Wide Outlines Renderer Feature for URP and ECS/DOTS/Hybrid Renderer

info.md

Wide Outlines Renderer Feature for URP and ECS/DOTS/Hybrid Renderer

Usage

1. Create a new Unity game object layer for the objects you wish to outline.
2. In your URP asset, turn on MSAA or disable the Depth Texture.
3. In the ForwardRendererData asset of your URP asset, add the renderer feature named "Outline Feature"
4. Set the Layer Mask to the layer created in step 1.
5. Add the objects you wish to outline to the outline layer (this can be done at runtime in ECS by setting the layer of the RenderMesh).
6. Adjust the color and width of the outlines as desired in the renderer feature settings.

Notes

When I first added support for the Hyrbid Renderer, render layers were not working correctly. This required the use of game object layers to filter out the outlined objects. This might be fixed now, but I have not tested it yet.

Credits

• The technique for these wide outlines comes from Ben Golus which is described and implemented in this article.
• Alexander Ameye created the renderer feature and shader modifications to make this work in URP, original shared here.
• Scott Daley modified the shader to get it working with Unity ECS and the Hybrid Renderer.

Compatibility

Test with:

• Unity 2020.3.30f1
• URP 10.8.1
• Entities 0.50.0-preview.24
• Hybrid Renderer 0.50.0-preview.24

Outline.shader

// Original shader by @bgolus, modified slightly by @alexanderameye for URP, modified slightly more
// by @gravitonpunch for ECS/DOTS/HybridRenderer.
// https://twitter.com/bgolus
// https://medium.com/@bgolus/the-quest-for-very-wide-outlines-ba82ed442cd9
// https://alexanderameye.github.io/
// https://twitter.com/alexanderameye/status/1332286868222775298

Shader "Hidden/Outline"
{
    Properties 
    { 
        [HideInInspector] _MainTex ("Texture", 2D) = "white" {}
        _OutlineColor("Color", Color) = (1, 1, 1, 1)
        _OutlineWidth ("Width", Range (0, 20)) = 5
    }

    SubShader
    {
        Tags { "RenderType"="Opaque" "RenderPipeline" = "UniversalPipeline"}

        Cull Off ZWrite Off ZTest Always

        HLSLINCLUDE
        #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)
        ENDHLSL

        Pass // 0
        {
            Name "STENCIL MASK"

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

            ColorMask 0
            Blend Zero One
            
            HLSLPROGRAM
            #pragma multi_compile_instancing
            #pragma multi_compile _ DOTS_INSTANCING_ON
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"        

            #pragma target 4.5

            struct appdata
            {
                float4 positionOS : POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : INSTANCEID_SEMANTIC;
                #endif
            };

            float4 vert (appdata i) : SV_POSITION
            {
                UNITY_SETUP_INSTANCE_ID(i);
                return TransformObjectToHClip(i.positionOS.xyz);
            }

            void frag () {}
            ENDHLSL
        }

        Pass // 1
        {
            Name "BUFFERFILL"

            HLSLPROGRAM
            #pragma multi_compile_instancing
            #pragma multi_compile _ DOTS_INSTANCING_ON
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"        

            #pragma target 4.5

            struct appdata
            {
                float4 positionOS : POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : INSTANCEID_SEMANTIC;
                #endif
            };

            float4 vert (appdata i) : SV_POSITION
            {
                UNITY_SETUP_INSTANCE_ID(i);
                float4 pos = TransformObjectToHClip(i.positionOS.xyz);

                // 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;
            }
            ENDHLSL
        }

        Pass // 2
        {
            Name "JUMPFLOODINIT"

            HLSLPROGRAM
            #pragma multi_compile_instancing
            #pragma multi_compile _ DOTS_INSTANCING_ON
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"        

            #pragma target 4.5

            struct appdata
            {
                float4 positionOS : POSITION;
                float2 uv : TEXCOORD0;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : INSTANCEID_SEMANTIC;
                #endif
            };

            struct v2f
            {
                float4 positionCS : SV_POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : CUSTOM_INSTANCE_ID;
                #endif
            };

            Texture2D _MainTex;

