Jump flood based outline effect for Unity https://medium.com/@bgolus/the-quest-for-very-wide-outlines-ba82ed442cd9

HiddenJumpFloodOutline.shader

Shader "Hidden/JumpFloodOutline"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Tags { "PreviewType" = "Plane" }
        Cull Off ZWrite Off ZTest Always

        CGINCLUDE
        // just inside the precision of a R16G16_SNorm to keep encoded range 1.0 >= and > -1.0
        #define SNORM16_MAX_FLOAT_MINUS_EPSILON ((float)(32768-2) / (float)(32768-1))
        #define FLOOD_ENCODE_OFFSET float2(1.0, SNORM16_MAX_FLOAT_MINUS_EPSILON)
        #define FLOOD_ENCODE_SCALE float2(2.0, 1.0 + SNORM16_MAX_FLOAT_MINUS_EPSILON)

        #define FLOOD_NULL_POS -1.0
        #define FLOOD_NULL_POS_FLOAT2 float2(FLOOD_NULL_POS, FLOOD_NULL_POS)
        ENDCG
        
        Pass // 0
        {
            Name "INNERSTENCIL"

            Stencil {
                Ref 1
                ReadMask 1
                WriteMask 1
                Comp NotEqual
                Pass Replace
            }

            ColorMask 0
            Blend Zero One

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            #pragma target 4.5

            float4 vert (float4 vertex : POSITION) : SV_POSITION
            {
                return UnityObjectToClipPos(vertex);
            }

            // null frag
            void frag () {}
            ENDCG
        }

        Pass // 1
        {
            Name "BUFFERFILL"

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            #pragma target 4.5

            struct appdata
            {
                float4 vertex : POSITION;
            };

            float4 vert (appdata v) : SV_POSITION
            {
                float4 pos = UnityObjectToClipPos(v.vertex);

                // flip the rendering "upside down" in non OpenGL to make things easier later
                // you'll notice none of the later passes need to pass UVs
                #ifdef UNITY_UV_STARTS_AT_TOP
                pos.y = -pos.y;
                #endif

                return pos;
            }

            half frag () : SV_Target
            {
                return 1.0;
            }
            ENDCG
        }

        Pass // 2
        {
            Name "JUMPFLOODINIT"

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            #pragma target 4.5

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

            struct v2f
            {
                float4 pos : SV_POSITION;
            };

            Texture2D _MainTex;
            float4 _MainTex_TexelSize;

            v2f vert (appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            float2 frag (v2f i) : SV_Target {
                // integer pixel position
                int2 uvInt = i.pos.xy;

                // sample silhouette texture for sobel
                half3x3 values;
                UNITY_UNROLL
                for(int u=0; u<3; u++)
                {
                    UNITY_UNROLL
                    for(int v=0; v<3; v++)
                    {
                        uint2 sampleUV = clamp(uvInt + int2(u-1, v-1), int2(0,0), (int2)_MainTex_TexelSize.zw - 1);
                        values[u][v] = _MainTex.Load(int3(sampleUV, 0)).r;
                    }
                }

                // calculate output position for this pixel
                float2 outPos = i.pos.xy * abs(_MainTex_TexelSize.xy) * FLOOD_ENCODE_SCALE - FLOOD_ENCODE_OFFSET;

                // interior, return position
                if (values._m11 > 0.99)
                    return outPos;

                // exterior, return no position
                if (values._m11 < 0.01)
                    return FLOOD_NULL_POS_FLOAT2;

                // sobel to estimate edge direction
                float2 dir = -float2(
                    values[0][0] + values[0][1] * 2.0 + values[0][2] - values[2][0] - values[2][1] * 2.0 - values[2][2],
                    values[0][0] + values[1][0] * 2.0 + values[2][0] - values[0][2] - values[1][2] * 2.0 - values[2][2]
                    );

                // if dir length is small, this is either a sub pixel dot or line
                // no way to estimate sub pixel edge, so output position
                if (abs(dir.x) <= 0.005 && abs(dir.y) <= 0.005)
                    return outPos;

                // normalize direction
                dir = normalize(dir);

                // sub pixel offset
                float2 offset = dir * (1.0 - values._m11);

