Unity shader for rendering shadows onto a transparent surface. Useful for augmented reality.

ShadowShader.shader

Shader "ShadowShader" {
	Properties{ 
		_Color("Main Color", Color) = (1,1,1,1) 
		_MainTex("Base (RGB)", 2D) = "white" {}	
		_Cutoff("Cutout", Range(0,1)) = 1.0
	}
	SubShader{
		Pass{
			Alphatest Greater[_Cutoff] SetTexture[_MainTex] 
		}
		Pass{ 
			Blend DstColor Zero Tags{ 
				"LightMode" = "ForwardBase" 
			}
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "UnityCG.cginc"
			#pragma multi_compile_fwdbase
			#include "AutoLight.cginc"
			struct v2f {
				float4 pos : SV_POSITION; LIGHTING_COORDS(0,1) 
			};
			v2f vert(appdata_base v) {
				v2f o; 
				o.pos = UnityObjectToClipPos(v.vertex); 
				TRANSFER_VERTEX_TO_FRAGMENT(o);
				return o; 
			}
			fixed4 frag(v2f i) : COLOR {
				float attenuation = LIGHT_ATTENUATION(i);
				return attenuation;
			}
			ENDCG
		} 
	} 
	Fallback "Transparent/Cutout/VertexLit" 
}