Project-M/Assets/_Project/Shaders/PixelOutline.shader

Shader "Hidden/ProjectM/PixelOutline"
{
    Properties
    {
        _PixelHeight       ("Pixel Grid Height", Float) = 200
        [ToggleUI] _PosterizeEnabled ("Posterize (banded color)", Float) = 1
        _ColorLevels       ("Posterize Levels / channel", Range(2,64)) = 12
        _Brightness        ("Brightness", Range(0.5,2)) = 1.1
        _Contrast          ("Contrast", Range(0.5,2)) = 1.05
        _Saturation        ("Saturation", Range(0,2)) = 1.35
        _DepthThreshold    ("Depth Threshold (relative)", Range(0,1)) = 0.08
        _NormalThreshold   ("Normal Threshold", Range(0,4)) = 1.0
        _OutlineThickness  ("Outline Thickness (texels)", Range(0.25,4)) = 1
        _EdgeStrength      ("Edge Strength", Range(0,1)) = 1
        [HDR] _OutlineColorOuter ("Outline Color - Depth/Silhouette", Color) = (0,0,0,1)
        [HDR] _OutlineColorInner ("Outline Color - Normal/Detail", Color) = (0,0,0,1)
        [ToggleUI] _PixelateEnabled    ("Pixelate", Float) = 1
        [ToggleUI] _DepthEdgesEnabled  ("Depth Edges", Float) = 1
        [ToggleUI] _NormalEdgesEnabled ("Normal Edges", Float) = 1
    }

    SubShader
    {
        Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" }
        ZWrite Off ZTest Always Cull Off

        Pass
        {
            Name "PixelOutline"

            HLSLPROGRAM
            #pragma vertex Vert
            #pragma fragment Frag
            #pragma target 3.5

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DeclareDepthTexture.hlsl"
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DeclareNormalsTexture.hlsl"
            #include "Packages/com.unity.render-pipelines.core/Runtime/Utilities/Blit.hlsl"

            CBUFFER_START(UnityPerMaterial)
                float  _PixelHeight;
                float  _PosterizeEnabled;
                float  _ColorLevels;
                float  _Brightness;
                float  _Contrast;
                float  _Saturation;
                float  _DepthThreshold;
                float  _NormalThreshold;
                float  _OutlineThickness;
                float  _EdgeStrength;
                float4 _OutlineColorOuter;
                float4 _OutlineColorInner;
                float  _PixelateEnabled;
                float  _DepthEdgesEnabled;
                float  _NormalEdgesEnabled;
            CBUFFER_END

            float2 SnapUV(float2 uv, float2 res)
            {
                return (floor(uv * res) + 0.5) / res;
            }

            half4 Frag(Varyings input) : SV_Target
            {
                float2 uv = input.texcoord;

                // Fixed, square-pixel low-res grid derived from a target grid height.
                float aspect = _ScreenParams.x / max(_ScreenParams.y, 1.0);
                float2 res = float2(max(_PixelHeight * aspect, 1.0), max(_PixelHeight, 1.0));

                bool doPixelate = _PixelateEnabled > 0.5;
                float2 sampleUV = doPixelate ? SnapUV(uv, res) : uv;
                float2 texel = 1.0 / res;
                float2 off = texel * _OutlineThickness;

                // Chunky fill: point-sampled scene color at the snapped grid cell.
                float3 col = SAMPLE_TEXTURE2D_X(_BlitTexture, sampler_PointClamp, sampleUV).rgb;
                col = max(col, 0.0);

                // ---- Tone shaping so flat pixel blocks read clearly ----
                col *= _Brightness;
                col = (col - 0.5) * _Contrast + 0.5;
                float luma = dot(col, float3(0.2126, 0.7152, 0.0722));
                col = lerp(luma.xxx, col, _Saturation);
                col = saturate(col);

                // ---- Posterize in perceptual (gamma) space so dark detail survives ----
                if (_PosterizeEnabled > 0.5)
                {
                    float levels = max(_ColorLevels, 2.0);
                    float3 g = pow(col, 1.0 / 2.2);
                    g = floor(g * levels + 0.5) / levels;
                    col = pow(saturate(g), 2.2);
                }

                // ---- Depth edges (outer silhouettes) ----
                float d0 = LinearEyeDepth(SampleSceneDepth(sampleUV), _ZBufferParams);
                float dL = LinearEyeDepth(SampleSceneDepth(sampleUV - float2(off.x, 0)), _ZBufferParams);
                float dR = LinearEyeDepth(SampleSceneDepth(sampleUV + float2(off.x, 0)), _ZBufferParams);
                float dD = LinearEyeDepth(SampleSceneDepth(sampleUV - float2(0, off.y)), _ZBufferParams);
                float dU = LinearEyeDepth(SampleSceneDepth(sampleUV + float2(0, off.y)), _ZBufferParams);
                float depthDiff = abs(d0 - dL) + abs(d0 - dR) + abs(d0 - dU) + abs(d0 - dD);
                float depthEdge = step(_DepthThreshold, depthDiff / max(d0, 1e-3)) * _DepthEdgesEnabled;

                // ---- Normal edges (inner detail creases) ----
                float3 n0 = SampleSceneNormals(sampleUV);
                float3 nL = SampleSceneNormals(sampleUV - float2(off.x, 0));
                float3 nR = SampleSceneNormals(sampleUV + float2(off.x, 0));
                float3 nD = SampleSceneNormals(sampleUV - float2(0, off.y));
                float3 nU = SampleSceneNormals(sampleUV + float2(0, off.y));
                float ne = (1.0 - saturate(dot(n0, nL))) + (1.0 - saturate(dot(n0, nR)))
                         + (1.0 - saturate(dot(n0, nU))) + (1.0 - saturate(dot(n0, nD)));
                float normalEdge = step(_NormalThreshold, ne) * _NormalEdgesEnabled;

                // Mask inner lines out of silhouette edges to avoid double outlines.
                float normalEdgeMasked = normalEdge * (1.0 - depthEdge);

                float edge = saturate(depthEdge + normalEdgeMasked) * _EdgeStrength;
                float3 lineCol = lerp(_OutlineColorInner.rgb, _OutlineColorOuter.rgb, depthEdge);
                float3 outCol = lerp(col, lineCol, edge);

                return half4(outCol, 1.0);
            }
            ENDHLSL
        }
    }

    Fallback Off
}