where to assign this shader varible?

Questions & Answers
1

where to assign this shader varible?

I have recently used ImageEffect, i.e. Blur.
But I cannot figure out how the “_BlurOffsets” varible is assigned or be used?
Does anybody know how that shader work?

CGINCLUDE
	#include "UnityCG.cginc"
	struct v2f {
		float4 pos : POSITION;
		half2 uv : TEXCOORD0;
		half2 taps[4] : TEXCOORD1; 
	};
	sampler2D _MainTex;
	half4 _MainTex_TexelSize;
	half4 _BlurOffsets;
	v2f vert( appdata_img v ) {
		v2f o; 
		o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
		o.uv = v.texcoord - _BlurOffsets.xy * _MainTex_TexelSize.xy; // hack, see BlurEffect.cs for the reason for this. let's make a new blur effect soon
		o.taps[0] = o.uv + _MainTex_TexelSize * _BlurOffsets.xy;
		o.taps[1] = o.uv - _MainTex_TexelSize * _BlurOffsets.xy;
		o.taps[2] = o.uv + _MainTex_TexelSize * _BlurOffsets.xy * half2(1,-1);
		o.taps[3] = o.uv - _MainTex_TexelSize * _BlurOffsets.xy * half2(1,-1);
		return o;
	}
	half4 frag(v2f i) : COLOR {
		half4 color = tex2D(_MainTex, i.taps[0]);
		color += tex2D(_MainTex, i.taps[1]);
		color += tex2D(_MainTex, i.taps[2]);
		color += tex2D(_MainTex, i.taps[3]); 
		return color * 0.25;
	}
	ENDCG
3

_BlurOffsets is assigned when you used graphics.BlitMultiTap 's offset feature. For example, when you do Graphics.BlitMultiTap(source, dest, mtl, new Vector(-4,5)); _BlurOffsets.xy will be assigned to (-4,5).

see this research (in Chinese):

http://game.ceeger.com/forum/read.php?tid=3450&fid=2&page=1

2

In a MonoBehaviour Script:

renderer.sharedMaterial.SetVector("_BlurOffsets", new Vector3(x, y, z));