unity实现远视角场景细节

问题：

当我们处理一些远视角的，并且物体时细长的（如远方球场的边界）渲染时。会出现一些线段丢失，并且移动视角会法线线段闪烁，感觉整个线段不完整。比如类似下图：

我要实现的是把线段填充并且尽量没有锯齿，类似下图：

 

原因：

这个问题出现的原因是，远方的物体可以表达的像素会越来越少。

无论是透视视角还是正交的，只要在远方的物体可以表现得像素都是很小了。有些位置甚至一个像素都不能表达，所以就会出现像素丢失。

 

实现方式：

针对这种问题，我的解决思路是既然他没办法在一个像素表达，我就让他用多个像素表达出来。也就是对像素做四周的采样，然后看没有像素的位置四周有没接近白色像素，如果有则加上这个颜色。

这样就可以扩大一部分像素了，变为下面这样：

看上去好多了，整个线端比较连续了。

urp下核心逻辑是：

首先用一个commandbuffer来接受球场地板的渲染，我定义的是FootBallScene的tag：

commandbuffer是这样：

using System;

namespace UnityEngine.Rendering.Universal.Internal
{
    /// <summary>
    /// Render all objects that have a 'DepthOnly' pass into the given depth buffer.
    ///
    /// You can use this pass to prime a depth buffer for subsequent rendering.
    /// Use it as a z-prepass, or use it to generate a depth buffer.
    /// </summary>
    public class FootBallScenePass : ScriptableRenderPass
    {
        int kDepthBufferBits = 32;

        private RenderTargetHandle depthAttachmentHandle { get; set; }
        internal RenderTextureDescriptor descriptor { get; private set; }

        FilteringSettings m_FilteringSettings;
        string m_ProfilerTag = "FootBallScene";
        ShaderTagId m_ShaderTagId = new ShaderTagId("FootBallScene");

        /// <summary>
        /// Create the DepthOnlyPass
        /// </summary>
        public FootBallScenePass(RenderPassEvent evt, RenderQueueRange renderQueueRange, LayerMask layerMask)
        {
            m_FilteringSettings = new FilteringSettings(renderQueueRange, layerMask);
            renderPassEvent = evt;
        }

        /// <summary>
        /// Configure the pass
        /// </summary>
        public void Setup(
            RenderTextureDescriptor baseDescriptor,
            RenderTargetHandle depthAttachmentHandle)
        {
            this.depthAttachmentHandle = depthAttachmentHandle;
            baseDescriptor.colorFormat = RenderTextureFormat.ARGB4444;
            baseDescriptor.depthBufferBits = kDepthBufferBits;

            // Depth-Only pass don't use MSAA
            baseDescriptor.msaaSamples = 1;
            descriptor = baseDescriptor;
        }

        public override void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescriptor)
        {
            cmd.GetTemporaryRT(depthAttachmentHandle.id, descriptor, FilterMode.Point);
            ConfigureTarget(depthAttachmentHandle.Identifier());
            ConfigureClear(ClearFlag.All, Color.black);
        }

        /// <inheritdoc/>
        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            CommandBuffer cmd = CommandBufferPool.Get(m_ProfilerTag);
            using (new ProfilingSample(cmd, m_ProfilerTag))
            {
                context.ExecuteCommandBuffer(cmd);
                cmd.Clear();

                var sortFlags = renderingData.cameraData.defaultOpaqueSortFlags;
                var drawSettings = CreateDrawingSettings(m_ShaderTagId, ref renderingData, sortFlags);
                drawSettings.perObjectData = PerObjectData.None;

                ref CameraData cameraData = ref renderingData.cameraData;
                Camera camera = cameraData.camera;
                if (cameraData.isStereoEnabled)
                    context.StartMultiEye(camera);

                context.DrawRenderers(renderingData.cullResults, ref drawSettings, ref m_FilteringSettings);

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

        /// <inheritdoc/>
        public override void FrameCleanup(CommandBuffer cmd)
        {
            if (cmd == null)
                throw new ArgumentNullException("cmd");

            if (depthAttachmentHandle != RenderTargetHandle.CameraTarget)
            {
                cmd.ReleaseTemporaryRT(depthAttachmentHandle.id);
                depthAttachmentHandle = RenderTargetHandle.CameraTarget;
            }
        }
    }
}

