添加
1. Shader "Custom/Opaque"
2. {
3. Properties
4. {
5. [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
6. _Color ("Tint", Color) = (1,1,1,1)
8. // required for UI.Mask
9. _StencilComp ("Stencil Comparison", Float) = 8
10. _Stencil ("Stencil ID", Float) = 0
11. _StencilOp ("Stencil Operation", Float) = 0
12. _StencilWriteMask ("Stencil Write Mask", Float) = 255
13. _StencilReadMask ("Stencil Read Mask", Float) = 255
14. _ColorMask ("Color Mask", Float) = 15
15. }
16. SubShader
17. {
18. Tags
19. {
20. // ...
21. }
23. // required for UI.Mask
24. Stencil
25. {
26. Ref [_Stencil]
27. Comp [_StencilComp]
28. Pass [_StencilOp]
29. ReadMask [_StencilReadMask]
30. WriteMask [_StencilWriteMask]
31. }
32. ColorMask [_ColorMask]
34. Pass
35. {
36. // ...
37. }
38. }
39. }

原文地址 

http://answers.unity3d.com/questions/980924/ui-mask-with-shader.html