Three.js基础探寻九——网格

时间 2020-07-16 标签 three.js js 基础探寻九网格

　　在学习了几何形状和材质以后，咱们就能使用他们来建立物体了。最经常使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；其余物体包括线段（Line）、骨骼（Bone）、粒子系统（ParticleSystem）等。建立物体须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。 javascript

　　本篇将介绍建立较为经常使用的物体：网格，而后介绍如何修改物体的属性。html

1.建立网格java

　　在前几篇中，咱们学习了如何建立几何形状与材质，而网格的建立很是简单，只要把几何形状与材质传入其构造函数。最经常使用的物体是网格（Mesh），它表明包含点、线、面的几何体，其构造函数是： canvas

Mesh(geometry, material)

　　下面，让咱们经过一个具体的例子了解如何建立网格：函数

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);

　　若是material和geometry以后不会复用的话，也能够合在一块儿写为：学习

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

    new THREE.MeshLambertMaterial({

        color: 0xffff00

    })

);

scene.add(mesh);

　　添加光照后，获得的效果为：测试

　　若是不指定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一样的，一种可能的效果是：spa

　　源码：3d

<!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code

　　2.1 修改材质

　　除了在构造函数中指定材质，在网格被建立后，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：

　　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、旋转是物体三个经常使用属性。因为THREE.Mesh基础自THREE.Object3D，所以包含scale、rotation、position三个属性。它们都是THREE.Vector3实例，所以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，若是只设置其中一个属性，则能够用如下方法：

mesh.position.z = 1;

　　若是须要同时设置多个属性，可使用如下两种方法：

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。

　　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》