然后shader是加一个pass：

Pass
        {
            Name "FootBallScene"
            Tags{"LightMode" = "FootBallScene"}

            ZWrite On
            ColorMask RGB
            Cull Off

            HLSLPROGRAM
            // Required to compile gles 2.0 with standard srp library
            #pragma prefer_hlslcc gles
            #pragma exclude_renderers d3d11_9x
            #pragma target 2.0

            #pragma vertex FootBallSceneVertex
            #pragma fragment FootBallSceneFragment

            #include "UnlitInput.hlsl"

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

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

            Varyings FootBallSceneVertex(Attributes input)
            {
                Varyings output = (Varyings)0;

                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.vertex = vertexInput.positionCS;
                output.uv = TRANSFORM_TEX(input.uv, _BaseMap);

                return output;
            }

            half4 FootBallSceneFragment(Varyings input) : SV_Target
            {
                return SampleAlbedoAlpha(input.uv, TEXTURE2D_ARGS(_BaseMap, sampler_BaseMap));
            }
            ENDHLSL
        }

这样就拿到了我们的场景图了。

第二步就是要获取他的z轴信息，我的思想是类似获取深度图，但我是自己算了一遍符合自己的，我用相机的世界坐标和当前像素的世界坐标的距离做为深度信息：

commandbuffer其实差不多：

using System;

namespace UnityEngine.Rendering.Universal.Internal
{
    /// <summary>
    /// Render all objects that have a 'DepthOnly' pass into the given depth buffer.
    ///
    /// You can use this pass to prime a depth buffer for subsequent rendering.
    /// Use it as a z-prepass, or use it to generate a depth buffer.
    /// </summary>
    public class PosZPass : ScriptableRenderPass
    {
        int kDepthBufferBits = 32;

        private RenderTargetHandle depthAttachmentHandle { get; set; }
        internal RenderTextureDescriptor descriptor { get; private set; }

        FilteringSettings m_FilteringSettings;
        string m_ProfilerTag = "Pos Z";
        ShaderTagId m_ShaderTagId = new ShaderTagId("PosZ");

        /// <summary>
        /// Create the DepthOnlyPass
        /// </summary>
        public PosZPass(RenderPassEvent evt, RenderQueueRange renderQueueRange, LayerMask layerMask)
        {
            m_FilteringSettings = new FilteringSettings(renderQueueRange, layerMask);
            renderPassEvent = evt;
        }

        /// <summary>
        /// Configure the pass
        /// </summary>
        public void Setup(
            RenderTextureDescriptor baseDescriptor,
            RenderTargetHandle depthAttachmentHandle)
        {
            this.depthAttachmentHandle = depthAttachmentHandle;
            baseDescriptor.colorFormat = RenderTextureFormat.ARGB4444;
            baseDescriptor.depthBufferBits = kDepthBufferBits;

            // Depth-Only pass don't use MSAA
            baseDescriptor.msaaSamples = 1;
            descriptor = baseDescriptor;
        }

        public override void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescriptor)
        {
            cmd.GetTemporaryRT(depthAttachmentHandle.id, descriptor, FilterMode.Point);
            ConfigureTarget(depthAttachmentHandle.Identifier());
            ConfigureClear(ClearFlag.All, Color.black);
        }

        /// <inheritdoc/>
        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            CommandBuffer cmd = CommandBufferPool.Get(m_ProfilerTag);
            using (new ProfilingSample(cmd, m_ProfilerTag))
            {
                context.ExecuteCommandBuffer(cmd);
                cmd.Clear();

                var sortFlags = renderingData.cameraData.defaultOpaqueSortFlags;
                var drawSettings = CreateDrawingSettings(m_ShaderTagId, ref renderingData, sortFlags);
                drawSettings.perObjectData = PerObjectData.None;

                ref CameraData cameraData = ref renderingData.cameraData;
                Camera camera = cameraData.camera;
                if (cameraData.isStereoEnabled)
                    context.StartMultiEye(camera);

                context.DrawRenderers(renderingData.cullResults, ref drawSettings, ref m_FilteringSettings);

