Shader "Unity Shaders Book/Chapter 11/Image Sequence Animation" {
	Properties {
		_Color ("Color Tint", Color) = (1, 1, 1, 1)
		_MainTex ("Image Sequence", 2D) = "white" {}
    	_HorizontalAmount ("Horizontal Amount", Float) = 4
    	_VerticalAmount ("Vertical Amount", Float) = 4
    	_Speed ("Speed", Range(1, 100)) = 30
	}
	SubShader {
		Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
		
		Pass {
			Tags { "LightMode"="ForwardBase" }
			
			ZWrite Off
			Blend SrcAlpha OneMinusSrcAlpha
			
			CGPROGRAM
			
			#pragma vertex vert  
			#pragma fragment frag
			
			#include "UnityCG.cginc"
			
			fixed4 _Color;
			sampler2D _MainTex;
			float4 _MainTex_ST;
			float _HorizontalAmount;
			float _VerticalAmount;
			float _Speed;
			  
			struct a2v {  
			    float4 vertex : POSITION; 
			    float2 texcoord : TEXCOORD0;
			};  
			
			struct v2f {  
			    float4 pos : SV_POSITION;
			    float2 uv : TEXCOORD0;
			};  
			
			v2f vert (a2v v) {  
				v2f o;  
				o.pos = UnityObjectToClipPos(v.vertex);  
				o.uv = TRANSFORM_TEX(v.texcoord, _MainTex);  
				return o;
			}  
			
			fixed4 frag (v2f i) : SV_Target {
				float time = floor(_Time.y * _Speed);  
				float row = floor(time / _HorizontalAmount);
				float column = time - row * _HorizontalAmount;
				
				half2 uv = i.uv + half2(column, -row);
				uv.x /=  _HorizontalAmount;
				uv.y /= _VerticalAmount;
				
				fixed4 c = tex2D(_MainTex, uv);
				c.rgb *= _Color;
				
				return c;
			}
			
			ENDCG
		}  
	}
	FallBack "Transparent/VertexLit"
}

代码如上，对于frag里的计算部分

1.这句 

half2 uv = i.uv + half2(column, -row);

这里如果去掉i.uv会怎么样，

2.这两句

uv.x /=  _HorizontalAmount;
uv.y /= _VerticalAmount;

首先想问下，这里的/=是和c#里的/=一样吧

还有，shader里这个frag是每帧都调用吗，如果是的话，这个uv的x和y不是一直在除。。。那得到的值也就不对了啊

3.没了。。。