            CBUFFER_START(UnityPerMaterial)
            float4 _MainTex_TexelSize;
            half4 _OutlineColor;
            float _OutlineWidth;
            CBUFFER_END

            v2f  vert (appdata i)
            {
                UNITY_SETUP_INSTANCE_ID(i);
                v2f o;
                o.positionCS = TransformObjectToHClip(i.positionOS.xyz);

                return o;
            }

            float2 frag (v2f i) : SV_TARGET
            {
                // integer pixel position
                int2 uvInt = i.positionCS.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.positionCS.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.positionCS.xy + offset) * abs(_MainTex_TexelSize.xy) * FLOOD_ENCODE_SCALE - FLOOD_ENCODE_OFFSET;
            }
            ENDHLSL
        }

        Pass // 3
        {
            Name "JUMPFLOOD_SINGLEAXIS"

            HLSLPROGRAM
            #pragma multi_compile_instancing
            #pragma multi_compile _ DOTS_INSTANCING_ON
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"        

            #pragma target 4.5

            struct appdata
            {
                float4 positionOS : POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : INSTANCEID_SEMANTIC;
                #endif
            };

            struct v2f
            {
                float4 positionCS : SV_POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : CUSTOM_INSTANCE_ID;
                #endif
            };

            Texture2D _MainTex;
            CBUFFER_START(UnityPerMaterial)
            float4 _MainTex_TexelSize;
            half4 _OutlineColor;
            float _OutlineWidth;
            CBUFFER_END
            int2 _AxisWidth;

            v2f  vert (appdata i)
            {
                UNITY_SETUP_INSTANCE_ID(i);
                v2f o;
                o.positionCS = TransformObjectToHClip(i.positionOS.xyz);

                return o;
            }

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

                // initialize best distance at infinity
                float bestDist = 100000000;
                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.positionCS.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;
            }
            ENDHLSL
        }

        Pass // 4
        {
            Name "OUTLINE"

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

           Blend SrcAlpha OneMinusSrcAlpha

            HLSLPROGRAM
            #pragma multi_compile_instancing
            #pragma multi_compile _ DOTS_INSTANCING_ON
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"        

            #pragma target 4.5

            struct appdata
            {
                float4 positionOS : POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : INSTANCEID_SEMANTIC;
                #endif
            };

            struct v2f
            {
                float4 positionCS : SV_POSITION;
                #if UNITY_ANY_INSTANCING_ENABLED
                uint instanceID : CUSTOM_INSTANCE_ID;
                #endif
            };

            Texture2D _MainTex;
            
            CBUFFER_START(UnityPerMaterial)
            float4 _MainTex_TexelSize;
            half4 _OutlineColor;
            float _OutlineWidth;
            CBUFFER_END

            v2f  vert (appdata i)
            {
                UNITY_SETUP_INSTANCE_ID(i);
                v2f o;
                o.positionCS = TransformObjectToHClip(i.positionOS.xyz);

                return o;
            }

           half4 frag (v2f i) : SV_Target {
                // integer pixel position
                int2 uvInt = int2(i.positionCS.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.positionCS.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;
            }
            ENDHLSL
        }
    }
}

OutlineFeature.cs

// Modified version of outline renderer feature by Alexander Ameye.
// https://alexanderameye.github.io/
// https://twitter.com/alexanderameye/status/1332286868222775298

using System;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class OutlineFeature : ScriptableRendererFeature
{
    public Settings OutlineSettings;
    private OutlinePass _outlinePass;
    private StencilPass _stencilPass;

    [Serializable]
    public class Settings
    {
        [Header("Visual")]
        [ColorUsage(true, true)]
        public Color Color = new Color(0.2f, 0.4f, 1, 1f);

        [Range(0.0f, 20.0f)]
        public float Width = 5f;

        [Header("Rendering")]
        public LayerMask LayerMask = 0;

        // TODO: Try this again when render layers are working with hybrid renderer.
        // [Range(0, 32)]
        // public int RenderLayer = 1;

        public RenderPassEvent RenderPassEvent = RenderPassEvent.AfterRenderingTransparents;

        public SortingCriteria SortingCriteria = SortingCriteria.CommonOpaque;
    }

    public override void Create()
    {
        if (OutlineSettings == null)
        {
            return;
        }
        _stencilPass = new StencilPass(OutlineSettings);
        _outlinePass = new OutlinePass(OutlineSettings);
    }

