Unity

• Built-in shader variables

Built-in shader helper functions

Making multiple shader program variants

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Built-in shader variables

Unity provides a handful of built-in global variables for your shadersA small script that contains the mathematical calculations and algorithms for calculating the Color of each pixel rendered, based on the lighting input and the Material configuration. More info
See in Glossary: 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.
unity_ObjectToWorld	Current model matrix.
unity_WorldToObject	Inverse of current world matrix.

Camera and screen

These variables will correspond to the CameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary that is renderingThe process of drawing graphics to the screen (or to a render texture). By default, the main camera in Unity renders its view to the screen. More info
See in Glossary. 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 width of the camera’s target texture in pixelsThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info See in Glossary, y is the height of the camera’s target texture 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 PathThe technique Unity uses to render graphics. Choosing a different path affects the performance of your game, and how lighting and shading are calculated. Some paths are more suited to different platforms and hardware than others. More info
See in Glossary is used, and which LightMode Pass Tag is used in the shader.

Forward renderingA rendering path that renders each object in one or more passes, depending on lights that affect the object. Lights themselves are also treated differently by Forward Rendering, depending on their settings and intensity. More info
See in Glossary (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.
unity_WorldToShadow	float4x4[4]	World-to-shadow matrices. One matrix for spot lights, up to four for directional light cascades.

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.
unity_WorldToShadow	float4x4[4]	World-to-shadow matrices. One matrix for spot lights, up to four for directional light cascades.

Spherical harmonics coefficients (used by ambient and light probes) are set up for ForwardBase, PrePassFinal and Deferredpass 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.
_TextureSampleAdd	float4	Set automatically by Unity for UI(User Interface) Allows a user to interact with your application. More info See in Glossary only based on whether the texture being used is in Alpha8 format (the value is set to (1,1,1,0)) or not (the value is set to (0,0,0,0)).

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