《Unity Shader 入门精要》从Bulit-in 到URP （HLSL）Chapter13.3-基于深度纹理的雾效（屏幕后措置）
前言：已经进入“高级篇”啦，但愿大师多多撑持，多多存眷，这将对我发生非常愉悦的正反馈~
“《Unity Shader 入门精要》从Bulit-in 到URP”是一个辅佐Unity Shader学习者以冯乐乐女神《Unity Shader 入门精要》为基础学习用HLSL语言编写URP着色器的案例教学系列。
作者自学能力有限，抛砖引玉，如有建议和问题请各位大佬和同仁交流斧正。
如安在URP中实现后措置参见：
Bulit-in版：
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'
Shader ”Unity Shaders Book/Chapter 13/Fog With Depth Texture” {
Properties {
_MainTex (”Base (RGB)”, 2D) = ”white” {}
_FogDensity (”Fog Density”, Float) = 1.0
_FogColor (”Fog Color”, Color) = (1, 1, 1, 1)
_FogStart (”Fog Start”, Float) = 0.0
_FogEnd (”Fog End”, Float) = 1.0
}
SubShader {
CGINCLUDE
#include ”UnityCG.cginc”
float4x4 _FrustumCornersRay;
sampler2D _MainTex;
half4 _MainTex_TexelSize;
sampler2D _CameraDepthTexture;
half _FogDensity;
fixed4 _FogColor;
float _FogStart;
float _FogEnd;
struct v2f {
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
half2 uv_depth : TEXCOORD1;
float4 interpolatedRay : TEXCOORD2;
};
v2f vert(appdata_img v) {
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv = v.texcoord;
o.uv_depth = v.texcoord;
#if UNITY_UV_STARTS_AT_TOP
if (_MainTex_TexelSize.y < 0)
o.uv_depth.y = 1 - o.uv_depth.y;
#endif
int index = 0;
if (v.texcoord.x < 0.5 && v.texcoord.y < 0.5) {
index = 0;
} else if (v.texcoord.x > 0.5 && v.texcoord.y < 0.5) {
index = 1;
} else if (v.texcoord.x > 0.5 && v.texcoord.y > 0.5) {
index = 2;
} else {
index = 3;
}
#if UNITY_UV_STARTS_AT_TOP
if (_MainTex_TexelSize.y < 0)
index = 3 - index;
#endif
o.interpolatedRay = _FrustumCornersRay;
return o;
}
fixed4 frag(v2f i) : SV_Target {
float linearDepth = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, i.uv_depth));
float3 worldPos = _WorldSpaceCameraPos + linearDepth * i.interpolatedRay.xyz;
float fogDensity = (_FogEnd - worldPos.y) / (_FogEnd - _FogStart);
fogDensity = saturate(fogDensity * _FogDensity);
fixed4 finalColor = tex2D(_MainTex, i.uv);
finalColor.rgb = lerp(finalColor.rgb, _FogColor.rgb, fogDensity);
return finalColor;
}
ENDCG
Pass {
ZTest Always Cull Off ZWrite Off
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
ENDCG
}
}
FallBack Off
}
URP版：
Unity项目源码：
Shader ”Unlit/Chapter13-FogWithDepthTexture”
{
Properties {
_MainTex (”Base (RGB)”, 2D) = ”white” {}
_FogDensity (”Fog Density”, Float) = 1.0
_FogColor (”Fog Color”, Color) = (1, 1, 1, 1)
_FogStart (”Fog Start”, Float) = 0.0
_FogEnd (”Fog End”, Float) = 1.0
}
SubShader
{
Tags { ”RenderPipeline” = ”UniversalPipeline” }
HLSLINCLUDE
#include ”Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl”
#include ”Packages/com.unity.render-pipelines.universal/ShaderLibrary/Lighting.hlsl”
CBUFFER_START(UnityPerMaterial)
float4x4 _FrustumCornersRay;
half4 _MainTex_TexelSize;
half _FogDensity;
half4 _FogColor;
float _FogStart;
float _FogEnd;
CBUFFER_END
TEXTURE2D(_MainTex); SAMPLER(sampler_MainTex);
TEXTURE2D(_CameraDepthTexture); SAMPLER(sampler_CameraDepthTexture);
//如果在URP Asset设置下勾选 depth texture选项系统会自动生成一张以_CameraDepthTexture为名的深度图，抽时间会写一篇相关文章并把链接补充到本篇中。
struct appdata{
float4 vertex : POSITION;
float2 texcoord : TEXCOORD0;
};
struct v2f {
float4 pos : SV_POSITION;
half2 uv : TEXCOORD0;
half2 uv_depth : TEXCOORD1;
float4 interpolatedRay : TEXCOORD2;
};
v2f vert(appdata v) {
v2f o;
o.pos = TransformObjectToHClip(v.vertex);
o.uv = v.texcoord;
