer.setClearColor(0x000000);
var scene = new THREE.Scene();

// camera
var camera = new THREE.OrthographicCamera(-2.5, 2.5, 1.875, -1.875, 0.1, 100);
            camera.position.set(5, 5, 20);
            camera.lookAt(new THREE.Vector3(0, 0, 0));
            scene.add(camera);

var material = new THREE.MeshLambertMaterial({
                color: 0xffff00
            });
//          var material = new THREE.MeshBasicMaterial({
//              color: 0xffff00,
//              wireframe: true
//          });
var geometry = new THREE.CubeGeometry(1, 2, 3);
var mesh = new THREE.Mesh(geometry, material);
            scene.add(mesh);

var light = new THREE.DirectionalLight(0xffffff);
            light.position.set(20, 10, 5);
            scene.add(light);

// render
            renderer.render(scene, camera);
        }
</script>
</html>

 

 

 

2.修改属性

　　2.1 修改材质

　　除了在构造函数中指定材质，在网格被创建后，也能对材质进行修改：

var material = new THREE.MeshLambertMaterial({

    color: 0xffff00

});

var geometry = new THREE.CubeGeometry(1, 2, 3);

var mesh = new THREE.Mesh(geometry, material);

    scene.add(mesh);

mesh.material = new THREE.MeshLambertMaterial({

    color: 0xff0000

});

　　最终显示的颜色是红色：

Three.js基础探寻九——网格

　　源码：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>3.js测试9.2</title> 
</head>
<body onload="init()">
<canvas id="mainCanvas" width="400px" height="300px" ></canvas>
</body>
<script type="text/javascript" src="js/three.min.js"></script>  
<script type="text/javascript">
function init() {
var renderer = new THREE.WebGLRenderer({
                canvas: document.getElementById('mainCanvas')
            });
            renderer.setClearColor(0x000000);
var scene = new THREE.Scene();

// camera
var camera = new THREE.OrthographicCamera(-2.5, 2.5, 1.875, -1.875, 0.1, 100);
            camera.position.set(5, 5, 20);
            camera.lookAt(new THREE.Vector3(0, 0, 0));
            scene.add(camera);

var material = new THREE.MeshLambertMaterial({
                color: 0xffff00
            });
var geometry = new THREE.CubeGeometry(1, 2, 3);
var mesh = new THREE.Mesh(geometry, material);
            scene.add(mesh);

            mesh.material = new THREE.MeshLambertMaterial({
                color: 0xff0000
            });

var light = new THREE.DirectionalLight(0xffffff);
            light.position.set(20, 10, 5);
            scene.add(light);

// render
            renderer.render(scene, camera);
        }
</script>
</html>

　　2.2 位置、缩放、旋转

　　位置、缩放、旋转是物体三个常用属性。由于THREE.Mesh基础自THREE.Object3D，因此包含scale、rotation、position三个属性。它们都是THREE.Vector3实例，因此修改其值的方法是相同的，这里以位置为例。

　　THREE.Vector3有x、y、z三个属性，如果只设置其中一个属性，则可以用以下方法： 

mesh.position.z = 1;

　　如果需要同时设置多个属性，可以使用以下两种方法：

mesh.position.set(1.5, -0.5, 0);

　　或者：

mesh.position = new THREE.Vector3(1.5, -0.5, 0);

　　缩放对应的属性是scale，旋转对应的属性是rotation，具体方法与上例相同，分别表示沿x、y、z三轴缩放或旋转。

Three.js基础探寻九——网格

　　源码：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>3.js测试9.3</title>
</head>
<body onload="init()">
<canvas id="mainCanvas" width="400px" height="300px" ></canvas>
</body>
<script type="text/javascript" src="js/three.min.js"></script>
<script type="text/javascript">
function init() {
var renderer = new THREE.WebGLRenderer({
                canvas: document.getElementById('mainCanvas')
            });
            renderer.setClearColor(0x000000);
var scene = new THREE.Scene();

// camera
var camera = new THREE.OrthographicCamera(-2.5, 2.5, 1.875, -1.875, 0.1, 100);
            camera.position.set(5, 5, 20);
            camera.lookAt(new THREE.Vector3(0, 0, 0));
            scene.add(camera);

var material = new THREE.MeshLambertMaterial({
                color: 0xffff00
            });
var geometry = new THREE.CubeGeometry(1, 2, 3);
var mesh = new THREE.Mesh(geometry, material);
            scene.add(mesh);

            mesh.position.set(1.5, -0.5, 0);
            mesh.position = new THREE.Vector3(1.5, -0.5, 0);
            mesh.position.z = 1;

var light = new THREE.DirectionalLight(0xffffff);
            light.position.set(20, 10, 5);
            scene.add(light);

            drawAxes(scene);

// render
            renderer.render(scene, camera);
        }

function drawAxes(scene) {
// x-axis
var xGeo = new THREE.Geometry();
            xGeo.vertices.push(new THREE.Vector3(0, 0, 0));
            xGeo.vertices.push(new THREE.Vector3(1, 0, 0));
var xMat = new THREE.LineBasicMaterial({
                color: 0xff0000
            });
var xAxis = new THREE.Line(xGeo, xMat);
            scene.add(xAxis);

// y-axis
var yGeo = new THREE.Geometry();
            yGeo.vertices.push(new THREE.Vector3(0, 0, 0));
            yGeo.vertices.push(new THREE.Vector3(0, 1, 0));
var yMat = new THREE.LineBasicMaterial({
                color: 0x00ff00
            });
var yAxis = new THREE.Line(yGeo, yMat);
            scene.add(yAxis);

// z-axis
var zGeo = new THREE.Geometry();
            zGeo.vertices.push(new THREE.Vector3(0, 0, 0));
            zGeo.vertices.push(new THREE.Vector3(0, 0, 1));
var zMat = new THREE.LineBasicMaterial({
                color: 0x00ccff
            });
var zAxis = new THREE.Line(zGeo, zMat);
            scene.add(zAxis);
        }
</script>
</html>

 

 

整理自张雯莉《Three.js入门指南》

 

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