Resizing a projector and tiling texture?

Hey, try using this

Shader "Projector/Caustics" {

 Properties {
    _Color ("Color", Color) = (1,1,1,0)
    _ShadowTex ("Cookie", 2D) = "black" { TexGen ObjectLinear }
    _Size ("Grid Size", Float) = 1
 }
 
 Subshader {
    Tags { "RenderType"="Transparent" "Queue"="Transparent+100" }
    Pass {
      ZWrite Off
      Offset -1, -1
      Fog { Mode Off }
      //ColorMask RGB
      //Blend SrcAlpha OneMinusSrcAlpha
      Blend DstColor One

 
      CGPROGRAM
      #pragma vertex vert
      #pragma fragment frag
      #pragma fragmentoption ARB_fog_exp2
      #pragma fragmentoption ARB_precision_hint_fastest
      #include "UnityCG.cginc"
 
      struct v2f {
       float4 pos : SV_POSITION;
       float2 uv : TEXCOORD0;
      };
 
      uniform sampler2D _ShadowTex;
      float4 _ShadowTex_ST;
      float4 _Color;
      float4x4 _Projector;
      fixed _Size;
 
      v2f vert (appdata_tan v) {
       v2f o;
       o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
       o.uv = TRANSFORM_TEX (mul (_Projector, v.vertex).xy, _ShadowTex);
       return o;
      }
 
      fixed4 frag (v2f i) : COLOR {
       if (i.uv.x < 1 && i.uv.y < 1)
           return tex2D (_ShadowTex, fmod (i.uv, 1 / _Size) * _Size) * _Color;
       else
           return fixed4 (0,0,0,0);
      }
 
      ENDCG
    }
 }

}

I just modified it slightly from this script developed here on this thread: http://answers.unity3d.com/questions/520207/projector-repeating-texture-using-custom-shader.html

It works fairly well for orthographic caustics.