由于AR默认去掉阴影，所以要写一个shader

Shader "FX/Matte Shadow" {

Properties {
_Color ("Main Color", Color) = (1,1,1,1)
_MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
_Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
}

SubShader {

Tags {"Queue"="AlphaTest" "IgnoreProjector"="True" "RenderType"="TransparentCutout"}
LOD 200
Blend Zero SrcColor

CGPROGRAM

pragma surface surf ShadowOnly alphatest:_Cutoff

fixed4 _Color;

struct Input {
float2 uv_MainTex;
};

inline fixed4 LightingShadowOnly (SurfaceOutput s, fixed3 lightDir, fixed atten)
{
fixed4 c;
c.rgb = s.Albedo*atten;
c.a = s.Alpha;

return c;

}

void surf (Input IN, inout SurfaceOutput o)
{

fixed4 c = _Color; 
o.Albedo = c.rgb;
o.Alpha = 1;

}

ENDCG

}

Fallback "Transparent/Cutout/VertexLit"

}