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.

Transformations

All these matrices are float4x4 type.

  NameValueUNITY_MATRIX_MVPCurrent model * view * projection matrix.UNITY_MATRIX_MVCurrent model * view matrix.UNITY_MATRIX_VCurrent view matrix.UNITY_MATRIX_PCurrent projection matrix.UNITY_MATRIX_VPCurrent view * projection matrix.UNITY_MATRIX_T_MVTranspose of model * view matrix.UNITY_MATRIX_IT_MVInverse transpose of model * view matrix._Object2WorldCurrent model matrix._World2ObjectInverse 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.

   NameTypeValue_WorldSpaceCameraPosfloat3World space position of the camera._ProjectionParamsfloat4x 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._ScreenParamsfloat4x 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._ZBufferParamsfloat4Used to linearize Z buffer values. x is (1-far/near), y is (far/near), z is (x/far) and w is (y/far).unity_OrthoParamsfloat4x 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_CameraProjectionfloat4x4Camera’s projection matrix.unity_CameraInvProjectionfloat4x4Inverse of camera’s projection matrix.unity_CameraWorldClipPlanes[6]float4Camera frustum plane world space equations, in this order: left, right, bottom, top, near, far.

Time

   NameTypeValue_Timefloat4Time since level load (t/20, t, t*2, t*3), use to animate things inside the shaders._SinTimefloat4Sine of time: (t/8, t/4, t/2, t)._CosTimefloat4Cosine of time: (t/8, t/4, t/2, t).unity_DeltaTimefloat4Delta 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):

   NameTypeValue_LightColor0 (declared in Lighting.cginc)fixed4Light color._WorldSpaceLightPos0float4Directional lights: (world space direction, 0). Other lights: (world space position, 1)._LightMatrix0 (declared in AutoLight.cginc)float4x4World-to-light matrix. Used to sample cookie & attenuation textures.unity_4LightPosX0, unity_4LightPosY0, unity_4LightPosZ0float4(ForwardBase pass only) world space positions of first four non-important point lights.unity_4LightAtten0float4(ForwardBase pass only) attenuation factors of first four non-important point lights.unity_LightColorhalf4[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):

   NameTypeValue_LightColorfloat4Light color._LightMatrix0float4x4World-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.

   NameTypeValueunity_LightColorhalf4[8]Light colors.unity_LightPositionfloat4[8]View-space light positions. (-direction,0) for directional lights; (position,1) for point/spot lights.unity_LightAttenhalf4[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_SpotDirectionfloat4[8]View-space spot light positions; (0,0,1,0) for non-spot lights.

Fog and Ambient

   NameTypeValueunity_AmbientSkyfixed4Sky ambient lighting color in gradient ambient lighting case.unity_AmbientEquatorfixed4Equator ambient lighting color in gradient ambient lighting case.unity_AmbientGroundfixed4Ground ambient lighting color in gradient ambient lighting case.UNITY_LIGHTMODEL_AMBIENTfixed4Ambient lighting color (sky color in gradient ambient case). Legacy variable.unity_FogColorfixed4Fog color.unity_FogParamsfloat4Parameters 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

   NameTypeValueunity_LODFadefloat4Level-of-detail fade when using LODGroup. x is fade (0..1), y is fade quantized to 16 levels, z and w unused.