Enviroment

官网地址：https://material.io/guidelines/material-design/environment.html
Material design is a three-dimensional environment containing light, material, and cast shadows.
Material design是一个包含了光，材质，以及投影的三维环境。
All material objects have x, y, and z dimensions.
所有的material对象都有x,y,和z值。
All material objects have a single z-axis position.
所有的material对象都有一个唯一的z轴位置。
Key lights create directional shadows, and ambient light creates soft shadows.
主光线生成了定向阴影，背景光则生成了软阴影。
Material thickness
Material的密度
1dp
Shadows
阴影
Shadows are created by the elevation difference between overlapping material.
两个不同材料之间的高度生成了阴影。

what_is_material_environment.png

Contents
目录
3D world
Light and shadow

• 3D world
  The material environment is a 3D space, which means all objects have x, y, and z dimensions. The z-axis is perpendicularly aligned to the plane of the display, with the positive z-axis extending towards the viewer. Every sheet of material occupies a single position along the z-axis and has a standard 1dp thickness, equivalent toone pixel of thicknesson screens with a pixel density of 160.
  material环境是一个3D空间，这意味着所有的对象都有x,y和z值。z轴垂直于显示的屏幕，正z轴的方向朝向用户。每片材料沿z轴占据一个1dp厚度标准的单独位置，相当于像素密度为160的厚度屏幕的像素。
  On the web, the z-axis is used for layering and not for perspective. The 3D world is emulated by manipulating the y-axis.
  在网页上，z轴用于分层，而不用于透视。通过操纵y轴来模拟3D世界。
  3D space with x, y, and z axes
  3D空间拥有x,y和z

whatismaterial_environment_3d.png

• Light and shadow
  Within the material environment, virtual lights illuminate the scene. Key lights create directional shadows, while ambient light creates soft shadows from all angles.
  在material环境中，虚拟光线照亮了屏幕。主光线生成了方向阴影，而周围的光则从各个角度生成了软阴影。
  Shadows in the material environment are cast by these two light sources. In Android development, shadows occur when light sources are blocked by sheets of material at various positions along the z-axis. On the web, shadows are depicted by manipulating the y-axis only. The following example shows the card with a height of 6dp.
  material环境中的阴影有这两种光源产生。在Android的发展中，当沿着z轴的各个位置的光源受到材料片的阻挡时，就会产生阴影。在网络上，仅通过操纵y轴来描绘阴影。下面的例子展示了6 dp高度时的卡片。

whatismaterial_environment_shadow1.png

Shadow cast by key light
主光源生成的阴影

whatismaterial_environment_shadow2.png

Shadow cast by ambient light
周围光源生成的阴影

whatismaterial_environment_shadow3.png

Combined shadow from key and ambient lights
联合主光源和周围光线生成的阴影