Unity Shader之模板测试

一、Stencil testing

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    当片段着色器处理完一个片段之后，模板测试(Stencil Test)会开始执行，和深度测试一样，它也可能会丢弃片段。接下来，被保留的片段会进入深度测试，它可能会丢弃更多的片段。模板测试是根据又一个缓冲来进行的，它叫做模板缓冲(Stencil Buffer)，我们可以在渲染的时候更新它来获得一些很有意思的效果。
    一个模板缓冲中，（通常）每个模板值(Stencil Value)是8位的。所以每个像素/片段一共能有256种不同的模板值。我们可以将这些模板值设置为我们想要的值，然后当某一个片段有某一个模板值的时候，我们就可以选择丢弃或是保留这个片段了。

二、模板函数

2.1 调用函数

1. Stencil 
   

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2. ｛ 
   

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3. Ref 1//Reference Value ReadMask 255 WriteMask 255 Comp Always //Comparison Function Pass Replace 
   

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4. Fail Keep 
   

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5. ZFail Replace 
   

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6. ｝ 
   

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2.2 参数说明

Ref :就是参考值，当参数允许赋值时，会把参考值赋给当前像素
ReadMask: 对当前参考值和已有值进行mask操作，默认值255，一般不用
WriteMask: 写入Mask操作，默认值255，一般不用

Comp: 比较方法。是拿Ref参考值和当前像素缓存上的值进行比较。默认值always，即一直通过。
-- Greater - 大于

• GEqual - 大于等于
• Less - 小于
• LEqual - 小于等于
• Equal - 等于
• NotEqual - 不等于
• Always - 永远通过
• Never - 永远通不过

Pass: 当模版测试和深度测试都通过时，进行处理

Fail :当模版测试和深度测试都失败时，进行处理

ZFail: 当模版测试通过而深度测试失败时，进行处理

pass，Fail，ZFail都属于Stencil操作，他们参数统一如下：

• Keep 保持(即不把参考值赋上去，直接不管)
• Zero 归零
• Replace 替换(拿参考值替代原有值)
• IncrSat 值增加1，但不溢出，如果到255，就不再加
• DecrSat 值减少1，但不溢出，值到0就不再减
• Invert 反转所有位，如果1就会变成254
• IncrWrap 值增加1，会溢出，所以255变成0
• DecrWrap 值减少1，会溢出，所以0变成255

三、案例

3.1 描边

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1. Shader "ShaderCookbook/stencil_outline" { 
   

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2. Properties { 
   

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3. _MainTex("Texture", 2D) = "white" {} 
   

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4. _OutLineWidth("Width", float) = 0.01  
   

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5. _OutLineColor("Color", color) = (1, 1, 1, 1) 
   

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6. } 
   

   ---

7. SubShader { 
   

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8. Tags { 
   

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9. "RenderType" = "Opaque" 
   

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10. } 
    

    ---

11. LOD 100 
    

    ---

12. ---

13. Stencil { 
    

    ---

14. Ref 0 Comp Equal Pass IncrSat 
    

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15. } 
    

    ---

16. ---

17. Pass { 
    

    ---

18. CGPROGRAM 
    

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19. #pragma vertex vert 
    

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20. #pragma fragment frag 
    

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21. #include "UnityCG.cginc" 
    

    ---

22. ---

23. struct appdata { 
    

    ---

24. float4 vertex: POSITION; 
    

    ---

25. float2 uv: TEXCOORD0; 
    

    ---

26. }; 
    

    ---

27. ---

28. struct v2f { 
    

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29. float2 uv: TEXCOORD0; 
    

    ---

30. float4 vertex: SV_POSITION; 
    

    ---

31. }; 
    

    ---

32. ---

33. sampler2D _MainTex; 
    

    ---

34. float4 _MainTex_ST; 
    

    ---

35. v2f vert(appdata v) { 
    

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36. v2f o; 
    

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37. o.vertex = UnityObjectToClipPos(v.vertex); 
    

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38. o.uv = TRANSFORM_TEX(v.uv, _MainTex); 
    

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39. return o; 
    

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40. } 
    

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41. fixed4 frag(v2f i) : SV_Target { 
    

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42. // sample the texture 
    

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43. fixed4 col = tex2D(_MainTex, i.uv); 
    