    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        if (OutlineSettings == null)
        {
            return;
        }
        renderer.EnqueuePass(_stencilPass);
        renderer.EnqueuePass(_outlinePass);
    }
}

OutlinePass.cs

// Modified version of outline render pass by Alexander Ameye.
// https://alexanderameye.github.io/
// https://twitter.com/alexanderameye/status/1332286868222775298

using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Experimental.Rendering;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class OutlinePass : ScriptableRenderPass
{
    private const string ProfilerTag = "Outline Pass";
    private const string ShaderName = "Hidden/Outline";

    private static readonly ShaderTagId _srpDefaultUnlit = new ShaderTagId("SRPDefaultUnlit");
    private static readonly ShaderTagId _universalForward = new ShaderTagId("UniversalForward");
    private static readonly ShaderTagId _lightweightForward = new ShaderTagId("LightweightForward");

    private static readonly List<ShaderTagId> _shaderTags = new List<ShaderTagId>
    {
        _srpDefaultUnlit, _universalForward, _lightweightForward,
    };

    private static readonly int _silhouetteBufferID = Shader.PropertyToID("_SilhouetteBuffer");
    private static readonly int _nearestPointID = Shader.PropertyToID("_NearestPoint");
    private static readonly int _nearestPointPingPongID = Shader.PropertyToID("_NearestPointPingPong");
    private static readonly int _axisWidthID = Shader.PropertyToID("_AxisWidth");
    private static readonly int _outlineColorID = Shader.PropertyToID("_OutlineColor");
    private static readonly int _outlineWidthID = Shader.PropertyToID("_OutlineWidth");
    private readonly Material _bufferFillMaterial;
    private readonly Material _outlineMaterial;
    private readonly OutlineFeature.Settings _settings;
    private RenderTargetIdentifier _cameraColor;
    private FilteringSettings _filteringSettings;

    public OutlinePass(OutlineFeature.Settings settings)
    {
        profilingSampler = new ProfilingSampler(ProfilerTag);
        _settings = settings;
        renderPassEvent = settings.RenderPassEvent;

        // TODO: Try this again when render layers are working with hybrid renderer.
        // uint renderingLayerMask = 1u << settings.RenderLayer - 1;
        // _filteringSettings = new FilteringSettings(RenderQueueRange.all, settings.LayerMask.value, renderingLayerMask);
        _filteringSettings = new FilteringSettings(RenderQueueRange.all, settings.LayerMask.value);

        if (!_outlineMaterial)
        {
            _outlineMaterial = CoreUtils.CreateEngineMaterial(ShaderName);
        }
        _outlineMaterial.SetColor(_outlineColorID, settings.Color);
        _outlineMaterial.SetFloat(_outlineWidthID, Mathf.Max(1f, settings.Width));
    }

    public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
    {
        RenderTextureDescriptor descriptor = renderingData.cameraData.cameraTargetDescriptor;

        descriptor.graphicsFormat = GraphicsFormat.R8_UNorm;
        descriptor.msaaSamples = 1;
        descriptor.depthBufferBits = 0;
        descriptor.sRGB = false;
        descriptor.useMipMap = false;
        descriptor.autoGenerateMips = false;
        cmd.GetTemporaryRT(_silhouetteBufferID, descriptor, FilterMode.Point);

        descriptor.graphicsFormat = GraphicsFormat.R16G16_SNorm;
        cmd.GetTemporaryRT(_nearestPointID, descriptor, FilterMode.Point);
        cmd.GetTemporaryRT(_nearestPointPingPongID, descriptor, FilterMode.Point);

        ConfigureTarget(_silhouetteBufferID);
        ConfigureClear(ClearFlag.Color, Color.clear);

        _cameraColor = renderingData.cameraData.renderer.cameraColorTarget;
    }

    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
        DrawingSettings drawingSettings = CreateDrawingSettings(
            _shaderTags,
            ref renderingData,
            _settings.SortingCriteria
        );
        drawingSettings.overrideMaterial = _outlineMaterial;
        drawingSettings.overrideMaterialPassIndex = 1;

        int numMips = Mathf.CeilToInt(Mathf.Log(_settings.Width + 1.0f, 2f));
        int jfaIterations = numMips - 1;

