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.cginc
include file that is included automatically.
All these matrices are float4x4
type.
Name | Value |
UNITY_MATRIX_MVP | Current model * view * projection matrix. |
UNITY_MATRIX_MV | Current model * view matrix. |
UNITY_MATRIX_V | Current view matrix. |
UNITY_MATRIX_P | Current projection matrix. |
UNITY_MATRIX_VP | Current view * projection matrix. |
UNITY_MATRIX_T_MV | Transpose of model * view matrix. |
UNITY_MATRIX_IT_MV | Inverse transpose of model * view matrix. |
_Object2World | Current model matrix. |
_World2Object | Inverse of current world matrix. |
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.
Name | Type | Value |
_WorldSpaceCameraPos | float3 | World space position of the camera. |
_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. |
_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). |
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. |
unity_CameraProjection | float4x4 | Camera’s projection matrix. |
unity_CameraInvProjection | float4x4 | Inverse of camera’s projection matrix. |
unity_CameraWorldClipPlanes[6] | float4 | Camera frustum plane world space equations, in this order: left, right, bottom, top, near, far. |
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). |
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.
Forward rendering (ForwardBase
and ForwardAdd
pass types):
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. |
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. |
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. |