Vertex and fragment programs

【Vertex and fragment programs】

　　When you use vertex and fragment programs (the so called "programmable pipeline"), most of the hardcoded functionality ("fixed function pipeline") in the graphics hardware is switched off. For example, using a vertex program turns off standard 3D transformations, lighting and texture coordinate generation completely. Similarly, using a fragment program replaces any texture combine modes that would be defined in SetTexture commands; thus SetTexture commands are not needed.

【Using Cg in ShaderLab】

　　Shaders in ShaderLab are usually written in Cg programming language by embedding "Cg snippets" in the shader text. Cg snippets are compiled into low-level shader assembly by the Unity editor, and the final shader that is included in your game's data files only contains this low-level assembly.

　　Note that because Cg code is compiled by the editor, you can't create Cg shaders from scripts at runtime.（OpenGL的glCompileShader提供运行时创建Shader的能力）

　　In general, Cg snippets are placed inside Pass blocks. They look like this:

　　 Vertex and fragment programs

　　The following example demonstrates a complete shader with Cg programs that renders object normals as colors:　　

Shader "Tutorial/Display Normals" {
SubShader {
    Pass {

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"

struct v2f {
    float4 pos : SV_POSITION;
    float3 color : COLOR0;
};

v2f vert (appdata_base v)
{
    v2f o;
    o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
    o.color = v.normal * 0.5 + 0.5;
    return o;
}

half4 frag (v2f i) : COLOR
{
    return half4 (i.color, 1);
}
ENDCG

    }
}
Fallback "VertexLit"
}

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