Demo 20 - Distort with grab pass

Shader "Custom/DistortingGrabPass" {
    Properties {
        _Intensity ("Intensity", Range(0, 50)) = 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 _Intensity;

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

            half4 frag(v2f i) : COLOR {
                i.grabPos.x += sin((_Time.y + i.grabPos.y) * _Intensity)/20;
                fixed4 color = tex2Dproj(_GrabTexture, UNITY_PROJ_COORD(i.grabPos));
                return color;
            }
            ENDCG
        }
    }
    FallBack "Diffuse"