o.uv_depth = v.texcoord;
#if UNITY_UV_STARTS_AT_TOP
if (_MainTex_TexelSize.y < 0)
o.uv_depth.y = 1 - o.uv_depth.y;
#endif
int index = 0;
if (v.texcoord.x < 0.5 && v.texcoord.y < 0.5) {
index = 0;
} else if (v.texcoord.x > 0.5 && v.texcoord.y < 0.5) {
index = 1;
} else if (v.texcoord.x > 0.5 && v.texcoord.y > 0.5) {
index = 2;
} else {
index = 3;
}
#if UNITY_UV_STARTS_AT_TOP
if (_MainTex_TexelSize.y < 0)
index = 3 - index;
#endif
o.interpolatedRay = _FrustumCornersRay;
//尽管我们这里使用了很多判断语句，但由于屏幕后措置所用的模型是一个四边形网格，只包含4个顶点，因此这些操作不会对性能造成很大影响。
return o;
}
half4 frag(v2f i) : SV_Target {
float linearDepth = LinearEyeDepth(SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, sampler_CameraDepthTexture,i.uv_depth), _ZBufferParams);
//使用LinearEyeDepth得到视角空间下的线性深度值
float3 worldPos = _WorldSpaceCameraPos + linearDepth * i.interpolatedRay.xyz;
float fogDensity = (_FogEnd - worldPos.y) / (_FogEnd - _FogStart);
fogDensity = saturate(fogDensity * _FogDensity);
half4 finalColor = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, i.uv);
finalColor.rgb = lerp(finalColor.rgb, _FogColor.rgb, fogDensity);
return finalColor;
}
ENDHLSL
Pass {
ZTest Always Cull Off ZWrite Off
HLSLPROGRAM
#pragma vertex vert
#pragma fragment frag
ENDHLSL
}
}
FallBack ”Packages/com.unity.render-pipelines.universal/FallbackError”
}
URP后措置脚本
因为和上面提供的（Post-processing : RenderFeature + VolumeComponent）模板有些许差异，因此在此提供对应源码。
using System;
using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;
public class FogWithDepthTexture : ScriptableRendererFeature
{
public class CustomVolumeComponent : DingVolumeComponentBase
{
public ClampedFloatParameter FogDensity = new ClampedFloatParameter(1.0f, 0, 3.0f);
public MinFloatParameter FogStart = new MinFloatParameter(0f, 0f);
public MinFloatParameter FogEnd = new MinFloatParameter(2.0f, 0f);
public ColorParameter FogColor = new ColorParameter(Color.white, false, false, true);
public override bool IsActive() => isRender.value;
public override bool IsTileCompatible() => false;
}
class CustomRenderPass : ScriptableRenderPass
{
public Material material;
private Matrix4x4 frustumCorners;
//RT的滤波模式
public FilterMode filterMode {get; set;}
//当前衬着阶段的colorRT
//RenderTargetIdentifier、RenderTargetHandle都可以理解为RT，Identifier为camera提供的需要被应用的texture，Handle为被shader措置衬着过的RT
private RenderTargetIdentifier source {get; set;}
//private RenderTargetHandle destination {get; set;}
//辅助RT
private RenderTargetHandle tempTexture;
string m_ProfilerTag;
//Profiling上显示
public CustomVolumeComponent volume;
ProfilingSampler m_ProfilingSampler = new ProfilingSampler(”URPDing”);
public CustomRenderPass(RenderPassEvent renderPassEvent, Shader shader, CustomVolumeComponent volume, string tag){
//确定在哪个阶段插入衬着
this.renderPassEvent = renderPassEvent;
this.volume = volume;
if(shader == null){return;}
this.material = CoreUtils.CreateEngineMaterial(shader);
m_ProfilerTag = tag;
//初始化辅助RT的名字
tempTexture.Init(”_TempRTexture”);
}
public void Setup(RenderTargetIdentifier source){
this.source = source;
//this.destination = destination;
}
public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
{
if (!volume.IsActive()) {
return;
}
CommandBuffer cmd = CommandBufferPool.Get(”m_ProfilerTag”);
//using 方式可以实此刻FrameDebug上查看衬着过程
using(new ProfilingScope(cmd, m_ProfilingSampler)){
