Shader-水流效果

效果图：（贴图类似于泥石流）

代码：

 Shader "CookbookShaders/Chapter02/ScrollingUVs"
 {
     Properties
     {
         _MainTint("Diffuse Tint", Color) = (,,,)
         _MainTex("Base (RGB)", 2D) = "white" {}
         _ScrollXSpeed("X Scroll Speed", Range(, )) =
         _ScrollYSpeed("Y Scroll Speed", Range(, )) =
     }

         SubShader
     {
         Tags{ "RenderType" = "Opaque" }
         LOD 

         CGPROGRAM
 #pragma surface surf Lambert

     fixed4 _MainTint;
     fixed _ScrollXSpeed;
     fixed _ScrollYSpeed;
     sampler2D _MainTex;

     struct Input
     {
         float2 uv_MainTex;
     };

     void surf(Input IN, inout SurfaceOutput o)
     {
         //Create a seperate variable to store our uvs
         //before we pass them to the tex2D() function
         fixed2 scrolledUV = IN.uv_MainTex;

         //Create variables that store the individual x and y
         //components for the uv's scaled by time
         fixed xScrollValue = _ScrollXSpeed * _Time;
         fixed yScrollValue = _ScrollYSpeed * _Time;

         //Apply the final uv offset
         scrolledUV += fixed2(xScrollValue, yScrollValue);

         //Apply textures and tint
         half4 c = tex2D(_MainTex, scrolledUV);
         o.Albedo = c.rgb * _MainTint;
         o.Alpha = c.a;
     }
     ENDCG
     }
         FallBack "Diffuse"
 }

注意：

内置方法 _Time

是个4维向量，跟Unity3D中的deltaTime（这是个一维的，数值）不同。

• float4 _Time : Time (t/20, t, t*2, t*3), use to animate things inside the shaders