Demo 49 - Spotlight

Shader "Custom/Spotlight"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _CenterX ("Center X", Range(0.0, 0.5)) = 0.25
        _CenterY ("Center Y", Range(0.0, 0.5)) = 0.25
        _Radius ("Radius", Range(0.01, 0.5)) = 0.1
        _Sharpness ("Sharpness", Range(1, 20)) = 1
    }
    SubShader
    {
        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag
            #include "UnityCG.cginc"

            sampler2D _MainTex;
            float _CenterX, _CenterY;
            float _Radius;
            float _Sharpness;

            fixed4 frag (v2f_img i) : SV_Target
            {
                float dist = distance(float2(_CenterX, _CenterY), ComputeScreenPos(i.pos).xy / _ScreenParams.x);
                fixed4 col = tex2D(_MainTex, i.uv);
                return col * (1 - pow(dist / _Radius, _Sharpness));
            }

            ENDCG
        }
    }
}