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44. return col; 
    

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45. } 
    

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46. ENDCG 
    

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47. } 
    

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48. ---

49. Pass { 
    

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50. CGPROGRAM 
    

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51. #pragma vertex vert 
    

    ---

52. #pragma fragment frag 
    

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53. ---

54. struct appdata { 
    

    ---

55. float4 vertex: POSITION; 
    

    ---

56. float4 normal: NORMAL; 
    

    ---

57. }; 
    

    ---

58. ---

59. struct v2f { 
    

    ---

60. float4 vertex: SV_POSITION; 
    

    ---

61. }; 
    

    ---

62. ---

63. fixed4 _OutLineColor; 
    

    ---

64. float _OutLineWidth; 
    

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65. v2f vert(appdata v) { 
    

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66. v2f o; 
    

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67. v.vertex = v.vertex + normalize(v.normal) * _OutLineWidth; 
    

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68. o.vertex = UnityObjectToClipPos(v.vertex); 
    

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69. return o; 
    

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70. } 
    

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71. fixed4 frag(v2f i) : SV_Target { 
    

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72. // sample the texture 
    

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73. fixed4 col = _OutLineColor; 
    

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74. return col; 
    

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75. } 
    

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76. ENDCG 
    

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77. } 
    

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78. } 
    

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79. } 
    

    ---

3.2 百宝箱

渲染管线

遮罩层：

1. Shader "ShaderCookbook/StencilEnumMask" 
   

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2. { 
   

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3. Properties 
   

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4. { 
   

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5. _MainTex ("Texture", 2D) = "white" {} 
   

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6. [ForceInt] 
   

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7. _StencilRef("StencilRef",float) = 0 
   

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8. [Enum(UnityEngine.Rendering.CompareFunction)] 
   

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9. _StencilComp("StencilComp",int) =0 
   

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10. [Enum(UnityEngine.Rendering.StencilOp)] 
    

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11. _StencilOp("StencilOp",int)=0 
    

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12. ---

13. [ForceInt] 
    

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14. _StencilReadMask("ReadMask",int)=255 
    

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15. [ForceInt] 
    

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16. _StencilWriteMask("WriteMask",int)=255 
    

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17. [MaterialToggle] 
    

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18. _ZWrite("zWrite",float)=0 
    

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19. } 
    

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20. SubShader 
    

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21. { 
    

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22. Tags { "RenderType"="StencilMaskOpaque" 
    

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23. "Queue" = "Geometry-100" 
    

    ---

24. "IgnoreProjector" = "True" } 
    

    ---

25. LOD 100 
    

    ---

26. ---

27. ---

28. Pass 
    

    ---

29. { 
    

    ---

30. ColorMask 0 
    

    ---

31. ZWrite [_ZWrite] 
    

    ---

32. ---

33. Stencil{ 
    

    ---

34. Ref [_StencilRef] 
    

    ---

35. Comp[_StencilComp] 
    

    ---

36. Pass[_StencilOp] 
    

    ---

37. ReadMask[_StencilReadMask] 
    

    ---

38. WriteMask[_StencilWriteMask] 
    

    ---

39. } 
    

    ---

40. ---

41. CGPROGRAM 
    

    ---

42. #pragma vertex vert 
    

    ---

43. #pragma fragment frag 
    

    ---

44. // make fog work 
    

    ---

45. #pragma multi_compile_fog 
    

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46. #include "UnityCG.cginc" 
    

    ---

47. ---

48. ---

49. struct appdata 
    

    ---

50. { 
    

    ---

51. float4 vertex : POSITION; 
    

    ---

52. float2 uv : TEXCOORD0; 
    

    ---

53. }; 
    

    ---

54. ---

55. struct v2f 
    

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56. { 
    

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57. float2 uv : TEXCOORD0; 
    

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58. UNITY_FOG_COORDS(1) 
    

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59. float4 vertex : SV_POSITION; 
    

    ---

60. }; 
    

    ---

61. ---

62. sampler2D _MainTex; 
    

    ---

63. float4 _MainTex_ST; 
    

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64. v2f vert (appdata v) 
    

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65. { 
    

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66. v2f o; 
    

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67. o.vertex = UnityObjectToClipPos(v.vertex); 
    