        // TODO: Switch to this once mismatched markers bug is fixed.
        // CommandBuffer cmd = CommandBufferPool.Get(ProfilerTag);
        CommandBuffer cmd = CommandBufferPool.Get();
        using (new ProfilingScope(cmd, profilingSampler))
        {
            context.ExecuteCommandBuffer(cmd);
            cmd.Clear();

            context.DrawRenderers(renderingData.cullResults, ref drawingSettings, ref _filteringSettings);
            Blit(cmd, _silhouetteBufferID, _nearestPointID, _outlineMaterial, 2);

            for (int i = jfaIterations; i >= 0; i--)
            {
                float stepWidth = Mathf.Pow(2, i) + 0.5f;

                cmd.SetGlobalVector(_axisWidthID, new Vector2(stepWidth, 0f));
                Blit(cmd, _nearestPointID, _nearestPointPingPongID, _outlineMaterial, 3);
                cmd.SetGlobalVector(_axisWidthID, new Vector2(0f, stepWidth));
                Blit(cmd, _nearestPointPingPongID, _nearestPointID, _outlineMaterial, 3);
            }

            cmd.Blit(_nearestPointID, _cameraColor, _outlineMaterial, 4);
        }

        context.ExecuteCommandBuffer(cmd);
        CommandBufferPool.Release(cmd);
    }

    public override void OnCameraCleanup(CommandBuffer cmd)
    {
        if (cmd == null)
        {
            throw new ArgumentNullException("cmd");
        }

        cmd.ReleaseTemporaryRT(_silhouetteBufferID);
        cmd.ReleaseTemporaryRT(_nearestPointID);
        cmd.ReleaseTemporaryRT(_nearestPointPingPongID);
    }
}

StencilPass.cs

// Modified version of stencil render pass by Alexander Ameye.
// https://alexanderameye.github.io/
// https://twitter.com/alexanderameye/status/1332286868222775298

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class StencilPass : ScriptableRenderPass
{
    private const string ProfilerTag = "Stencil Pass";
    private const string ShaderName = "Hidden/Outline";

    private static readonly ShaderTagId _srpDefaultUnlit = new ShaderTagId("SRPDefaultUnlit");
    private static readonly ShaderTagId _universalForward = new ShaderTagId("UniversalForward");
    private static readonly ShaderTagId _lightweightForward = new ShaderTagId("LightweightForward");

    private static readonly List<ShaderTagId> _shaderTags = new List<ShaderTagId>
    {
        _srpDefaultUnlit, _universalForward, _lightweightForward,
    };

    private readonly OutlineFeature.Settings _settings;

    private readonly Material _stencilMaterial;
    private FilteringSettings _filteringSettings;

    public StencilPass(OutlineFeature.Settings settings)
    {
        profilingSampler = new ProfilingSampler(ProfilerTag);
        _settings = settings;
        renderPassEvent = settings.RenderPassEvent;

        // TODO: Try this again when render layers are working with hybrid renderer.
        // uint renderingLayerMask = 1u << settings.RenderLayer - 1;
        // _filteringSettings = new FilteringSettings(RenderQueueRange.all, settings.LayerMask.value, renderingLayerMask);
        _filteringSettings = new FilteringSettings(RenderQueueRange.all, settings.LayerMask.value);

        if (!_stencilMaterial)
        {
            _stencilMaterial = CoreUtils.CreateEngineMaterial(ShaderName);
        }
    }

    public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
    {
        DrawingSettings drawingSettings = CreateDrawingSettings(
            _shaderTags,
            ref renderingData,
            _settings.SortingCriteria
        );
        drawingSettings.overrideMaterial = _stencilMaterial;
        drawingSettings.overrideMaterialPassIndex = 0;

        // TODO: Switch to this once mismatched markers bug is fixed.
        // CommandBuffer cmd = CommandBufferPool.Get(ProfilerTag);
        CommandBuffer cmd = CommandBufferPool.Get();
        using (new ProfilingScope(cmd, profilingSampler))
        {
            context.ExecuteCommandBuffer(cmd);
            cmd.Clear();
            context.DrawRenderers(renderingData.cullResults, ref drawingSettings, ref _filteringSettings);
        }

        context.ExecuteCommandBuffer(cmd);
        CommandBufferPool.Release(cmd);
    }
}

Hey @jwindie, this is an issue that a few people have mentioned. I don't fully understand the problem, but it has something to do with the stencil getting cleared with certain configurations. There are a few different settings you can try. Firstly, if you don't need it, you can disable Depth Texture in the renderer settings. Alternatively, you can try enabling MSAA in the renderer settings. Finally, you can mess with the Render Pass Event in the outline settings. You might need to try a combination of these.

