该方案参考了CSDN
创建一个Shader，代码如下：
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
//需要赋给场景，专门用于解决UI置顶问题
Shader "UI/Overlay"
{
Properties
{
[PerRendererData] _MainTex ("Font Texture", 2D) = "white" {}
_Color("Tint", Color) = (1,1,1,1)
_StencilComp ("Stencil Comparison", Float) = 8
_Stencil ("Stencil ID", Float) = 0
_StencilOp ("Stencil Operation", Float) = 0
_StencilWriteMask ("Stencil Write Mask", Float) = 255
_StencilReadMask ("Stencil Read Mask", Float) = 255
_ColorMask ("Color Mask", Float) = 15
}
SubShader
{
LOD 100
Tags
{
"Queue" = "Transparent"
"IgnoreProjector" = "True"
"RenderType" = "Transparent"
"PreviewType"="Plane"
"CanUseSpriteAtlas" = "True"
}
Stencil
{
Ref [_Stencil]
Comp [_StencilComp]
Pass [_StencilOp]
ReadMask [_StencilReadMask]
WriteMask [_StencilWriteMask]
}
Cull Off
Lighting Off
ZWrite Off
ZTest Always
Offset -1, -1
Blend SrcAlpha OneMinusSrcAlpha
ColorMask [_ColorMask]
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
#include "UnityUI.cginc"
struct appdata_t
{
float4 vertex : POSITION;
float2 texcoord : TEXCOORD0;
float4 color : COLOR;
};
struct v2f
{
float4 vertex : SV_POSITION;
half2 texcoord : TEXCOORD0;
fixed4 color : COLOR;
};
sampler2D _MainTex;
float4 _MainTex_ST;
fixed4 _Color;
fixed4 _TextureSampleAdd;
v2f vert (appdata_t v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
o.color = v.color * _Color;
#ifdef UNITY_HALF_TEXEL_OFFSET
o.vertex.xy += (_ScreenParams.zw-1.0)*float2(-1,1);
#endif
return o;
}
fixed4 frag (v2f i) : SV_Target
{
fixed4 col = (tex2D(_MainTex, i.texcoord) + _TextureSampleAdd) * i.color;
clip (col.a - 0.01);
return col;
}
ENDCG
}
}
}
此时Shader没有指定材质，接下来创建一个材质Matierial：
然后，将Shader直接拖拽到这个材质上，拖拽后状态如图所示：
这时这个材质就可以使用了，这里是最关键的一步。
注意：这个材质需要赋给的是所有要显示在这个Canvas下的模型，而不是Canvas里的image，如图：
到此为止，我们就已经实现了这一需求，可以进行调试了。