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68. o.uv = TRANSFORM_TEX(v.uv, _MainTex); 
    

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69. UNITY_TRANSFER_FOG(o,o.vertex); 
    

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70. return o; 
    

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71. } 
    

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72. fixed4 frag (v2f i) : SV_Target 
    

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73. { 
    

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74. // sample the texture 
    

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75. fixed4 col = tex2D(_MainTex, i.uv); 
    

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76. // apply fog 
    

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77. UNITY_APPLY_FOG(i.fogCoord, col); 
    

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78. return col; 
    

    ---

79. } 
    

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80. ENDCG 
    

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81. } 
    

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82. } 
    

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83. } 
    

    ---

显示层：

1. ---

2. ---

3. Shader "ShaderCookbook/StencilEnum" 
   

   ---

4. { 
   

   ---

5. Properties 
   

   ---

6. { 
   

   ---

7. _MainTex ("Texture", 2D) = "white" {} 
   

   ---

8. [ForceInt] 
   

   ---

9. _StencilRef("StencilRef",float) = 0 
   

   ---

10. [Enum(UnityEngine.Rendering.CompareFunction)] 
    

    ---

11. _StencilComp("StencilComp",int) =0 
    

    ---

12. [Enum(UnityEngine.Rendering.StencilOp)] 
    

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13. _StencilOp("StencilOp",int)=0 
    

    ---

14. ---

15. [ForceInt] 
    

    ---

16. _StencilReadMask("ReadMask",int)=255 
    

    ---

17. [ForceInt] 
    

    ---

18. _StencilWriteMask("WriteMask",int)=255 
    

    ---

19. } 
    

    ---

20. SubShader 
    

    ---

21. { 
    

    ---

22. Tags { "RenderType"="opaque" } 
    

    ---

23. LOD 100 
    

    ---

24. ---

25. ---

26. Pass 
    

    ---

27. { 
    

    ---

28. ---

29. Stencil{ 
    

    ---

30. Ref [_StencilRef] 
    

    ---

31. Comp[_StencilComp] 
    

    ---

32. Pass[_StencilOp] 
    

    ---

33. ReadMask[_StencilReadMask] 
    

    ---

34. WriteMask[_StencilWriteMask] 
    

    ---

35. } 
    

    ---

36. ---

37. CGPROGRAM 
    

    ---

38. #pragma vertex vert 
    

    ---

39. #pragma fragment frag 
    

    ---

40. // make fog work 
    

    ---

41. #pragma multi_compile_fog 
    

    ---

42. #include "UnityCG.cginc" 
    

    ---

43. ---

44. ---

45. struct appdata 
    

    ---

46. { 
    

    ---

47. float4 vertex : POSITION; 
    

    ---

48. float2 uv : TEXCOORD0; 
    

    ---

49. }; 
    

    ---

50. ---

51. struct v2f 
    

    ---

52. { 
    

    ---

53. float2 uv : TEXCOORD0; 
    

    ---

54. UNITY_FOG_COORDS(1) 
    

    ---

55. float4 vertex : SV_POSITION; 
    

    ---

56. }; 
    

    ---

57. ---

58. sampler2D _MainTex; 
    

    ---

59. float4 _MainTex_ST; 
    

    ---

60. v2f vert (appdata v) 
    

    ---

61. { 
    

    ---

62. v2f o; 
    

    ---

63. o.vertex = UnityObjectToClipPos(v.vertex); 
    

    ---

64. o.uv = TRANSFORM_TEX(v.uv, _MainTex); 
    

    ---

65. UNITY_TRANSFER_FOG(o,o.vertex); 
    

    ---

66. return o; 
    

    ---

67. } 
    

    ---

68. fixed4 frag (v2f i) : SV_Target 
    

    ---

69. { 
    

    ---

70. // sample the texture 
    

    ---

71. fixed4 col = tex2D(_MainTex, i.uv); 
    

    ---

72. // apply fog 
    

    ---

73. UNITY_APPLY_FOG(i.fogCoord, col); 
    

    ---

74. return col; 
    

    ---

75. } 
    

    ---

76. ENDCG 
    

    ---

77. } 
    

    ---

78. } 
    

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79. } 
    

    ---

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