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

        /// <inheritdoc/>
        public override void FrameCleanup(CommandBuffer cmd)
        {
            if (cmd == null)
                throw new ArgumentNullException("cmd");

            if (depthAttachmentHandle != RenderTargetHandle.CameraTarget)
            {
                cmd.ReleaseTemporaryRT(depthAttachmentHandle.id);
                depthAttachmentHandle = RenderTargetHandle.CameraTarget;
            }
        }
    }
}

然后shader加一个pass：

Pass
        {
            Name "PosZ"
            Tags{"LightMode" = "PosZ"}

            ZWrite On
            ColorMask RGB
            Cull Off

            HLSLPROGRAM
            // Required to compile gles 2.0 with standard srp library
            #pragma prefer_hlslcc gles
            #pragma exclude_renderers d3d11_9x
            #pragma target 2.0

            #pragma vertex PosZVertex
            #pragma fragment PosZFragment

            #include "UnlitInput.hlsl"

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

            struct Varyings
            {
                float2 uv        : TEXCOORD0;
                float4 vertex : SV_POSITION;
                float3 vertexW : TEXCOORD1;
            };

            half4 _CameraPos;

            Varyings PosZVertex(Attributes input)
            {
                Varyings output = (Varyings)0;

                VertexPositionInputs vertexInput = GetVertexPositionInputs(input.positionOS.xyz);
                output.vertex = vertexInput.positionCS;
                output.vertexW = vertexInput.positionWS;
                output.uv = TRANSFORM_TEX(input.uv, _BaseMap);

                return output;
            }

            half4 PosZFragment(Varyings input) : SV_Target
            {
                return half4(distance(_CameraPos, input.vertexW) / 200,0,0, 1);
            }
            ENDHLSL
        }

    }

这样就能得到这个图的信息了。

场景图：

深度图：

然后我们需要知道哪些部分需要扩大像素，一般我们可以自定义，我是定义了深度在大于我的场景的0.2的时候做处理。然后用blit的方式来实现像素写入：

cmd.Blit(source, opaqueColorRT, blurMat, 0);

但是这里还有个问题，就是我们的线段还是有比较明显的锯齿感，那么我们就应该对他做一些模糊的处理，所以我们又做多了一个pass来把他变模糊。

整体的commandbuffer是：

using System;

namespace UnityEngine.Rendering.Universal.Internal
{
    /// <summary>
    /// Render all objects that have a 'DepthOnly' pass into the given depth buffer.
    ///
    /// You can use this pass to prime a depth buffer for subsequent rendering.
    /// Use it as a z-prepass, or use it to generate a depth buffer.
    /// </summary>
    public class FootBallScenePostProgressPass : ScriptableRenderPass
    {
        private Material blurMat = null;
        private RenderTexture mCurrPreRt;
        int m_SampleOffsetShaderHandle;
        Downsampling m_DownsamplingMethod;

        private RenderTargetIdentifier source { get; set; }
        private RenderTargetHandle destination { get; set; }
        const string m_ProfilerTag = "FootBallScenePostProgressPass";

        /// <summary>
        /// Create the CopyColorPass
        /// </summary>
        public FootBallScenePostProgressPass(RenderPassEvent evt)
        {
            m_SampleOffsetShaderHandle = Shader.PropertyToID("_SampleOffset");
            renderPassEvent = evt;
            m_DownsamplingMethod = Downsampling.None;
            if (mCurrPreRt != null)
            {
                mCurrPreRt.DiscardContents();
                mCurrPreRt.Release();
                RenderTexture.ReleaseTemporary(mCurrPreRt);
            }
        }

