Providing vertex data to vertex programs

For Cg/HLSL vertex programs, the MeshThe main graphics primitive of Unity. Meshes make up a large part of your 3D worlds. Unity supports triangulated or Quadrangulated polygon meshes. Nurbs, Nurms, Subdiv surfaces must be converted to polygons. More info
See in Glossary vertex data is passed as inputs to the vertex shader function. Each input needs to have semantic speficied for it: for example, POSITION input is the vertex position, and NORMAL is the vertex normal.

Often, vertex data inputs are declared in a structure, instead of listing them one by one. Several commonly used vertex structures are defined in UnityCG.cginc include file, and in most cases it’s enough just to use those. The structures are:

• appdata_base: position, normal and one texture coordinate.
• appdata_tan: position, tangent, normal and one texture coordinate.
• appdata_full: position, tangent, normal, four texture coordinates and color.

Example: This shaderA program that runs on the GPU. More info
See in Glossary colors the mesh based on its normals, and uses appdata_base as vertex program input:

Shader "VertexInputSimple" {
    SubShader {
        Pass {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"
         
            struct v2f {
                float4 pos : SV_POSITION;
                fixed4 color : COLOR;
            };
            
            v2f vert (appdata_base v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.color.xyz = v.normal * 0.5 + 0.5;
                o.color.w = 1.0;
                return o;
            }

            fixed4 frag (v2f i) : SV_Target { return i.color; }
            ENDCG
        }
    } 
}

To access different vertex data, you need to declare the vertex structure yourself, or add input parameters to the vertex shader. Vertex data is identified by Cg/HLSL semantics, and must be from the following list:

• POSITION is the vertex position, typically a float3 or float4.
• NORMAL is the vertex normal, typically a float3.
• TEXCOORD0 is the first UV coordinate, typically float2, float3 or float4.
• TEXCOORD1, TEXCOORD2 and TEXCOORD3 are the 2nd, 3rd and 4th UV coordinates, respectively.
• TANGENT is the tangent vector (used for normal mapping), typically a float4.
• COLOR is the per-vertex color, typically a float4.

When the mesh data contains fewer components than are needed by the vertex shader input, the rest are filled with zeroes, except for the .w component which defaults to 1. For example, mesh texture coordinates are often 2D vectors with just x and y components. If a vertex shader declares a float4 input with TEXCOORD0 semantic, the value received by the vertex shaderA program that runs on each vertex of a 3D model when the model is being rendered. More info
See in Glossary will contain (x,y,0,1).

For examples of using these techniques to visualize vertex data in the Built-in Render Pipeline, see Visualizing vertex data.