                // output encoded offset position
                return (i.pos.xy + offset) * abs(_MainTex_TexelSize.xy) * FLOOD_ENCODE_SCALE - FLOOD_ENCODE_OFFSET;
            }
            ENDCG
        }

        Pass // 3
        {
            Name "JUMPFLOOD"

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            #pragma target 4.5

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
            };

            Texture2D _MainTex;
            float4 _MainTex_TexelSize;
            int _StepWidth;

            v2f vert (appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            float2 frag (v2f i) : SV_Target {
                // integer pixel position
                int2 uvInt = int2(i.pos.xy);

                // initialize best distance at infinity
                float bestDist = 1.#INF;
                float2 bestCoord;

                // jump samples
                UNITY_UNROLL
                for(int u=-1; u<=1; u++)
                {
                    UNITY_UNROLL
                    for(int v=-1; v<=1; v++)
                    {
                        // calculate offset sample position
                        int2 offsetUV = uvInt + int2(u, v) * _StepWidth;

                        // .Load() acts funny when sampling outside of bounds, so don't
                        offsetUV = clamp(offsetUV, int2(0,0), (int2)_MainTex_TexelSize.zw - 1);

                        // decode position from buffer
                        float2 offsetPos = (_MainTex.Load(int3(offsetUV, 0)).rg + FLOOD_ENCODE_OFFSET) * _MainTex_TexelSize.zw / FLOOD_ENCODE_SCALE;

                        // the offset from current position
                        float2 disp = i.pos.xy - offsetPos;

                        // square distance
                        float dist = dot(disp, disp);

                        // if offset position isn't a null position or is closer than the best
                        // set as the new best and store the position
                        if (offsetPos.y != FLOOD_NULL_POS && dist < bestDist)
                        {
                            bestDist = dist;
                            bestCoord = offsetPos;
                        }
                    }
                }

                // if not valid best distance output null position, otherwise output encoded position
                return isinf(bestDist) ? FLOOD_NULL_POS_FLOAT2 : bestCoord * _MainTex_TexelSize.xy * FLOOD_ENCODE_SCALE - FLOOD_ENCODE_OFFSET;
            }
            ENDCG
        }

        Pass // 4
        {
            Name "JUMPFLOOD_SINGLEAXIS"

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            #pragma target 4.5

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
            };

            Texture2D _MainTex;
            float4 _MainTex_TexelSize;
            int2 _AxisWidth;

            v2f vert (appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            half2 frag (v2f i) : SV_Target {
                // integer pixel position
                int2 uvInt = int2(i.pos.xy);

                // initialize best distance at infinity
                float bestDist = 1.#INF;
                float2 bestCoord;

                // jump samples
                // only one loop
                UNITY_UNROLL
                for(int u=-1; u<=1; u++)
                {
                    // calculate offset sample position
                    int2 offsetUV = uvInt + _AxisWidth * u;

                    // .Load() acts funny when sampling outside of bounds, so don't
                    offsetUV = clamp(offsetUV, int2(0,0), (int2)_MainTex_TexelSize.zw - 1);

                    // decode position from buffer
                    float2 offsetPos = (_MainTex.Load(int3(offsetUV, 0)).rg + FLOOD_ENCODE_OFFSET) * _MainTex_TexelSize.zw / FLOOD_ENCODE_SCALE;

                    // the offset from current position
                    float2 disp = i.pos.xy - offsetPos;

                    // square distance
                    float dist = dot(disp, disp);

                    // if offset position isn't a null position or is closer than the best
                    // set as the new best and store the position
                    if (offsetPos.x != -1.0 && dist < bestDist)
                    {
                        bestDist = dist;
                        bestCoord = offsetPos;
                    }
                }

                // if not valid best distance output null position, otherwise output encoded position
                return isinf(bestDist) ? FLOOD_NULL_POS_FLOAT2 : bestCoord * _MainTex_TexelSize.xy * FLOOD_ENCODE_SCALE - FLOOD_ENCODE_OFFSET;
            }
            ENDCG
        }

        Pass // 5
        {
            Name "JUMPFLOODOUTLINE"

            Stencil {
                Ref 1
                ReadMask 1
                WriteMask 1
                Comp NotEqual
                Pass Zero
                Fail Zero
            }