        /// <summary>
        /// Configure the pass with the source and destination to execute on.
        /// </summary>
        /// <param name="source">Source Render Target</param>
        /// <param name="destination">Destination Render Target</param>
        public void Setup(RenderTargetIdentifier source, RenderTargetHandle destination, Downsampling downsampling)
        {
            this.source = source;
            this.destination = destination;
            m_DownsamplingMethod = downsampling;
        }

        public override void Configure(CommandBuffer cmd, RenderTextureDescriptor cameraTextureDescripor)
        {
            RenderTextureDescriptor descriptor = cameraTextureDescripor;
            descriptor.msaaSamples = 1;
            descriptor.depthBufferBits = 0;
            if (m_DownsamplingMethod == Downsampling._2xBilinear)
            {
                descriptor.width /= 2;
                descriptor.height /= 2;
            }
            else if (m_DownsamplingMethod == Downsampling._4xBox || m_DownsamplingMethod == Downsampling._4xBilinear)
            {
                descriptor.width /= 4;
                descriptor.height /= 4;
            }

            cmd.GetTemporaryRT(destination.id, descriptor, m_DownsamplingMethod == Downsampling.None ? FilterMode.Point : FilterMode.Bilinear);
        }

        /// <inheritdoc/>
        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            CommandBuffer cmd = CommandBufferPool.Get(m_ProfilerTag);
            RenderTargetIdentifier opaqueColorRT = destination.Identifier();

            ref CameraData cameraData = ref renderingData.cameraData;

            if (mCurrPreRt == null)
            {
                blurMat = new Material(Shader.Find("Hidden/VT_Blur"));
                mCurrPreRt = RenderTexture.GetTemporary(cameraData.camera.pixelWidth, cameraData.camera.pixelHeight, 0,
                        RenderTextureFormat.ARGB4444);
            }

            cmd.Blit(source, mCurrPreRt, blurMat, 0);
            //cmd.Blit(mCurrPreRt, opaqueColorRT, blurMat, 1);
            //Blit(cmd, source, mCurrPreRt, blurMat, 0);
            Blit(cmd, mCurrPreRt, opaqueColorRT, blurMat, 1);

            mCurrPreRt.DiscardContents();
            mCurrPreRt.Release();

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

        /// <inheritdoc/>
        public override void FrameCleanup(CommandBuffer cmd)
        {
            if (cmd == null)
                throw new ArgumentNullException("cmd");

            if (destination != RenderTargetHandle.CameraTarget)
            {
                cmd.ReleaseTemporaryRT(destination.id);
                destination = RenderTargetHandle.CameraTarget;
            }
        }
    }
}

然后shader实现整体是：

Shader "Hidden/VT_Blur" {
    Properties{
        _MainTex("Albedo Tex", 2D) = "white" {}
        _TintColor("TintColor",color) = (1,1,1,1)
    }

        Subshader{

            Tags{ "RenderType" = "Transparent" "Queue" = "Transparent" "IgnoreProjector" = "true" }

            Pass
            {
                Blend One Zero
                CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag

                #include "UnityCG.cginc"

                sampler2D _FootballTexture;
                sampler2D _CameraPosZTexture;
                CBUFFER_START(UnityPerMaterial)
                float4 _FootballTexture_ST;
                float4 _FootballTexture_TexelSize;
                CBUFFER_END

                struct appdata
                {
                    float4 vertex : POSITION;
                    float2 texcoord : TEXCOORD0;
                };
                struct v2f
                {
                    float4 vertex : SV_POSITION;
                    float2 disuv : TEXCOORD0;
                    float4 vertexV : TEXCOORD1;
                    float4 uv01 : TEXCOORD2;
                    float4 uv23 : TEXCOORD3;
                };
                v2f vert(appdata v)
                {
                    v2f o;

                    o.vertex = UnityObjectToClipPos(v.vertex);
                    o.disuv = TRANSFORM_TEX(v.texcoord, _FootballTexture);

                    o.vertexV = mul(UNITY_MATRIX_V, mul(unity_ObjectToWorld, v.vertex));

//#if UNITY_UV_STARTS_AT_TOP  
//                    o.disuv.y = 1 - o.disuv.y;
//#endif 
                    half4 _offsets = o.vertexV.y * 2 * _FootballTexture_TexelSize.xyxy;
                    o.uv01 = o.disuv.xyxy + _offsets.xyxy * float4(1, 1, -1, -1);
                    o.uv23 = o.disuv.xyxy + _offsets.xyxy * float4(1, 0, -1, 0);
                    return o;
                }
                float4 frag(v2f i) : SV_Target
                {
                    half4 posTex = tex2D(_CameraPosZTexture, i.disuv);
                    half4 mainTex = tex2D(_FootballTexture, i.disuv);
                    half posR = 1;//posTex.r + 0.2;
                    if (posTex.r > 0.2)
                    {
                        half4 mainTex01xy = tex2D(_FootballTexture, i.uv01.xy);
                        half4 mainTex01zw = tex2D(_FootballTexture, i.uv01.zw);
                        half4 mainTex23xy = tex2D(_FootballTexture, i.uv23.xy);
                        half4 mainTex23zw = tex2D(_FootballTexture, i.uv23.zw);

