What is wrong with my shader?

Questions & Answers
1

I have a shader which essentially is meant to make an animated gradient. I made a texture which is a square with an alpha gradient towards the centre. The shader reads this texture and only displays pixels which have an alpha value above _Cutout. _Cutout is edited by a script.

Shader “Unlit/RadialSprite”
{
Properties
{
_MainTex (“Texture”, 2D) = “white” {}
_Color (“Color”, Color) = 1, 1, 1, 1
_Cutout (“Cutout”, Range(0, 1)) = 0.5
}
SubShader
{
// Treat this material as transparent
Tags { “RenderType”=“Transparent” “Queue”=“Transparent” “IgnoreProjector”=“True” }
LOD 100

    // Set up alpha blending
    ZWrite Off
    Blend SrcAlpha OneMinusSrcAlpha

    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;
        };

        sampler2D _MainTex;
        float4 _MainTex_ST;
        // Add shader variables for our material properties.
        fixed4 _Color;
        float _Cutout;

        v2f vert (appdata v)
        {
            v2f o;
            o.vertex = UnityObjectToClipPos(v.vertex);
            o.uv = TRANSFORM_TEX(v.uv, _MainTex);
            return o;
        }

        fixed4 frag (v2f i) : SV_Target
        {
            fixed4 col = tex2D(_MainTex, i.uv);

            // Hide any part of the image that's darker than 
            // the current alpha value of the particle color
            col.a = saturate((col.r -_Cutout) * 10.0f);

            // Replace the visible color of the image
            // with the material color
            col.rgb = _Color.rgb;

            return col;
        }
        ENDCG
    }
}

}

My problem is that when I put the texture on the material, the entire quad goes white, my texure doesnt appear.

2

That’s because just before you output a colour, you overwrite the texture with the primary material colour;

//This;
col.rgb = _Color.rgb;

//Should be this;
col.rgb = col.rgb * _Color.rgb;