Shader "Projector/Multiply" {
    Properties {
        _ShadowTex ("Cookie", 2D) = "gray" {}
        _FalloffTex ("FallOff", 2D) = "white" {}
    }
    Subshader {
        Tags {"Queue"="Transparent"}
        Pass {
            ZWrite Off
            ColorMask RGB
            Blend DstColor Zero
            Offset -1, -1

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_fog
            #include "UnityCG.cginc"
            
            struct v2f {
                float4 uvShadow : TEXCOORD0;
                float4 uvFalloff : TEXCOORD1;
                UNITY_FOG_COORDS(2)
                float4 pos : SV_POSITION;
            };
            
            float4x4 _Projector;
            float4x4 _ProjectorClip;
            
            v2f vert (float4 vertex : POSITION)
            {
                v2f o;
                o.pos = mul (UNITY_MATRIX_MVP, vertex);
                o.uvShadow = mul (_Projector, vertex);
                o.uvFalloff = mul (_ProjectorClip, vertex);
                UNITY_TRANSFER_FOG(o,o.pos);
                return o;
            }
            
            sampler2D _ShadowTex;
            sampler2D _FalloffTex;
            
            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 texS = tex2Dproj (_ShadowTex, UNITY_PROJ_COORD(i.uvShadow));
                texS.a = 1.0-texS.a;

                fixed4 texF = tex2Dproj (_FalloffTex, UNITY_PROJ_COORD(i.uvFalloff));
                fixed4 res = lerp(fixed4(1,1,1,0), texS, texF.a);

                UNITY_APPLY_FOG_COLOR(i.fogCoord, res, fixed4(1,1,1,1));
                return res;
            }
            ENDCG
        }
    }
}