﻿Shader "Hidden/PartialBlit"
{
    SubShader
    {
        Cull Front ZWrite Off ZTest Always

        Pass
        {
			Blend One OneMinusSrcAlpha

            Stencil 
            {
                Ref [_Ref]
                Comp [_Comparison]
                Pass Replace
            }

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_instancing
			#pragma fragmentoption ARB_precision_hint_fastest
            
            #include "UnityCG.cginc"
            #include "MiskCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                half3 normal : NORMAL;
				DefineTransform

                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f
            {
                float4 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;

                UNITY_VERTEX_OUTPUT_STEREO
            };
            
            half _EffectSize;

            UNITY_DECLARE_SCREENSPACE_TEXTURE(_MainTex);
            half4 _MainTex_ST;
            half4 _MainTex_TexelSize;

            UNITY_DECLARE_SCREENSPACE_TEXTURE(_InitialTex);
            half4 _InitialTex_ST;
            half4 _InitialTex_TexelSize;

			DefineCoords

            v2f vert (appdata v)
            {
                v2f o;

                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_OUTPUT(v2f, o);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
				
                o.vertex = UnityObjectToClipPos(v.vertex);

				PostprocessCoords

                ComputeScreenShift
					
				CheckY

                o.uv = ComputeScreenPos(o.vertex);
				
#if UNITY_UV_STARTS_AT_TOP
				ModifyUV
#endif
                return o;
            }
            
            half4 frag (v2f i) : SV_Target
            {
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);

                return FetchTexel(i.uv.xy/i.uv.w);
            }
            ENDCG
        }
    }
}
