babylon.js 学习笔记(8)

接上回继续，现在的村庄已经有点象样了，但是远处的背景仍比较单调(如下图），今天来学习如何处理天空背景。

babylon.js中，把整个空间假象成一个巨大的立方体(称为SkyBox)，然后依次给立方体的6个面，贴上天空的背景图(如下图)

在代码中只要指定这6张图的rootUrl即可，babylon.js会自动拼上一系列后缀，按如下约定去加载图片：

_px.jpg	_nx.jpg	_py.jpg	_ny.jpg	_pz.jpg	_nz.jpg

这个不用死记：p指positive(坐标轴正向)，n指negtive(坐标轴负向)，所以_px.jpg，即贴在x轴正向（即：立方体右面），类似的 _nz.jpg，就是z轴负方向（立方体前面）

参考代码如下：重点在于CubeTexture的使用

var createScene = function () {
    var scene = new BABYLON.Scene(engine);
    var camera = new BABYLON.ArcRotateCamera("Camera", -Math.PI / 2, Math.PI / 2, 40, new BABYLON.Vector3(0, 0, 0), scene);
    camera.attachControl(canvas, true);

    var light = new BABYLON.HemisphericLight("hemiLight", new BABYLON.Vector3(-1, 1, 0), scene);
    light.diffuse = new BABYLON.Color3(1, 0, 0);

    // Skybox
    var skybox = BABYLON.MeshBuilder.CreateBox("skyBoxDemo", { size: 15.0 }, scene);
    var skyboxMaterial = new BABYLON.StandardMaterial("skyBox1", scene);
    skyboxMaterial.backFaceCulling = false;
    skyboxMaterial.reflectionTexture = new BABYLON.CubeTexture("../assets/img/sky/skybox", scene);
    skyboxMaterial.reflectionTexture.coordinatesMode = BABYLON.Texture.SKYBOX_MODE;
    skyboxMaterial.diffuseColor = new BABYLON.Color3(0, 0, 0);
    skyboxMaterial.specularColor = new BABYLON.Color3(0, 0, 0);
    skybox.material = skyboxMaterial;

    return scene;

};

注意目录的相对路径：

在线地址： https://yjmyzz.github.io/babylon_js_study/day08/01.html

当这个SkyBox放到足够大时，就会产生天空背景的效果：

var createScene = function () {
    ...
    //设置摄像机的radius为5(离目标近一点)
    var camera = new BABYLON.ArcRotateCamera("Camera", -Math.PI / 2, Math.PI / 2, 5, BABYLON.Vector3.Zero(), scene);
   ...
    //Skybox（设置size调整成1000）
    var skybox = BABYLON.MeshBuilder.CreateBox("skyBoxDemo", { size: 1000.0 }, scene);
    ...
    return scene;

};

在线地址 ：https://yjmyzz.github.io/babylon_js_study/day08/02.html

将这个天空背景应用到先前画的村庄：

const createScene = () => {
    const scene = new BABYLON.Scene(engine);

    const camera = new BABYLON.ArcRotateCamera("camera", -Math.PI / 3.5, Math.PI / 1.5, 30, new BABYLON.Vector3(0, 0, 0));

    camera.attachControl(canvas, true);
    const light = new BABYLON.HemisphericLight("light", new BABYLON.Vector3(1, 1, 0));

    //导入村庄的模型
    BABYLON.SceneLoader.ImportMeshAsync("", "../assets/glb/", "valleyvillage.glb");

    // Skybox
    var skybox = BABYLON.MeshBuilder.CreateBox("skybox", { size: 1000.0 }, scene);
    var skyboxMaterial = new BABYLON.StandardMaterial("skybox", scene);
    skyboxMaterial.backFaceCulling = false;
    skyboxMaterial.reflectionTexture = new BABYLON.CubeTexture("../assets/img/sky/skybox", scene);
    skyboxMaterial.reflectionTexture.coordinatesMode = BABYLON.Texture.SKYBOX_MODE;
    skyboxMaterial.diffuseColor = new BABYLON.Color3(0, 0, 0);
    skyboxMaterial.specularColor = new BABYLON.Color3(0, 0, 0);
    skybox.material = skyboxMaterial;

    //限制攝像的視角
    camera.upperBetaLimit = Math.PI / 2.2;

    return scene;
}

在线地址: https://yjmyzz.github.io/babylon_js_study/day08/03.html

调整reflectionTexture.coordinatesMode的枚举值，还能产生类似"天空之镜"的效果：

const createScene = () => {
    const scene = new BABYLON.Scene(engine);

    const camera = new BABYLON.ArcRotateCamera("camera", -Math.PI / 3.5, Math.PI / 1.5, 30, new BABYLON.Vector3(0, 0, 0));
    camera.upperBetaLimit = Math.PI / 1.5;
    camera.attachControl(canvas, true);
    const light = new BABYLON.HemisphericLight("light", new BABYLON.Vector3(1, 1, 0));

    // Skybox
    var skybox = BABYLON.MeshBuilder.CreateBox("skybox", { size: 1000.0 }, scene);
    var skyboxMaterial = new BABYLON.StandardMaterial("skybox", scene);
    skyboxMaterial.backFaceCulling = false;
    skyboxMaterial.reflectionTexture = new BABYLON.CubeTexture("../assets/img/sky/skybox", scene);
    skyboxMaterial.reflectionTexture.coordinatesMode = BABYLON.Texture.SKYBOX_MODE;
    skyboxMaterial.diffuseColor = new BABYLON.Color3(0, 0, 0);
    skyboxMaterial.specularColor = new BABYLON.Color3(0, 0, 0);
    skybox.material = skyboxMaterial;

    var shapeMaterial = new BABYLON.StandardMaterial("mat", scene);
    shapeMaterial.backFaceCulling = true;
    shapeMaterial.reflectionTexture = new BABYLON.CubeTexture("../assets/img/sky/skybox", scene);
    //指定为“平面模式”
    shapeMaterial.reflectionTexture.coordinatesMode = BABYLON.Texture.PLANAR_MODE;
    shapeMaterial.diffuseColor = new BABYLON.Color3(0.1, 0.1, 0.1);
    shapeMaterial.specularColor = new BABYLON.Color3(0.1, 0.1, 0.1);

    // Box
    var box = BABYLON.MeshBuilder.CreateBox("box", { size: 5 }, scene);
    box.material = shapeMaterial;
    box.position.x = -20;
    box.rotation.y = Math.PI / 8;
    box.rotation.x = -Math.PI / 4;

    // Sphere
    var ball = BABYLON.MeshBuilder.CreateSphere("ball", { diameter: 8 }, scene);
    ball.material = shapeMaterial;
    ball.position = new BABYLON.Vector3(-5, 2, 5);
    ball.rotation.y = Math.PI / 8;
    ball.rotation.x = -Math.PI / 8;

    //Ground
    var ground = BABYLON.MeshBuilder.CreateGround("ground", { width: 6, height: 6 }, scene);
    ground.material = shapeMaterial;
    ground.position = new BABYLON.Vector3(10, 0, 5);
    ground.rotation.y = Math.PI / 8;
    ground.rotation.x = -Math.PI / 2;
    return scene;
}

在线地址：https://yjmyzz.github.io/babylon_js_study/day08/04.html

参考文档：

https://doc.babylonjs.com/features/introductionToFeatures/chap5/sky

https://doc.babylonjs.com/features/featuresDeepDive/materials/using/reflectionTexture