Unity shader之ColorMask

時間 2019-12-06

標籤 unity shader colormask 简体版

原文原文鏈接

Color Mask解釋，見unity文檔：html

ColorMask

ColorMask RGB | A | 0 | any combination of R, G, B, A

Set color channel writing mask. Writing ColorMask 0 turns off rendering to all color channels. Default mode is writing to all channels (RGBA), but for some special effects you might want to leave certain channels unmodified, or disable color writes completely.app

When using multiple render target (MRT) rendering, it is possible to set up different color masks for each render target, by adding index (0–7) at the end. For example, ColorMask RGB 3 would make render target #3 write only to RGB channels.ide

以下面問題，這是經過RenderTexture渲染了一個粒子，掛在NGUI的UITexture中。spa

但願去掉黑色區域而徹底展示背景顏色，可經過ColorMask解決。code

攝像機顏色爲：htm

粒子shader爲：blog

 1 Shader "effect/distortadd Lv3"
 2 {
 3     Properties
 4     {
 5         _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
 6         _NoiseTex ("Distort Texture (RG)", 2D) = "white" {}
 7         _MainTex ("Alpha (A)", 2D) = "white" {}
 8         _HeatTime  ("Heat Time", range (-1,1)) = 0
 9         _ForceX  ("Strength X", range (0,1)) = 0.1
10         _ForceY  ("Strength Y", range (0,1)) = 0.1
11     }
12 
13     Category
14     {
15         Tags { "Queue"="Transparent+400" "RenderType"="Transparent" }
16         Blend SrcAlpha One
17         Cull Off Lighting Off ZWrite Off Fog { Color (0,0,0,0) }
18         BindChannels
19         {
20             Bind "Color", color
21             Bind "Vertex", vertex
22             Bind "TexCoord", texcoord
23         }
24 
25         SubShader
26         {
27             Pass
28             {
29                 CGPROGRAM
30                 #pragma vertex vert
31                 #pragma fragment frag
32                 #pragma fragmentoption ARB_precision_hint_fastest
33                 #pragma multi_compile_particles
34                 #include "UnityCG.cginc"
35 
36                 struct appdata_t
37                 {
38                     float4 vertex : POSITION;
39                     fixed4 color : COLOR;
40                     float2 texcoord: TEXCOORD0;
41                 };
42 
43                 struct v2f
44                 {
45                     float4 vertex : POSITION;
46                     fixed4 color : COLOR;
47                     float2 uvmain : TEXCOORD1;
48                 };
49 
50                 fixed4 _TintColor;
51                 fixed _ForceX;
52                 fixed _ForceY;
53                 fixed _HeatTime;
54                 float4 _MainTex_ST;
55                 float4 _NoiseTex_ST;
56                 sampler2D _NoiseTex;
57                 sampler2D _MainTex;
58 
59                 v2f vert (appdata_t v)
60                 {
61                     v2f o;
62                     o.vertex = UnityObjectToClipPos(v.vertex);
63                     o.color = v.color;
64                     o.uvmain = TRANSFORM_TEX( v.texcoord, _MainTex );
65                     return o;
66                 }
67 
68                 fixed4 frag( v2f i ) : COLOR
69                 {
70                     //noise effect
71                     fixed4 offsetColor1 = tex2D(_NoiseTex, i.uvmain + _Time.xz*_HeatTime);
72                     fixed4 offsetColor2 = tex2D(_NoiseTex, i.uvmain + _Time.yx*_HeatTime);
73                     i.uvmain.x += ((offsetColor1.r + offsetColor2.r) - 1) * _ForceX;
74                     i.uvmain.y += ((offsetColor1.r + offsetColor2.r) - 1) * _ForceY;
75                     return 2.0f * i.color * _TintColor * tex2D( _MainTex, i.uvmain);
76                 }
77                 ENDCG
78             }
79         }
80         // ------------------------------------------------------------------
81         // Fallback for older cards and Unity non-Pro
82         
83         SubShader
84         {
85             Blend DstColor Zero
86             Pass
87             {
88                 Name "BASE"
89                 SetTexture [_MainTex] {    combine texture }
90             }
91         }
92     }
93 }