I've actually reworked how the outline stencils are being done in my own project that avoids this issue. If I have some time, I'll try to update this post with those changes.

In case anyone is having trouble with these outlines in a build, you need to make sure the outline shader is being loaded. There are two ways that I know how to do this.

A) Add the "Outline" shader to the list of "Always Included Shaders" under Project Settings > Graphics > Build-in Shader Settings:

B) Create a Shader Variant Collection and include the "Outline" shader inside of it:

Hi. Could you share how you fix that issue? It would be really great.

Hi. Could you share how you fix that issue? It would be really great.

I'm not currently using this shader in my own project so its hard to test again, but based on my last reply, you could try messing with the depth texture and MSAA settings:

If I recall correctly, enabling MSAA or disabling the Depth Texture fixed the issue. Alternatively, you could try using a different render pass event in the outline settings.

I believe the issue is that the stencil values are getting cleared between the two render passes. In the first pass, the objects that are going to be outlined are rendered. Each rendered pixel writes a value to the stencil buffer. Then the second pass renders the objects again and generates the outline silhouette. At the end of the second pass, it cuts out all the pixels that had a stencil value set in the first pass. If the stencil buffer is cleared, it will fail to do so like in those screenshots.

The generation of the Depth Texture and MSAA both rely on the depth texture which is coupled with the stencil buffer. That's why toggling those settings can sometimes fix the issue.

It is possible to rewrite the shader in a way that does all of this in a single RenderPass (technically still multiple gpu passes, but guaranteed to run right after each other when packaged up in a single RenderPass). This ensures that the stencil values won't be cleared by something out of your control. Unfortunately, I haven't had time to update this shader to do this. It is also surprisingly difficult to make this work due to how the unity render pipelines handle the camera depth texture. Many things just don't work how they should.

I figured it out.

1. Remove descriptor.depthBufferBits = 0;
2. Set ConfigureClear(ClearFlag.All, Color.clear);
3. Then render mask to maskBuffer and set cmd.SetGlobalTexture(_maskTextureID, _maskBufferID);
4. Change Outline shader to clip it for example:

half4 color = _MainMaskTex.Sample(sampler_MainMaskTex, i.uv);
if (color.r > 0.5) {
    return half4(0,0,0,0);
}

@makamekm сould you share your solution?

It is possible to rewrite the shader in a way that does all of this in a single RenderPass (technically still multiple gpu passes, but guaranteed to run right after each other when packaged up in a single RenderPass).

Would that be useful for performance as well?

It is possible to rewrite the shader in a way that does all of this in a single RenderPass (technically still multiple gpu passes, but guaranteed to run right after each other when packaged up in a single RenderPass).

Would that be useful for performance as well?

Not necessarily. The GPU would still be doing the same exact draw calls, but they would be set up and organized slightly differently. The terminology used by unity's render pipelines makes this quite confusing to talk about. A ScriptableRenderPass is not one-to-one with an draw call on the GPU. A fullscreen draw call is sometimes referred to as a render pass, but that is not the same thing as a ScriptableRenderPass. A single ScriptableRenderPass can execute many draw calls, and often does.

When I said you could do this all in a single ScriptableRenderPass, I just mean executing both the stencil and outline draw calls from the same place.

Technically, there might be some subtle differences in the CPU performance by reducing the number of ScriptableRenderPass in your render pipeline, but I think it would have negligible impact.

With that said, I'm not a graphics performance expert, so I might be totally wrong about all of this.

If I recall correctly, enabling MSAA or disabling the Depth Texture fixed the issue.

You recalled correctly, when I disabled the Depth Texture in my Universal Render Pipeline Asset the outline started to work correctly.

I can confirm also that the outline is working like a charm in Unity 2021.3.16f with URP 12.1.8 in builds of PC (Windows and Mac), Android and Iphone.

