Shader "Unlit/InvertTest"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
		_Delta ("Line Thickness", Range(0.0005, 0.0025)) = 0.001
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            Name "Test Filter"
            HLSLPROGRAM
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/SurfaceInput.hlsl"
            #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
            
            
            TEXTURE2D(_CameraDepthTexture);
            SAMPLER(sampler_CameraDepthTexture);
            
            float _Delta;
            int _PosterizationCount;
                        
            float SampleDepth(float2 uv)
            {
#if defined(UNITY_STEREO_INSTANCING_ENABLED) || defined(UNITY_STEREO_MULTIVIEW_ENABLED)
                return SAMPLE_TEXTURE2D_ARRAY(_CameraDepthTexture, sampler_CameraDepthTexture, uv, unity_StereoEyeIndex).r;
#else
                return SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture, uv);
#endif
            }
            
            float sobel (float2 uv) 
            {
                float2 delta = float2(_Delta, _Delta);
                
                float hr = 0;
                float vt = 0;
                
                hr += SampleDepth(uv + float2(-1.0, -1.0) * delta) *  1.0;
                hr += SampleDepth(uv + float2( 1.0, -1.0) * delta) * -1.0;
                hr += SampleDepth(uv + float2(-1.0,  0.0) * delta) *  2.0;
                hr += SampleDepth(uv + float2( 1.0,  0.0) * delta) * -2.0;
                hr += SampleDepth(uv + float2(-1.0,  1.0) * delta) *  1.0;
                hr += SampleDepth(uv + float2( 1.0,  1.0) * delta) * -1.0;
                
                vt += SampleDepth(uv + float2(-1.0, -1.0) * delta) *  1.0;
                vt += SampleDepth(uv + float2( 0.0, -1.0) * delta) *  2.0;
                vt += SampleDepth(uv + float2( 1.0, -1.0) * delta) *  1.0;
                vt += SampleDepth(uv + float2(-1.0,  1.0) * delta) * -1.0;
                vt += SampleDepth(uv + float2( 0.0,  1.0) * delta) * -2.0;
                vt += SampleDepth(uv + float2( 1.0,  1.0) * delta) * -1.0;
                
                return sqrt(hr * hr + vt * vt);
            }


            #pragma vertex vert
            #pragma fragment frag

            struct Attributes
            {
                float4 positionOS       : POSITION;
                float2 uv               : TEXCOORD0;
            };

            struct Varyings
            {
                float2 uv        : TEXCOORD0;
                float4 vertex : SV_POSITION;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            Varyings vert(Attributes input)
            {
                Varyings output = (Varyings)0;
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);

                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.vertex = vertexInput.positionCS;
                output.uv = input.uv;
                
                return output;
            }

            float4 frag (Varyings i) : SV_Target
            {
                // sample the texture
                float4 col = tex2D(_MainTex, i.uv);
                float lum = dot(col.xyz, float3(0.28, 0.58, 0.14));
                //col.xyz = (1.0 - lum.xxx)*0.5; 
                col.xyz = (1.0 - saturate(col)).xyz * 0.5;

                float s = saturate(sobel(i.uv));
                return half4(s.xxx, 1);
                //col.x = 0;

            return col;
            }
            ENDHLSL

        }
    }
}