画一个坐标系

作者: waka | 来源:发表于2017-09-28 11:09 被阅读57次

画一个坐标系
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参考文章： Threejs基础教程第2章还记得点、线、面吗(二)
THREE笛卡尔右手坐标系详解

学习 Three.js 的时候跟着老师做，但是发现视角有些难以理解，于是自己画了一个，个人认为比较容易理解

黄色为Y轴，紫色为X轴，红色为Z轴

github地址：https://github.com/BadWaka/BadWaka.github.io/blob/master/views/three/three-demo-2-2.html

代码如下：（依赖 three.js）

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>2-2</title>
    <style>
        html, body, canvas {
            margin: 0;
            padding: 0;
            width: 100%;
            height: 100%;
        }

        div#canvas-frame {
            border: none;
            cursor: pointer;
            width: 100%;
            height: 600px;
            background-color: #EEEEEE;
        }
    </style>
</head>
<body onload="threeStart()">
<div id="canvas-frame"></div>
<script src="../../library/three/three.js"></script>
<script>

    // 渲染器
    var renderer;

    function initThree() {
        width = document.getElementById('canvas-frame').clientWidth;
        height = document.getElementById('canvas-frame').clientHeight;
        renderer = new THREE.WebGLRenderer({
            antialias: true
        });
        renderer.setSize(width, height);
        document.getElementById('canvas-frame').appendChild(renderer.domElement);
        renderer.setClearColor(0xFFFFFF, 1.0);
    }

    // 相机
    var camera;

    function initCamera() {
        camera = new THREE.PerspectiveCamera(45, width / height, 1, 10000);
        camera.position.x = 1000;
        camera.position.y = 1000;
        camera.position.z = 1000;
        camera.up.x = 0;
        camera.up.y = 1;
        camera.up.z = 0;
        camera.lookAt({
            x: 0,
            y: 0,
            z: 0
        });
    }

    // 场景
    var scene;

    function initScene() {
        scene = new THREE.Scene();
    }

    // 灯光
    var light;

    function initLight() {
        light = new THREE.DirectionalLight(0xFF0000, 1.0, 0);
        light.position.set(100, 100, 200);
        scene.add(light);
    }

    var cube;

    function initObject() {
        var geometry = new THREE.Geometry();
        geometry.vertices.push(new THREE.Vector3(-500, 0, 0));
        geometry.vertices.push(new THREE.Vector3(500, 0, 0));

        for (var i = 0; i <= 20; i++) {
            var line = new THREE.Line(geometry, new THREE.LineBasicMaterial({
                color: 0x000000,
                opacity: 0.2
            }));
            line.position.z = (i * 50) - 500;
            scene.add(line);

            var line = new THREE.Line(geometry, new THREE.LineBasicMaterial({
                color: 0x000000,
                opacity: 0.2
            }));
            line.position.x = (i * 50) - 500;
            line.rotation.y = 90 * Math.PI / 180;
            scene.add(line);
        }

        // Y坐标
        var lineY = new THREE.Line(geometry, new THREE.LineBasicMaterial({
            color: 0xFFD700,    // 黄色
            opacity: 0.2
        }));
        lineY.position.y = 500;
        lineY.rotation.z = 90 * Math.PI / 180;
        scene.add(lineY);

        // X坐标
        var lineX = new THREE.Line(geometry, new THREE.LineBasicMaterial({
            color: 0xFF00FF,    // 紫色
            opacity: 0.2
        }));
        lineX.position.x = 500;
        scene.add(lineX);

        // Z坐标
        var lineZ = new THREE.Line(geometry, new THREE.LineBasicMaterial({
            color: 0xEE3B3B,    // 红色
            opacity: 0.2
        }));
        lineZ.position.z = 500;
        lineZ.rotation.y = 90 * Math.PI / 180;
        scene.add(lineZ);

    }

    // 开始画3D
    function threeStart() {
        initThree();
        initCamera();
        initScene();
        initLight();
        initObject();
        renderer.clear();
        renderer.render(scene, camera);
    }

</script>
</body>
</html>