Shader "VFX/FresnelShading"
{
    Properties
    {
    //Color of the sphere. Fadeout is an extra modifier for fade agressiveness.
        _Color ("Color", Color) = (1,1,1,1)
        _Fadeout ("Fadeout", Float) = 4
    }
    SubShader
    {
    //Enable transparency:
        Tags { "Queue"="Transparent" "RenderType"="Transparent" }
        ZWrite Off
        Blend SrcAlpha OneMinusSrcAlpha

    //Only one pass needed:
        Pass
        {
            CGPROGRAM

            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            fixed4 _Color;
            half _Fadeout;

            //We need position and color by default.
            struct VertShaderOutput
            {
                float4 Position : SV_POSITION;
                fixed4 color : COLOR0;
            };

            VertShaderOutput vert (appdata_base v)
            {
                VertShaderOutput o;
                o.Position = mul (UNITY_MATRIX_MVP, v.vertex);

                //Here we calculate intensity of the color. Closer to the edge, more intensity:
                float intensity;

                float3 direction = normalize(WorldSpaceViewDir(v.vertex));
                intensity = 1 / dot(direction, v.normal);

                //Color by intensity
                o.color = (_Color * intensity);

                //Alpha is intensity itself, plus modified a bit by the fade.
                o.color.a = intensity / _Fadeout;
                return o;

            }

            fixed4 frag (VertShaderOutput input) : SV_Target
            {
            //Finally, return color modified by Color's Alpha (modified by script).
                return input.color * _Color.a;
            }

            ENDCG
        }
    }
    FallBack "Diffuse"
}