1.shader代码
视口坐标范围 : [-1,1]

Shader "Custom/VertColorClipPos"
{
    Properties
    {

    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
                fixed4 vcol : COLOR;
            };


            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                float x = o.vertex.x / o.vertex.w;
                if(x <= -1)
                {
                    o.vcol = fixed4(1,0,0,1);
                }
                else if(x >= 1)
                {
                    o.vcol = fixed4(0,0,1,1);
                }
                else
                {
                    float xx = x / 2 + 0.5;
                    o.vcol = fixed4(xx,xx,xx,1);
                }
                return o;
            }

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

2.Cube例子
x坐标越接近左边越暗，越接近右边越亮

3.quad例子