View Code

shader使用圖片爲：圖片

NGUI中 UITexture使用的shader爲：ip

 1 Shader "Unlit/Premultiplied Colored"
 2 {
 3     Properties
 4     {
 5         _MainTex ("Base (RGB), Alpha (A)", 2D) = "black" {}
 6     }
 7 
 8     SubShader
 9     {
10         LOD 200
11 
12         Tags
13         {
14             "Queue" = "Transparent"
15             "IgnoreProjector" = "True"
16             "RenderType" = "Transparent"
17         }
18 
19         Pass
20         {
21             Cull Off
22             Lighting Off
23             ZWrite Off
24             AlphaTest Off
25             Fog { Mode Off }
26             Offset -1, -1
27             ColorMask RGB
28             Blend One OneMinusSrcAlpha
29         
30             CGPROGRAM
31             #pragma vertex vert
32             #pragma fragment frag
33             #include "UnityCG.cginc"
34 
35             sampler2D _MainTex;
36             float4 _MainTex_ST;
37 
38             struct appdata_t
39             {
40                 float4 vertex : POSITION;
41                 float2 texcoord : TEXCOORD0;
42                 half4 color : COLOR;
43             };
44 
45             struct v2f
46             {
47                 float4 vertex : POSITION;
48                 float2 texcoord : TEXCOORD0;
49                 half4 color : COLOR;
50             };
51 
52             v2f vert (appdata_t v)
53             {
54                 v2f o;
55                 o.vertex = UnityObjectToClipPos(v.vertex);
56                 o.texcoord = v.texcoord;
57                 o.color = v.color;
58                 return o;
59             }
60 
61             half4 frag (v2f IN) : COLOR
62             {
63                 half4 col = tex2D(_MainTex, IN.texcoord) * IN.color;
64                 return col;
65             }
66             ENDCG
67         }
68     }
69     
70     SubShader
71     {
72         LOD 100
73 
74         Tags
75         {
76             "Queue" = "Transparent"
77             "IgnoreProjector" = "True"
78             "RenderType" = "Transparent"
79         }
80         
81         Pass
82         {
83             Cull Off
84             Lighting Off
85             ZWrite Off
86             AlphaTest Off
87             Fog { Mode Off }
88             Offset -1, -1
89             ColorMask RGB
90             Blend One OneMinusSrcAlpha 
91             ColorMaterial AmbientAndDiffuse
92             
93             SetTexture [_MainTex]
94             {
95                 Combine Texture * Primary
96             }
97         }
98     }
99 }

View Code

只因此出現黑色，這裏有兩層混合，一層是攝像機中此粒子與攝像機默認顏色，由於此shader渲染出來的顏色就是黑色（見圖片顏色），alpha也全爲1，再經過Blend SrcAlpha One命令混合，而目標顏色爲黑色，alpha爲0（見攝像機顏色），所以這一層混合後只剩下圖片的顏色。ci

第二層混合在NGUI的UITexture中，此UITexture使用shader的混合命令爲：Blend One OneMinusSrcAlpha，因爲srcAlpha一直爲1，因此UITexture後面的背景顏色在混合中消失了，渲染出來的結果只剩下圖片的顏色。

要想去除黑色，能夠經過 ColorMask RGB來屏蔽此通道輸出的alpha，而徹底取攝像機的alpha（即爲0）。見shader代碼：

此時效果以下：

轉載請註明出處：http://www.javashuo.com/article/p-dgbiqzjg-gw.html

之因此ColorMask會解決這個問題，是由於ColorMask和Blend命令的執行前後順序，先Blend，再ColorMask，這樣Blend時使用frag shader中輸出的alpha，保持了rgb顏色的正常，再color mask，屏蔽alpha通道，此時會去取攝像機的alpha，即爲0。

而UITexture使用shader的混合命令爲：Blend One OneMinusSrcAlpha，因此黑色在混合時消失了，其它顏色保留下來了，且能與背景很好地融合。

資源以下：

https://files.cnblogs.com/files/jietian331/ColorMask.zip