            Blend SrcAlpha OneMinusSrcAlpha

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            #pragma target 4.5

            struct appdata
            {
                float4 vertex : POSITION;
            };

            struct v2f
            {
                float4 pos : SV_POSITION;
            };

            Texture2D _MainTex;

            half4 _OutlineColor;
            float _OutlineWidth;

            v2f vert (appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                return o;
            }

            half4 frag (v2f i) : SV_Target {
                // integer pixel position
                int2 uvInt = int2(i.pos.xy);

                // load encoded position
                float2 encodedPos = _MainTex.Load(int3(uvInt, 0)).rg;

                // early out if null position
                if (encodedPos.y == -1)
                    return half4(0,0,0,0);

                // decode closest position
                float2 nearestPos = (encodedPos + FLOOD_ENCODE_OFFSET) * abs(_ScreenParams.xy) / FLOOD_ENCODE_SCALE;

                // current pixel position
                float2 currentPos = i.pos.xy;

                // distance in pixels to closest position
                half dist = length(nearestPos - currentPos);

                // calculate outline
                // + 1.0 is because encoded nearest position is half a pixel inset
                // not + 0.5 because we want the anti-aliased edge to be aligned between pixels
                // distance is already in pixels, so this is already perfectly anti-aliased!
                half outline = saturate(_OutlineWidth - dist + 1.0);

                // apply outline to alpha
                half4 col = _OutlineColor;
                col.a *= outline;

                // profit!
                return col;
            }
            ENDCG
        }
    }
}

JumpFloodOutlineRenderer.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Experimental.Rendering;
#if UNITY_EDITOR
using UnityEditor;
#endif

[ExecuteInEditMode]
public class JumpFloodOutlineRenderer : MonoBehaviour
{
    [ColorUsageAttribute(true, true)] public Color outlineColor = Color.white;
    [Range(0.0f, 1000.0f)] public float outlinePixelWidth = 4f;

    // list of all renderer components you want to have outlined as a single silhouette
    public List<Renderer> renderers = new List<Renderer>();

    // hidden reference to ensure shader gets included with builds
    // gets auto-assigned with an OnValidate() function later
    [HideInInspector, SerializeField] private Shader outlineShader;

    // some hidden settings
    const string shaderName = "Hidden/JumpFloodOutline";
    const CameraEvent cameraEvent = CameraEvent.AfterForwardAlpha;
    const bool useSeparableAxisMethod = true;

    // shader pass indices
    const int SHADER_PASS_INTERIOR_STENCIL = 0;
    const int SHADER_PASS_SILHOUETTE_BUFFER_FILL = 1;
    const int SHADER_PASS_JFA_INIT = 2;
    const int SHADER_PASS_JFA_FLOOD = 3;
    const int SHADER_PASS_JFA_FLOOD_SINGLE_AXIS = 4;
    const int SHADER_PASS_JFA_OUTLINE = 5;

    // render texture IDs
    private int silhouetteBufferID = Shader.PropertyToID("_SilhouetteBuffer");
    private int nearestPointID = Shader.PropertyToID("_NearestPoint");
    private int nearestPointPingPongID = Shader.PropertyToID("_NearestPointPingPong");

    // shader properties
    private int outlineColorID = Shader.PropertyToID("_OutlineColor");
    private int outlineWidthID = Shader.PropertyToID("_OutlineWidth");
    private int stepWidthID = Shader.PropertyToID("_StepWidth");
    private int axisWidthID = Shader.PropertyToID("_AxisWidth");

    // private variables
    private CommandBuffer cb;
    private Material outlineMat;
    private Camera bufferCam;

    private Mesh MeshFromRenderer(Renderer r)
    {
        if (r is SkinnedMeshRenderer)
            return (r as SkinnedMeshRenderer).sharedMesh;
        else if (r is MeshRenderer)
            return r.GetComponent<MeshFilter>().sharedMesh;

        return null;
    }

    private void CreateCommandBuffer(Camera cam)
    {
        if (renderers == null || renderers.Count == 0)
            return;

        if (cb == null)
        {
            cb = new CommandBuffer();
            cb.name = "JumpFloodOutlineRenderer: " + gameObject.name;
        }
        else
        {
            cb.Clear();
        }

        if (outlineMat == null)
        {
            outlineMat = new Material(outlineShader != null ? outlineShader : Shader.Find(shaderName));
        }

