Shader "Outline/Compose"
{
    Properties
    {
        _MainTex ("Texture", any) = "white" {}
        _EdgeTex ("Edge Texture", 2D) = "white" {}
    }
    SubShader
    {
        Cull Off ZWrite Off ZTest Always

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

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float2 uv0 : TEXCOORD0;
                float2 uv1 : TEXCOORD1;
                UNITY_VERTEX_INPUT_INSTANCE_ID 
                UNITY_VERTEX_OUTPUT_STEREO
            };

            float2 _MainTex_TexelSize;

            UNITY_DECLARE_SCREENSPACE_TEXTURE(_MainTex);
            UNITY_DECLARE_SCREENSPACE_TEXTURE(_DefaultDrawObjects);
            UNITY_DECLARE_SCREENSPACE_TEXTURE(_BlurTex);
            UNITY_DECLARE_SCREENSPACE_TEXTURE(_TempTex);
            UNITY_DECLARE_SCREENSPACE_TEXTURE(_EdgeTex);

            uniform float EdgeValue;
            
            uniform float OffsetRedX;
            uniform float OffsetGreenX;
            uniform float OffsetBlueX;
            uniform float OffsetRedY;
            uniform float OffsetGreenY;
            uniform float OffsetBlueY;

            uniform float Brightness;
            uniform float Contrast;

            uniform float GlobalAlpha;

            half4 _MainTex_ST;
            half4 _EdgeTex_ST;

            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);
                o.uv0 = TRANSFORM_TEX(v.uv, _MainTex);
                o.uv1 = TRANSFORM_TEX(v.uv, _MainTex);

                #if UNITY_UV_STARTS_AT_TOP
                if (_MainTex_TexelSize.y < 0)
                    o.uv1.y = 1 - o.uv1.y;
                #endif

                return o;
            }
            
            fixed4 frag (v2f i) : SV_Target
            {                
                EdgeValue = 1.0f;
                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);
                //
                // Sample the world RT (render so far without our outline objects)
                //
                fixed4 world = UNITY_SAMPLE_SCREENSPACE_TEXTURE(_MainTex,
                UnityStereoScreenSpaceUVAdjust(i.uv0, _MainTex_ST));
                //
                // Sample our outline texture
                //
                fixed4 outline = UNITY_SAMPLE_SCREENSPACE_TEXTURE(_BlurTex,
                UnityStereoScreenSpaceUVAdjust(i.uv1, _MainTex_ST));
                //
                // Sample the solid render of the game object to be outlined
                //
                fixed4 gameObject = UNITY_SAMPLE_SCREENSPACE_TEXTURE(_DefaultDrawObjects,
                UnityStereoScreenSpaceUVAdjust(i.uv1, _MainTex_ST));
                
                world.xyz = world + EdgeValue * (outline * (1.0 - gameObject.a));
                return world;
            }
            ENDCG
        }
    }
}