All Shaders files in Unity are written in a declarative language called “ShaderLab”. In the file, a nested-braces
syntax declares various things that describe the shader – for example which shader properties should be shown in material inspector;
what kind of hardware fallbacks to do; what kind of blending modes to use etc.; and actual “shader code” is written in
CGPROGRAM snippets inside the same shader file (see surface shaders and vertex and fragment shaders).
This page and the child pages describes the nested-braces “ShaderLab” syntax. The CGPROGRAM snippets are written in regular
HLSL/Cg shading language, see their documentation pages.
Shader is the root command of a shader file. Each file must define one (and only one) Shader. It specifies how any objects whose material uses this shader are rendered.
Shader "name" { [Properties] Subshaders [Fallback] [CustomEditor] }
Defines a shader. It will appear in the material inspector listed under name. Shaders optionally can define a list of properties that show up in material inspector. After this comes a list of SubShaders, and optionally a fallback and/or a custom editor declaration.
Shaders can have a list of properties. Any properties declared in a shader are shown in the material inspector inside Unity. Typical properties are the object color, textures, or just arbitrary values to be used by the shader.
Each shader is comprised of a list of sub-shaders. You must have at least one. When loading a shader, Unity will go through the list of subshaders, and pick the first one that is supported by the end user’s machine. If no subshaders are supported, Unity will try to use fallback shader.
Different graphic cards have different capabilities. This raises an eternal issue for game developers; you want your game to look great on the latest hardware, but don’t want it to be available only to those 3% of the population. This is where subshaders come in. Create one subshader that has all the fancy graphic effects you can dream of, then add more subshaders for older cards. These subshaders may implement the effect you want in a slower way, or they may choose not to implement some details.
Shader “level of detail” (LOD) and “shader replacement” are two techniques that also build upon subshaders, see Shader LOD and Shader Replacemement for details.
Here is one of the simplest shaders possible:
// colored vertex lighting
Shader "Simple colored lighting"
{
// a single color property
Properties {
_Color ("Main Color", Color) = (1,.5,.5,1)
}
// define one subshader
SubShader
{
// a single pass in our subshader
Pass
{
// use fixed function per-vertex lighting
Material
{
Diffuse [_Color]
}
Lighting On
}
}
}
This shader defines a color property _Color (that shows up in material inspector as Main Color) with a default value of (1,0.5,0.5,1). Then a single subshader is defined. The subshader consists of one Pass that turns on fixed-function vertex lighting and sets up basic material for it.
See more complex examples at Surface Shader Examples or Vertex and Fragment Shader Examples.