        // do nothing if no outline will be visible
        if (outlineColor.a <= (1f/255f) || outlinePixelWidth <= 0f)
        {
            cb.Clear();
            return;
        }

        // support meshes with sub meshes
        // can be from having multiple materials, complex skinning rigs, or a lot of vertices
        int renderersCount = renderers.Count;
        int[] subMeshCount = new int[renderersCount];

        for (int i=0; i<renderersCount; i++)
        {
            var mesh = MeshFromRenderer(renderers[i]);
            Debug.Assert(mesh != null, "JumpFloodOutlineRenderer's renderer [" + i + "] is missing a valid mesh.", gameObject);
            if (mesh != null)
            {
                // assume staticly batched meshes only have one sub mesh
                if (renderers[i].isPartOfStaticBatch)
                    subMeshCount[i] = 1; // hack hack hack
                else
                    subMeshCount[i] = mesh.subMeshCount;
            }
        }

        // render meshes to main buffer for the interior stencil mask
        cb.SetRenderTarget(BuiltinRenderTextureType.CameraTarget);
        for (int i=0; i<renderersCount; i++)
        {
            for (int m = 0; m < subMeshCount[i]; m++)
                cb.DrawRenderer(renderers[i], outlineMat, m, SHADER_PASS_INTERIOR_STENCIL);
        }

        // match current quality settings' MSAA settings
        // doesn't check if current camera has MSAA enabled
        // also could just always do MSAA if you so pleased
        int msaa = Mathf.Max(1,QualitySettings.antiAliasing);

        int width = cam.scaledPixelWidth;
        int height = cam.scaledPixelHeight;

        // setup descriptor for silhouette render texture
        RenderTextureDescriptor silhouetteRTD = new RenderTextureDescriptor() {
            dimension = TextureDimension.Tex2D,
            graphicsFormat = GraphicsFormat.R8_UNorm,

            width = width,
            height = height,

            msaaSamples = msaa,
            depthBufferBits = 0,

            sRGB = false,

            useMipMap = false,
            autoGenerateMips = false
        };

        // create silhouette buffer and assign it as the current render target
        cb.GetTemporaryRT(silhouetteBufferID, silhouetteRTD, FilterMode.Point);
        cb.SetRenderTarget(silhouetteBufferID);
        cb.ClearRenderTarget(false, true, Color.clear);

        // render meshes to silhouette buffer
        for (int i=0; i<renderersCount; i++)
        {
            for (int m = 0; m < subMeshCount[i]; m++)
                cb.DrawRenderer(renderers[i], outlineMat, m, SHADER_PASS_SILHOUETTE_BUFFER_FILL);
        }

        // Humus3D wire trick, keep line 1 pixel wide and fade alpha instead of making line smaller
        // slightly nicer looking and no more expensive
        Color adjustedOutlineColor = outlineColor;
        adjustedOutlineColor.a *= Mathf.Clamp01(outlinePixelWidth);
        cb.SetGlobalColor(outlineColorID, adjustedOutlineColor.linear);
        cb.SetGlobalFloat(outlineWidthID, Mathf.Max(1f, outlinePixelWidth));

        // setup descriptor for jump flood render textures
        var jfaRTD = silhouetteRTD;
        jfaRTD.msaaSamples = 1;
        jfaRTD.graphicsFormat = GraphicsFormat.R16G16_SNorm;

        // create jump flood buffers to ping pong between
        cb.GetTemporaryRT(nearestPointID, jfaRTD, FilterMode.Point);
        cb.GetTemporaryRT(nearestPointPingPongID, jfaRTD, FilterMode.Point);

        // calculate the number of jump flood passes needed for the current outline width
        // + 1.0f to handle half pixel inset of the init pass and antialiasing
        int numMips = Mathf.CeilToInt(Mathf.Log(outlinePixelWidth + 1.0f, 2f));
        int jfaIter = numMips-1;

