Gradient shader not works?

Unity Engine
1

Hi.

Why this bottom shader code is not working? I want to make a vertical gradient shader for mobile phones. I see only one color when I use it e.g. on a quad object.

Shader "Custom/BasicGradient"
{
Properties
{
     _TopColor ("Top Color", Color) = (1, 1, 1, 1)
     _BottomColor ("Bottom Color", Color) = (1, 1, 1, 1)
     _RampTex ("Ramp Texture", 2D) = "white" {}
}
SubShader
{
     Pass
     {
         Blend SrcAlpha OneMinusSrcAlpha
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         struct vertexIn {
             float4 pos : POSITION;
             float2 uv : TEXCOORD0;
         };
         struct v2f {
             float4 pos : SV_POSITION;
             float2 uv : TEXCOORD0;
         };
         v2f vert(vertexIn input)
         {
             v2f output;
             output.pos = mul(UNITY_MATRIX_MVP, input.pos);
             output.uv = input.uv;
             return output;
         }
         fixed4 _TopColor, _BottomColor;
         sampler2D _RampTex;
         fixed4 frag(v2f input) : COLOR
         {
             return lerp(_BottomColor, _TopColor, tex2D(_RampTex, input.uv).a);
         }
         ENDCG
     }
}
2

Nothing obviously wrong with the shader, what’s the texture you’re using for the ramp, and do you need it?

Why not just:

Shader "Custom/BasicGradient"
{
Properties
{
     _TopColor ("Top Color", Color) = (1, 1, 1, 1)
     _BottomColor ("Bottom Color", Color) = (1, 1, 1, 1)
}
SubShader
{
     Pass
     {
         Blend SrcAlpha OneMinusSrcAlpha
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         struct vertexIn {
             float4 pos : POSITION;
             float2 uv : TEXCOORD0;
         };
         struct v2f {
             float4 pos : SV_POSITION;
             float2 uv : TEXCOORD0;
         };
         v2f vert(vertexIn input)
         {
             v2f output;
             output.pos = mul(UNITY_MATRIX_MVP, input.pos);
             output.uv = input.uv;
             return output;
         }
         fixed4 _TopColor, _BottomColor;
         fixed4 frag(v2f input) : COLOR
         {
             return lerp(_BottomColor, _TopColor, input.uv.y);
         }
         ENDCG
     }
}