1 Shader "MyShader/SnowShader" {
 2     Properties{
 3         _MainTex("MainTex",2D)="white"{}//纹理
 4         _SnowNum("Snow Num",Range(-1,1))=0//点乘阀值
 5         _SnowIntensity("Snow Intensity",Range(0,20))=1//积雪强度
 6         _SnowColor("Snow Color",Color)=(1.0,1.0,1.0,1.0)//积雪颜色
 7     }
 8 
 9     SubShader{
10         Pass{
11             Tags{"LightMode"="ForwardBase"}
12             CGPROGRAM
13             #pragma vertex vert
14             #pragma fragment frag
15             #include "UnityCG.cginc"
16 
17                 sampler2D _MainTex;
18                 float4 _MainTex_ST;
19                 fixed _SnowNum;
20                 fixed _SnowIntensity;
21                 fixed4 _SnowColor;
22 
23                 struct a2v{
24                     float4 vertex:POSITION;
25                     float3 normal:NORMAL;
26                     float2 texcoord:TEXCOORD0;
27                 };
28 
29                 struct v2f{
30                     float4 pos:SV_POSITION;
31                     float3 worldNormal:TEXCOORD0;
32                     float2 uv:TEXCOORD1;
33                 };
34 
35                 v2f vert(a2v v){    
36                     v2f o;
37                     o.pos=mul(UNITY_MATRIX_MVP,v.vertex);
38                     o.worldNormal=UnityObjectToWorldNormal(v.normal);
39                     o.uv=v.texcoord*_MainTex_ST.xy+_MainTex_ST.zw;
40                     return o;
41                 }
42 
43                 fixed4 frag(v2f i):SV_TARGET{
44                     fixed3 tex=tex2D(_MainTex,i.uv).rgb;
45                     fixed3 worldNormalDir=normalize(i.worldNormal);
46                     fixed3 worldUpDir=fixed3(0,1,0);
47                     //用smoothstep是为了使得积雪边缘过渡更平滑
48                     fixed colNum=smoothstep(_SnowNum,1,dot(worldNormalDir,worldUpDir))*_SnowIntensity;
49                     //fixed colNum=step(dot(worldNormalDir,worldUpDir),_SnowNum);
50                     fixed3 finalCol=lerp(tex,_SnowColor,colNum);
51                     return fixed4(finalCol,1);
52                 }
53             ENDCG
54         }
55     }
56     FallBack "Diffuse"
57 }