        // Alan Wolfe's separable axis JFA - https://www.shadertoy.com/view/Mdy3D3
        if (useSeparableAxisMethod)
        {

            // jfa init
            cb.Blit(silhouetteBufferID, nearestPointID, outlineMat, SHADER_PASS_JFA_INIT);

            // jfa flood passes
            for (int i=jfaIter; i>=0; i--)
            {
                // calculate appropriate jump width for each iteration
                // + 0.5 is just me being cautious to avoid any floating point math rounding errors
                float stepWidth = Mathf.Pow(2, i) + 0.5f;

                // the two separable passes, one axis at a time
                cb.SetGlobalVector(axisWidthID, new Vector2(stepWidth, 0f));
                cb.Blit(nearestPointID, nearestPointPingPongID, outlineMat, SHADER_PASS_JFA_FLOOD_SINGLE_AXIS);
                cb.SetGlobalVector(axisWidthID, new Vector2(0f, stepWidth));
                cb.Blit(nearestPointPingPongID, nearestPointID, outlineMat, SHADER_PASS_JFA_FLOOD_SINGLE_AXIS);
            }
        }

        // traditional JFA
        else
        {
            // choose a starting buffer so we always finish on the same buffer
            int startBufferID = (jfaIter % 2 == 0) ? nearestPointPingPongID : nearestPointID;

            // jfa init
            cb.Blit(silhouetteBufferID, startBufferID, outlineMat, SHADER_PASS_JFA_INIT);

            // jfa flood passes
            for (int i=jfaIter; i>=0; i--)
            {
                // calculate appropriate jump width for each iteration
                // + 0.5 is just me being cautious to avoid any floating point math rounding errors
                cb.SetGlobalFloat(stepWidthID, Mathf.Pow(2, i) + 0.5f);

                // ping pong between buffers
                if (i % 2 == 1)
                    cb.Blit(nearestPointID, nearestPointPingPongID, outlineMat, SHADER_PASS_JFA_FLOOD);
                else
                    cb.Blit(nearestPointPingPongID, nearestPointID, outlineMat, SHADER_PASS_JFA_FLOOD);
            }
        }

        // jfa decode & outline render
        cb.Blit(nearestPointID, BuiltinRenderTextureType.CameraTarget, outlineMat, SHADER_PASS_JFA_OUTLINE);

        cb.ReleaseTemporaryRT(silhouetteBufferID);
        cb.ReleaseTemporaryRT(nearestPointID);
        cb.ReleaseTemporaryRT(nearestPointPingPongID);
    }

    void ApplyCommandBuffer(Camera cam)
    {
        #if UNITY_EDITOR
        // hack to avoid rendering in the inspector preview window
        if (cam.gameObject.name == "Preview Scene Camera")
            return;
        #endif

        if (bufferCam != null)
        {
            if(bufferCam == cam)
                return;
            else
                RemoveCommandBuffer(cam);
        }

        Plane[] planes = GeometryUtility.CalculateFrustumPlanes(cam);

        // skip rendering if none of the renderers are in view
        bool visible = false;
        for (int i=0; i<renderers.Count; i++)
        {
            if (GeometryUtility.TestPlanesAABB(planes, renderers[i].bounds))
            {
                visible = true;
                break;
            }
        }

        if (!visible)
            return;

        CreateCommandBuffer(cam);
        if (cb == null)
            return;

        bufferCam = cam;
        bufferCam.AddCommandBuffer(cameraEvent, cb);
    }

    void RemoveCommandBuffer(Camera cam)
    {
        if (bufferCam != null && cb != null)
        {
            bufferCam.RemoveCommandBuffer(cameraEvent, cb);
            bufferCam = null;
        }
    }

    void OnEnable()
    {
        Camera.onPreRender += ApplyCommandBuffer;
        Camera.onPostRender += RemoveCommandBuffer;
    }

    void OnDisable()
    {
        Camera.onPreRender -= ApplyCommandBuffer;
        Camera.onPostRender -= RemoveCommandBuffer;
    }

