unity_shader之实现场景淡入淡出

3D游戏中经常会用到往前走场景的淡入效果，实际就是物体从透明逐渐变实的过程
用Shader实现非常简单

实现思路：
1 设置淡入的起始距离 和 结束距离
2 在vertex阶段计算物体顶点与相机的距离
3 根据距离计算alpha

Shader如下
 

1. Shader "Custom/Fade" {
2.     Properties {
3.         _MainTex ("Texture", 2D) = "white" { }
4.         _FadeDistanceNear ("Near fadeout dist (View Space)", float) = 35    
5.         _FadeDistanceFar ("Far fadeout dist (View Space)", float) = 40
6.     }
7.     SubShader
8.     {
9.         Tags { "Queue"="Transparent" "RenderType"="Transparent"}
10.         ZWrite On
11.         Blend SrcAlpha OneMinusSrcAlpha
12.         pass
13.         {
14.             CGPROGRAM
15.             #pragma vertex vert
16.             #pragma fragment frag
17.             #include "UnityCG.cginc"
18.             sampler2D _MainTex;
19.             float4 _MainTex_ST;
20.             struct v2f {
21.                 float4  pos : SV_POSITION;
22.                 float2  uv : TEXCOORD0;
23.                 float fade:TEXCOORD1;
24.             } ;
25.             float _FadeDistanceNear;
26.             float _FadeDistanceFar;
27.             v2f vert (appdata_base v)
28.             {
29.                 v2f o;
30.                 o.pos = mul(UNITY_MATRIX_MVP,v.vertex);
31.                 o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
32.                 //相机坐标系的物体坐标
33.                 float3 posView = mul(UNITY_MATRIX_MV,v.vertex).xyz;
34.                 //计算与相机距离
35.                 float dis = length(posView);
36.                 //计算fade
37.                 o.fade = 1 - saturate((dis - _FadeDistanceNear)/(_FadeDistanceFar - _FadeDistanceNear));
38.                 return o;
39.             }
40.             float4 frag (v2f i) : COLOR
41.             {
42.                 float4 texCol = tex2D(_MainTex,i.uv);
43.                 float4 outp = texCol;
44.                 //fade作为alpha
45.                 return float4(outp.rgb,i.fade);
46.             }
47.             ENDCG
48.         }
49.     }
50. }

 

转载自风宇冲新浪博客