Camera camera = renderingData.cameraData.camera;
//获取摄像机
Transform cameraTransform = camera.transform;
float fov = camera.fieldOfView;
float near = camera.nearClipPlane;
float far = camera.farClipPlane;
float aspect = camera.aspect;
float halfHeight = near * Mathf.Tan(fov * 0.5f * Mathf.Deg2Rad);
Vector3 toRight = cameraTransform.right * halfHeight * aspect;
Vector3 toTop = cameraTransform.up * halfHeight;
Vector3 topLeft = cameraTransform.forward * near + toTop - toRight;
float scale = topLeft.magnitude / near;
topLeft.Normalize();
topLeft *= scale;
Vector3 topRight = cameraTransform.forward * near + toRight + toTop;
topRight.Normalize();
topRight *= scale;
Vector3 bottomLeft = cameraTransform.forward * near - toTop - toRight;
bottomLeft.Normalize();
bottomLeft *= scale;
Vector3 bottomRight = cameraTransform.forward * near + toRight - toTop;
bottomRight.Normalize();
bottomRight *= scale;
frustumCorners.SetRow(0, bottomLeft);
frustumCorners.SetRow(1, bottomRight);
frustumCorners.SetRow(2, topRight);
frustumCorners.SetRow(3, topLeft);
material.SetMatrix(”_FrustumCornersRay”, frustumCorners);
material.SetMatrix(”_ViewProjectionInverseMatrix”, (camera.projectionMatrix * camera.worldToCameraMatrix).inverse);
material.SetFloat(”_FogDensity”, volume.FogDensity.value);
material.SetFloat(”_FogStart”, volume.FogStart.value);
material.SetFloat(”_FogEnd”, volume.FogEnd.value);
material.SetColor(”_FogColor”, volume.FogColor.value);
//创建一张RT
RenderTextureDescriptor cameraTextureDesc = renderingData.cameraData.cameraTargetDescriptor;
cameraTextureDesc.depthBufferBits = 0;
cameraTextureDesc.msaaSamples = 1;
//打消抗锯齿措置,抗锯齿会影响unity自动在DX与OpenGL间的坐标转换
cmd.GetTemporaryRT(tempTexture.id, cameraTextureDesc, filterMode);
//将当前帧的colorRT用着色器（shader in material）衬着后输出到之前创建的贴图（辅助RT）上
Blit(cmd, source, tempTexture.Identifier(), material, 0);
//将措置后的辅助RT从头衬着到当前帧的colorRT上
Blit(cmd, tempTexture.Identifier(), source);
}
//执行衬着
context.ExecuteCommandBuffer(cmd);
//释放回收
CommandBufferPool.Release(cmd);
}
public override void FrameCleanup(CommandBuffer cmd){
base.FrameCleanup(cmd);
cmd.ReleaseTemporaryRT(tempTexture.id);
}
}
public class Settings{
public RenderPassEvent Event = RenderPassEvent.AfterRenderingTransparents;
public Shader shader;
}
public Settings settings = new Settings();
CustomVolumeComponent volume;
CustomRenderPass m_ScriptablePass;
/// <inheritdoc/>
//feature被创建时调用
public override void Create()
{
var stack = VolumeManager.instance.stack;
volume = stack.GetComponent<CustomVolumeComponent>();
if (volume == null) {
CoreUtils.Destroy(m_ScriptablePass.material);
return;
}
m_ScriptablePass = new CustomRenderPass(settings.Event, settings.shader, volume, name);
}
//每一帧城市调用
public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
{
var src = renderer.cameraColorTarget;
//var dest = RenderTargetHandle.CameraTarget;
if(settings.shader == null){
Debug.LogWarningFormat(”shader丢掉”,GetType().Name);
return;
}
//将当前衬着的colorRT传到Pass中
m_ScriptablePass.Setup(src);
//将Pass添加到衬着队列中
renderer.EnqueuePass(m_ScriptablePass);
}
protected override void Dispose(bool disposing)
{
base.Dispose(disposing);
}
}
效果图：
因为我在sense中使用的是图片，图片上没有深度分歧，所以无法在图片上不雅察看到深度分歧的雾效区别，图片以外区域可以感到感染到稍微明显的深度雾效。
如有收获，请留下“存眷”和“附和”~
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