Providing vertex data to vertex programs

For Cg/HLSL vertex programs, the vertex data must be passed in as a structure. Several commonly used vertex structures are defined in UnityCG.cginc include file, and in most cases it’s enough just to use them. The structures are:

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

For example, this shader colors the mesh based on it’s normals and just 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 = mul (UNITY_MATRIX_MVP, 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
    }
  } 
}

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

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

Examples

Visualizing UVs

The following shader example uses vertex position and first texture coordinate as vertex shader input (defined in structure appdata). It is very useful to debug UV coordinates of the mesh. UV coordinates are visualized as red and green colors, and coordinates outside of 0..1 range have additional blue tint applied.

Shader "Debug/UV 1" {
SubShader {
    Pass {
        Fog { Mode Off }
        CGPROGRAM

        #pragma vertex vert
        #pragma fragment frag

        // vertex input: position, UV
        struct appdata {
            float4 vertex : POSITION;
            float4 texcoord : TEXCOORD0;
        };

        struct v2f {
            float4 pos : SV_POSITION;
            float4 uv : TEXCOORD0;
        };
        
        v2f vert (appdata v) {
            v2f o;
            o.pos = mul( UNITY_MATRIX_MVP, v.vertex );
            o.uv = float4( v.texcoord.xy, 0, 0 );
            return o;
        }
        
        half4 frag( v2f i ) : SV_Target {
            half4 c = frac( i.uv );
            if (any(saturate(i.uv) - i.uv))
                c.b = 0.5;
            return c;
        }
        ENDCG
    }
}
}

Similarly, this shader vizualizes the second UV set of the model:

Shader "Debug/UV 2" {
SubShader {
    Pass {
        Fog { Mode Off }
        CGPROGRAM

        #pragma vertex vert
        #pragma fragment frag

        // vertex input: position, second UV
        struct appdata {
            float4 vertex : POSITION;
            float4 texcoord1 : TEXCOORD1;
        };

        struct v2f {
            float4 pos : SV_POSITION;
            float4 uv : TEXCOORD0;
        };
        
        v2f vert (appdata v) {
            v2f o;
            o.pos = mul( UNITY_MATRIX_MVP, v.vertex );
            o.uv = float4( v.texcoord1.xy, 0, 0 );
            return o;
        }
        
        half4 frag( v2f i ) : SV_Target {
            half4 c = frac( i.uv );
            if (any(saturate(i.uv) - i.uv))
                c.b = 0.5;
            return c;
        }
        ENDCG
    }
}
}

Visualizing vertex colors

The following shader uses vertex position and per-vertex colors as vertex shader input (defined in structure appdata).

Shader "Debug/Vertex color" {
SubShader {
    Pass {
        Fog { Mode Off }
        CGPROGRAM

        #pragma vertex vert
        #pragma fragment frag

        // vertex input: position, color
        struct appdata {
            float4 vertex : POSITION;
            fixed4 color : COLOR;
        };

        struct v2f {
            float4 pos : SV_POSITION;
            fixed4 color : COLOR;
        };
        
        v2f vert (appdata v) {
            v2f o;
            o.pos = mul( UNITY_MATRIX_MVP, v.vertex );
            o.color = v.color;
            return o;
        }
        
        fixed4 frag (v2f i) : SV_Target { return i.color; }
        ENDCG
    }
}
}

Visualizing normals

The following shader uses vertex position and normal as vertex shader input (defined in structure appdata). Normal’s X,Y,Z components are visualized as R,G,B colors. Because the normal components are in –1..1 range, we scale and bias them so that the output colors are in displayable 0..1 range.

Shader "Debug/Normals" {
SubShader {
    Pass {
        Fog { Mode Off }
        CGPROGRAM

        #pragma vertex vert
        #pragma fragment frag

        // vertex input: position, normal
        struct appdata {
            float4 vertex : POSITION;
            float3 normal : NORMAL;
        };

        struct v2f {
            float4 pos : SV_POSITION;
            fixed4 color : COLOR;
        };
        
        v2f vert (appdata v) {
            v2f o;
            o.pos = mul( UNITY_MATRIX_MVP, 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
    }
}
}

Visualizing tangents and binormals

Tangent and binormal vectors are used for normal mapping. In Unity only the tangent vector is stored in vertices, and binormal is derived from normal and tangent.

The following shader uses vertex position and tangent as vertex shader input (defined in structure appdata). Tangent’s X,Y,Z components are visualized as R,G,B colors. Because the normal components are in –1..1 range, we scale and bias them so that the output colors are in displayable 0..1 range.

Shader "Debug/Tangents" {
SubShader {
    Pass {
        Fog { Mode Off }
        CGPROGRAM

        #pragma vertex vert
        #pragma fragment frag

        // vertex input: position, tangent
        struct appdata {
            float4 vertex : POSITION;
            float4 tangent : TANGENT;
        };

        struct v2f {
            float4 pos : SV_POSITION;
            fixed4 color : COLOR;
        };
        
        v2f vert (appdata v) {
            v2f o;
            o.pos = mul( UNITY_MATRIX_MVP, v.vertex );
            o.color = v.tangent * 0.5 + 0.5;
            return o;
        }
        
        fixed4 frag (v2f i) : SV_Target { return i.color; }
        ENDCG
    }
}
}

The following shader visualizes binormals. It uses vertex position, normal and tangent as vertex input. Binormal is calculated from normal and tangent. Just like normal or tangent, it needs to be scaled and biased into a displayable 0..1 range.

Shader "Debug/Binormals" {
SubShader {
    Pass {
        Fog { Mode Off }
        CGPROGRAM

        #pragma vertex vert
        #pragma fragment frag

        // vertex input: position, normal, tangent
        struct appdata {
            float4 vertex : POSITION;
            float3 normal : NORMAL;
            float4 tangent : TANGENT;
        };

        struct v2f {
            float4 pos : SV_POSITION;
            float4 color : COLOR;
        };
        
        v2f vert (appdata v) {
            v2f o;
            o.pos = mul( UNITY_MATRIX_MVP, v.vertex );
            // calculate binormal
            float3 binormal = cross( v.normal, v.tangent.xyz ) * v.tangent.w;
            o.color.xyz = binormal * 0.5 + 0.5;
            o.color.w = 1.0;
            return o;
        }
        
        fixed4 frag (v2f i) : SV_Target { return i.color; }
        ENDCG
    }
}
}