Background UI Image

Hello. how can I put a image under 3D objects (on the principle of skybox)?

I used this shader

Spoiler: Shader

Shader "UI/Back3D_Default"
{
Properties
{
//[PerRendererData]
_MainTex ("Sprite 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 {

Tags {
"Queue"="Background"
"IgnoreProjector"="True"
"RenderType"="Background"

"CanUseSpriteAtlas"="True"
}


Cull Off
Lighting Off

ZWrite Off
ZTest [Always] //Less | Greater | LEqual | GEqual | Equal | NotEqual | Always

Fog { Mode Off }
Blend SrcAlpha OneMinusSrcAlpha
ColorMask [_ColorMask]

Pass {
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"

struct appdata_t {
float4 vertex : POSITION;
float4 color : COLOR;
float2 texcoord : TEXCOORD0;
};

struct v2f {
float4 vertex : SV_POSITION;
fixed4 color : COLOR;
half2 texcoord : TEXCOORD0;
};

fixed4 _Color;

v2f vert(appdata_t IN) {
v2f OUT;
OUT.vertex = mul(UNITY_MATRIX_MVP, IN.vertex);
OUT.texcoord = IN.texcoord;
OUT.color = IN.color * _Color;
return OUT;
}

sampler2D _MainTex;

fixed4 frag(v2f IN) : SV_Target {
half4 color = tex2D(_MainTex, IN.texcoord) * IN.color;
clip (color.a - 0.01);
//color.r=1;
return color;
}
ENDCG
}
}
}

But it does not work..



Help me please..

 

Simple, have a Screenspace Camera canvas with a Plane distance set to draw behind the 3D objects
Or a world space canvas placed behind or attached to the 3D hobject you want to show it behind.