Really thanks @ScottJDaley for sharing your work, I'm learning a lot. I'll stay tuned in case you upgrade/improve your project. I'll give you my best feedback.

@makamekm / @ScottJDaley -- curious to hear from you since I can't quite figure out what I'm doing wrong.
Using URP version 14.0.6
Unity Version 2022.2.10

Here is the image of 2 enemies (1 as a cube for testing, another as a Skeleton with animations etc)

Renderer Feature settings:

Added to Always Include shader list:

URP Settings with Depth Texture enabled and MSAA set to 8x:

Here you can see I try enabling the Renderer Feature but the entire object is being covered up (first screenshot shows a semi-transparent color -- 2nd screenshot shows a 1.0 alpha color):

Semi-Transparent alpha on Color	Full Alpha on Color

Interestingly, if i change the Render Pass Event to be After Transparents, the Canvas slider / image gets obfuscated too:

But no matter which setting i enable / disable, it doesn't seem to affect the Overlaying of the color over the entire object:

Depth On, 8x MSAA	Depth Off, 8x MSAA

Depth On, MSAA Disabled	Depth Off, MSAA Disabled

And lastly, even in Game mode (not just Scene view), the outline shader / feature seems to be overlaying color over the entire object:

Also fwiw, i'm getting a decent amount of "deprecated" warnings in the OutlinePass.cs script:

@keitzer I think because it's still using the old render feature API, not the new RTHandle API.

@ArieLeo

possibly -- but even with the deprecated warnings i was able to figure out a workaround / possible solution to this

i have a Renderer Feature for each Player that would have their own highlight -- followed by a Renderer Feature which renders the same object as Opaque.

It even works with the object being obstructed which is nice:

Basically using this as a targeting system to show which "enemy" or object you're aiming at (or in the case of multiple players aiming at the same target -- very similar to what Minecraft Dungeons does)

There's still the issue of overlapping draw calls on these objects which actually removes the "outline" since all outlines happen behind these objects -- otherwise i think it looks great and is easy to change the Layer of the objects and the highlight simply applies with basically no change in Framerate

유니티 URP 2021.3.19f1 에서
외곽선이 오브젝트를 뒤덮는 현상을 해결했습니다.

저의 경우, Renderer Asset에서 Depth Priming Mode를 Disabled로 변경하니 올바르게 동작했습니다.

unfortunately, doesn't work. Is @keitzer's solution the recommended one? I get the same results, silhouette won't render below the model. I think I'll try and write an updated one when I have more time for a deep dive.

unfortunately, doesn't work. Is @keitzer's solution the recommended one? I get the same results, silhouette won't render below the model. I think I'll try and write an updated one when I have more time for a deep dive.

Render Type이 Overlay인 카메라를 추가한 이후로, 저도 다시 동일한 문제가 발생했습니다.

Yeah if there's a better way that might increase FPS i'm all for it

But as of right now i got pretty high FPS on a macbook air using this method so i'm okay with it for now.

Okay so I think i figured it out, for anyone following in my footsteps of trying to make a Renderer Feature read stencil and it bugging out:
So, sometimes, renderingData.cameraData.renderer.cameraColorTarget has both the depth (depthStencilFormat = D32_SFloat_S8_UInt) and color (graphicsFormat = B10G11R11_UFloatPack32) in one. Presumably cameraDepthTarget is unused.

But then sometimes URP goes and splits them into two textures, cameraColorTarget has color but (depthStencilFormat = None), and renderingData.cameraData.renderer.cameraDepthTarget has (depthStencilFormat = D32_SFloat_S8_UInt)

example of this split mode being active

And here's the kicker: When this split is active (and god knows what can activate it, look into urp source code), calling CommandBuffer.SetRenderTarget(destination) / ConfigureTarget() / Blit() with the overload of only one RenderTargetIdentifier will leave the depth texture unbound, as you're binding only the color.

So solution: Store renderingData.cameraData.renderer.cameraDepthTarget into variable, then every time you call SetRenderTarget() and such call the overload with depth: cmd.SetRenderTarget(destination, rememberedDepthStencilVar);

Interesting find @babon -- do you have an example of the modified shader code from OP that can make this work?