Built-in shader variables
Unity provides a handful of built-in global variables for your shaders: things like current object’s transformation matrices, light parameters, current time and so on. You use them in shader programs like any other variable, the only difference is that you don’t have to declare them - they are all declared in
UnityShaderVariables.cgincinclude file that is included automatically.
Unity提供了非常有用的内置全局变量，比如：当前Object的变换矩阵、光照参数、当前时间等。内置变量与其他变量一样能在Shader程序中使用，唯一不同的是，不需要再重新定义它们，这些变量都定义在
UnityShaderVariables.cginc(unity安装目录下查找)中
Transformations
All these matrices are float4x4 type.
| Name | Value |
| UNITY_MATRIX_MVP | Current model * view * projection matrix. 当前模型视图投影矩阵 |
| UNITY_MATRIX_MV | Current model * view matrix. 当前模型视图矩阵 |
| UNITY_MATRIX_V | Current view matrix.当前视图矩阵 |
| UNITY_MATRIX_P | Current projection matrix.当前投影矩阵 |
| UNITY_MATRIX_VP | Current view * projection matrix.当前视图投影矩阵 |
| UNITY_MATRIX_T_MV | Transpose of model * view matrix.模型视图矩阵的转置 |
| UNITY_MATRIX_IT_MV | Inverse transpose of model * view matrix.模型视图矩阵的逆 |
| _Object2World | Current model matrix.模型世界坐标矩阵（本地坐标转世界坐标） |
| _World2Object | Inverse of current world matrix.模型世界坐标矩阵的逆（世界坐标转本地坐标） |
Camera and screen
These variables will correspond to the Camera that is rendering. For example during shadowmap rendering, they will still refer to the Camera component values, and not the “virtual camera” that is used for the shadowmap projection.
这些变量是对渲染相机而言的。比如阴影渲染将会涉及到相机组件的变量，虚拟相机无法用于阴影投影
| Name | Type | Value |
| _WorldSpaceCameraPos | float3 | World space position of the camera.相机世界坐标 |
| _ProjectionParams | float4 | x is 1.0 (or –1.0 if currently rendering with a flipped projection matrix), y is the camera’s near plane, z is the camera’s far plane and w is 1/FarPlane.x是1.0（或-1.0，如果目前以翻转投影矩阵 渲染），y是相机的近平面，z是相机的远平面和w是1 / FarPlane.x。 |
| _ScreenParams | float4 | x is the camera’s render target width in pixels, y is the camera’s render target height in pixels, z is 1.0 + 1.0/width and w is 1.0 + 1.0/height. |
| _ZBufferParams | float4 |
Used to linearize Z buffer values.
x is (1-far/near), y is (far/near), z is (x/far) and w is (y/far).
用于线性Z缓冲器值。
x
是（1-far/near），
y
是（far/near），
z
为（x /
far
）和
w
是（y /
far
）。
|
| unity_OrthoParams | float4 |
x is orthographic camera’s width, y is orthographic camera’s height, z is unused and w is 1.0 when camera is orthographic, 0.0 when perspective.
x
在正交相机的宽，
y
在正交相机标的高度，z没有使用,当时正交相机的时候w是1，是透视相机的时候为0
|
| unity_CameraProjection | float4x4 | Camera’s projection matrix.相机投影矩阵 |
| unity_CameraInvProjection | float4x4 | Inverse of camera’s projection matrix.相机投影矩阵的逆 |
| unity_CameraWorldClipPlanes[6] | float4 |
Camera frustum plane world space equations, in this order: left, right, bottom, top, near, far.、
机视锥平面的世界空间方程，顺序如下：左，右，底，顶，近，远。
|
Time
| Name | Type | Value |
| _Time | float4 | Time since level load (t/20, t, t*2, t*3), use to animate things inside the shaders. |
| _SinTime | float4 | Sine of time: (t/8, t/4, t/2, t). |
| _CosTime | float4 | Cosine of time: (t/8, t/4, t/2, t). |
| unity_DeltaTime | float4 | Delta time: (dt, 1/dt, smoothDt, 1/smoothDt). |
Lighting
Light parameters are passed to shaders in different ways depending on which Rendering Path is used, and which LightMode Pass Tag is used in the shader.
光照参数：根据使用的渲染路径传入的参数，及在Shader中使用的光照模式
| Name | Type | Value |
| _LightColor0 (declared in Lighting.cginc) | fixed4 | Light color. |
| _WorldSpaceLightPos0 | float4 | Directional lights: (world space direction, 0). Other lights: (world space position, 1). |
| _LightMatrix0 (declared in AutoLight.cginc) | float4x4 | World-to-light matrix. Used to sample cookie & attenuation textures. |
| unity_4LightPosX0, unity_4LightPosY0, unity_4LightPosZ0 | float4 | (ForwardBase pass only) world space positions of first four non-important point lights. |
| unity_4LightAtten0 | float4 | (ForwardBase pass only) attenuation factors of first four non-important point lights. |
| unity_LightColor | half4[4] | (ForwardBase pass only) colors of of first four non-important point lights. |
Deferred shading and deferred lighting, used in the lighting pass shader (all declared in UnityDeferredLibrary.cginc):
| Name | Type | Value |
| _LightColor | float4 | Light color. |
| _LightMatrix0 | float4x4 | World-to-light matrix. Used to sample cookie & attenuation textures. |
Spherical harmonics coefficients (used by ambient and light probes) are set up for ForwardBase, PrePassFinal and Deferred pass types. They contain 3rd order SH to be evaluated by world space normal (see ShadeSH9 from UnityCG.cginc). The variables are all half4 type, unity_SHAr and similar names.
Vertex-lit rendering (Vertex pass type):
Up to 8 lights are set up for a Vertex pass type; always sorted starting from the brightest one. So if you want to render objects affected by two lights at once, you can just take first two entries in the arrays. If there are less lights affecting the object than 8, the rest will have their color set to black.
| Name | Type | Value |
| unity_LightColor | half4[8] | Light colors. |
| unity_LightPosition | float4[8] | View-space light positions. (-direction,0) for directional lights; (position,1) for point/spot lights. |
| unity_LightAtten | half4[8] | Light attenuation factors. x is cos(spotAngle/2) or –1 for non-spot lights; y is 1/cos(spotAngle/4) or 1 for non-spot lights; z is quadratic attenuation; w is squared light range. |
| unity_SpotDirection | float4[8] | View-space spot light positions; (0,0,1,0) for non-spot lights. |
Fog and Ambient
| Name | Type | Value |
| unity_AmbientSky | fixed4 | Sky ambient lighting color in gradient ambient lighting case. |
| unity_AmbientEquator | fixed4 | Equator ambient lighting color in gradient ambient lighting case. |
| unity_AmbientGround | fixed4 | Ground ambient lighting color in gradient ambient lighting case. |
| UNITY_LIGHTMODEL_AMBIENT | fixed4 | Ambient lighting color (sky color in gradient ambient case). Legacy variable. |
| unity_FogColor | fixed4 | Fog color. |
| unity_FogParams | float4 | Parameters for fog calculation: (density / sqrt(ln(2)), density / ln(2), –1/(end-start), end/(end-start)). x is useful for Exp2 fog mode, y for Exp mode, z and w for Linear mode. |
Various
| Name | Type | Value |
| unity_LODFade | float4 | Level-of-detail fade when using LODGroup. x is fade (0..1), y is fade quantized to 16 levels, z and w unused. |