                        float edge = 0.2;
                        half4 color = half4(0, 0, 0, 0);
                        if (mainTex01xy.r > edge &&
                            mainTex01xy.g > edge &&
                            mainTex01xy.b > edge)
                        {
                            color += mainTex01xy * posR;
                        }
                        if (mainTex01zw.r > edge &&
                            mainTex01zw.g > edge &&
                            mainTex01zw.b > edge)
                        {
                            color += mainTex01zw * posR;
                        }
                        if (mainTex23xy.r > edge &&
                            mainTex23xy.g > edge &&
                            mainTex23xy.b > edge)
                        {
                            color += mainTex23xy * posR;
                        }
                        if (mainTex23zw.r > edge &&
                            mainTex23zw.g > edge &&
                            mainTex23zw.b > edge)
                        {
                            color += mainTex23xy * posR;
                        }

                        return color;
                    }
                    
                    return half4(0,0,0,0);//half4(i.vertexV.y, 0,0,1);
                }
                ENDCG
            }
            Pass
            {
                Blend One Zero
                ZWrite Off
                CGPROGRAM
                #pragma vertex vert
                #pragma fragment frag

                #include "UnityCG.cginc"

            sampler2D _CameraPosZTexture;
                sampler2D _MainTex;
                CBUFFER_START(UnityPerMaterial)
                float4 _MainTex_ST;
                float4 _MainTex_TexelSize;
                float _SceneZBlurIntensity;
                CBUFFER_END

                struct appdata
                {
                    float4 vertex : POSITION;
                    float2 texcoord : TEXCOORD0;
                };
                struct v2f
                {
                    float4 vertex : SV_POSITION;
                    float2 disuv : TEXCOORD0;
                    float4 vertexV : TEXCOORD1;
                    float4 uv01 : TEXCOORD2;
                    float4 uv23 : TEXCOORD3;
                    float4 uv45 : TEXCOORD4;
                };
                v2f vert(appdata v)
                {
                    v2f o;

                    o.vertex = UnityObjectToClipPos(v.vertex);

                    o.vertexV = mul(unity_ObjectToWorld, v.vertex);
                    o.disuv = TRANSFORM_TEX(v.texcoord, _MainTex);
                    half4 _offsets = 1 * _MainTex_TexelSize.xyxy;
                    o.uv01 = o.disuv.xyxy + _offsets.xyxy * float4(1, 1, -1, -1);
                    o.uv23 = o.disuv.xyxy + _offsets.xyxy * float4(1, 1, -1, -1) * 2.0;
                    o.uv45 = o.disuv.xyxy + _offsets.xyxy * float4(1, 1, -1, -1) * 3.0;

                    return o;
                }
                float4 frag(v2f i) : SV_Target
                {
                    half4 color = float4(0, 0, 0, 0);
                    color += 0.40 * tex2D(_MainTex, i.disuv);
                    color += 0.15 * tex2D(_MainTex, i.uv01.xy);
                    color += 0.15 * tex2D(_MainTex, i.uv01.zw);
                    color += 0.10 * tex2D(_MainTex, i.uv23.xy);
                    color += 0.10 * tex2D(_MainTex, i.uv23.zw);
                    color += 0.05 * tex2D(_MainTex, i.uv45.xy);
                    color += 0.05 * tex2D(_MainTex, i.uv45.zw);

                    return half4(color.rgb * _SceneZBlurIntensity, 1);
                }

                ENDCG
            }

        }
}

最终的效果是：

 

当然这里四边的扩大和模糊都多了很多采样，消耗是多一点。如果想消耗低点可以用比较美那么多消耗的方式，比如简单的均值模糊之类的。

 

本文地址：https://blog.csdn.net/llsansun/article/details/110143360