#if UNITY_EDITOR
    void OnValidate()
    {
        if (renderers != null)
        {
            for (int i=renderers.Count-1; i>-1; i--)
            {
                if (renderers[i] == null || (!(renderers[i] is SkinnedMeshRenderer) && !(renderers[i] is MeshRenderer)))
                    renderers.RemoveAt(i);
                else
                {
                    bool foundDuplicate = false;
                    for (int k=0; k<i; k++)
                    {
                        if (renderers[i] == renderers[k])
                        {
                            foundDuplicate = true;
                            break;
                        }
                    }

                    if (foundDuplicate)
                        renderers.RemoveAt(i);
                }
            }
        }

        if (outlineShader == null)
            outlineShader = Shader.Find(shaderName);
    }

    public void FindActiveMeshes()
    {
        Undo.RecordObject(this, "Filling with all active Renderer components");
        GameObject parent = this.gameObject;
        if (renderers != null)
        {
            foreach (var renderer in renderers)
            {
                if (renderer)
                {
                    parent = renderer.transform.parent.gameObject;
                    break;
                }
            }
        }

        if (parent != null)
        {
            var skinnedMeshes = parent.GetComponentsInChildren<SkinnedMeshRenderer>(true);
            var meshes = parent.GetComponentsInChildren<MeshRenderer>(true);
            if (skinnedMeshes.Length > 0 || meshes.Length > 0)
            {
                foreach (var sk in skinnedMeshes)
                {
                    if (sk.gameObject.activeSelf)
                        renderers.Add(sk);
                }
                foreach (var mesh in meshes)
                {
                    if (mesh.gameObject.activeSelf)
                        renderers.Add(mesh);
                }
                OnValidate();
            }
            else
                Debug.LogError("No Active Meshes Found");
        }
    }
#endif
}

#if UNITY_EDITOR
[CustomEditor(typeof(JumpFloodOutlineRenderer))]
public class JumpFloodOutlineRendererEditor : Editor
{
    public override void OnInspectorGUI()
    {
        base.OnInspectorGUI();

        if (GUILayout.Button("Get Active Children Renderers"))
        {
            UnityEngine.Object[] objs = serializedObject.targetObjects;

            foreach (var obj in objs)
            {
                var mh = (obj as JumpFloodOutlineRenderer);
                mh.FindActiveMeshes();
            }
        }
    }
}
#endif

On the game my implementation of this first shipped with, I implemented it working at a lower resolution and upscaling via an intermediate distance field texture to handle lower performance systems or very high resolutions. The main things I had to make sure were to use at least an RHalf for the intermediate texture format, and make sure it really was using bilinear filtering. And yes, after that it still looked a bit chunky, but you had to look really close to catch it. It shouldn't look pixelated, but it will look a little chunky with some hard diagonals instead of nicely rounded corners. Unity does really like to force render textures to be point filtered, so double check it really isn't being sampled that way. You might even want to use an inline sampler state to absolutely force it to behave.

I had it fall back to this mode on any resolution over 1080, and run at no more than that 1080p resolution for all of the passes. And it ran in this mode at all times on the Switch, I think capping out at 640x240 (half of 720p). For the most part I don't think most people will notice. Certainly no one else working on that project found it objectionable.

Unreal has a JFA implementaiton it ships with in one of it's optional packages. In their case they assume none of the data being fed into it has anti-aliasing. So they apply a small gaussian blur to the intermediate distance field texture to fake anti-aliasing. This won't help the upscaling chunkiness alone, but a very cheap 4 sample 1.5 texel blur could be done at the full screen resolution during the final pass to help alleviate some of the chunkiness for not too much cost.

I think the problem was that the outline width I'm using is very small... I set it at 1 up to 5 and that was pixelated. Using a larger value like 50, things start to round off. We want very narrow outlines so I'm starting to think this may not be the best approach in that case. Maybe brute forcing it would be faster (?). Anyway, thanks again!

Ah, Yeah.

There's a lot of things I did for the production version of this shader to handle things like that. The above sample code limits the actual line width to 1 pixel, and then fades out the line opacity below that. When doing downsampled outlines, you need to limit it to 1 texel of the downsampled resolution.

As for being "faster", if you look at the article this example code is from, you'll see that JFA was faster for literally everything not a single pixel wide. But not by much. So if you want a single pixel, brute force. If you ever want more than one pixel, JFA.