Version: 2017.2 (switch to 2017.3b)
Built-in shader helper functions
Making multiple shader program variants
Other Versions

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.cginc include file that is included automatically.

Transformations

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.

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.

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.

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.

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.

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.

Did you find this page useful? Please give it a rating:

Built-in shader helper functions
Making multiple shader program variants