Unity URP Fullscreen 全屏特效 绘制全屏四边面并重建世界空间位置

在URP中我们可以插入自己的RenderFeature来实现一些特殊的效果。

首先我们需要创建两个C#类，分别继承ScriptableRendererFeature、ScriptableRenderPass。

这里我创建了TestRenderFeature 和TestPass。

我在TestRenderFeature的Create方法中初始化TestPass，在AddRenderPasses中调用renderer.EnqueuePass(_testPass);执行相关的渲染操作。

TestRenderFeature.cs

    public class TestRenderFeature : ScriptableRendererFeature{public Material _material;private TestPass _testPass;public override void Create(){if (_material== null){Debug.LogError("material can't be null");}_testPass=new TestPass (_material);}public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData){renderer.EnqueuePass(_testPass);}}

TestPass.cs

public class TestPass : ScriptableRenderPass
{const string m_ProfilerTag = "Test Pass";private Material material;public TestPass (Material material){this.material = material;renderPassEvent = RenderPassEvent.AfterRenderingTransparents;// 设置Pass插入的位置}public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData){if (material == null)return;var camera = renderingData.cameraData.camera;var cmd = CommandBufferPool.Get(m_ProfilerTag);///以下为绘制全屏四边面的代码/cmd.SetViewProjectionMatrices(Matrix4x4.identity, Matrix4x4.identity);cmd.DrawMesh(RenderingUtils.fullscreenMesh, Matrix4x4.identity, material);cmd.SetViewProjectionMatrices(camera.worldToCameraMatrix, camera.projectionMatrix);context.ExecuteCommandBuffer(cmd);CommandBufferPool.Release(cmd);}
}

Shader相关代码

使用GetPositionInput，传入屏幕坐标、屏幕尺寸的倒数、原始深度、UNITY_MATRIX_I_VP、UNITY_MATRIX_V，返回一个PositionInputs类型的结构体，结构体内包含世界空间坐标(positionWS)、归一化的屏幕坐标positionNDC、线性深度linearDepth。

这个函数定义在com.unity.render-pipelines.core\ShaderLibrary\Common.hlsl，我使用的版本为8.2.0

Pass{ZTest AlwaysZWrite Off//用HLSL吧HLSLPROGRAM#pragma vertex vert#pragma fragment frag//记得引入这个头文件#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DeclareDepthTexture.hlsl"struct appdata{float4 vertex : POSITION;float2 uv : TEXCOORD0;};struct v2f{float2 uv : TEXCOORD0;float4 vertex : SV_POSITION;};v2f vert (appdata v){v2f o;o.vertex = TransformObjectToHClip(v.vertex);//uv直接传过去即可o.uv=v.uv;return o;}float4 frag (v2f i) : SV_Target{float depth = LoadSceneDepth(i.uv*_ScreenParams.xy);//PositionInputs GetPositionInput(float2 positionSS, float2 invScreenSize, float deviceDepth,float4x4 invViewProjMatrix, float4x4 viewMatrix)//这里的i.uv实际上相当于归一化的屏幕坐标，让它乘以屏幕尺寸得到未归一化的屏幕坐标                PositionInputs inputs= GetPositionInput(i.uv * _ScreenParams.xy, _ScreenParams.zw-1, depth,UNITY_MATRIX_I_VP,UNITY_MATRIX_V);return float4(min(inputs.positionWS.x,1),min(inputs.positionWS.y,1),min(inputs.positionWS.z,1),1);}ENDHLSL}

效果图