Demo 14 - Misc with grab pass

Shader "Custom/Grab pass" {
    Properties {
        _ZoomVal ("Zoom value", Range(0, 20)) = 0
    }
    SubShader {
        GrabPass { "_GrabTexture" }

        Pass {
            Tags { "Queue"="Transparent" }

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

            struct v2f {
                half4 pos : SV_POSITION;
                half4 grabPos : TEXCOORD0;
            };

            sampler2D _GrabTexture;
            half _ZoomVal;

            v2f vert(appdata_base v) {
                v2f o;
                o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
                o.grabPos = ComputeGrabScreenPos(o.pos + half4(0, 0, 0, _ZoomVal));
                return o;
            }

            half4 frag(v2f i) : COLOR {
                fixed4 color = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.grabPos));
                fixed val = (color.x  + color.y + color.z) / 3;
                return fixed4(val, val, val, color.a);
            }
            ENDCG
        }
    }
    FallBack "Diffuse"
}