1.代码

Shader "Custom/VertColor1"
{

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

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

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

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

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                if(o.vertex.x < 0.5){
                    o.color = float4(1,0,0,1);
                }else{
                    o.color = float4(0,0,1,1);
                }
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {

                return i.color;
            }
            ENDCG
        }
    }
}

效果:

2.裁剪坐标系

Shader "Custom/VertColor1"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

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

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

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                o.color = float4(o.vertex.x,0,0,1);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {

                return i.color;
            }
            ENDCG
        }
    }
}

效果:

3.世界坐标
绝对坐标，物体一动就失效了，一般不用。

Shader "Custom/VertColor1"
{
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

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

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

            v2f vert (appdata v)
            {
                v2f o;
                // 使用UNITY_MATRIX_M将模型空间顶点转换到世界空间
                float4 worldPos = mul(UNITY_MATRIX_M, v.vertex);
                if(length(worldPos.xy - float2(-5,-5)) < 1e-6){
                    o.color = float4(1,0,0,1);
                }else if(length(worldPos.xy - float2(5,5)) < 1e-6){
                    o.color = float4(0,0,1,1);
                }else if(length(worldPos.xy - float2(-5,5)) < 1e-6){
                    o.color = float4(0,1,1,1);
                }else if(length(worldPos.xy - float2(5,-5)) < 1e-6){
                    o.color = float4(0,1,0,1);
                }
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {

                return i.color;
            }
            ENDCG
        }
    }
}

效果: