[游戏开发] Unity SRP初识之URP

URP是Unity基于SRP提供的兼顾表现与性能的渲染管线。URP前身命名为LWRP（轻量级渲染管线），后更名为URP。

URP已包含在新建工程的工程模板中

URP使用简化的基于物理的照明和材质来实现高质量的快速渲染。
URP使用单遍正向渲染，以在多个平台上优化实时性能

官方配置说明文档：

https://docs.unity3d.com/Packages/com.unity.render-pipelines.universal@11.0/manual/universalrp-asset.html

BaseCamera与Overlay相机

URP支持两种RenderType不同的相机类型：Base与Overlay
Overlay相机渲染在Base相机在上，用于实现UI上的3D显示
Overlay相机必须加到BaseCamera上的Stack上，才能生效
Overlay相机不能应用post-processing

Post-processing

UPR实现了自己的后处理：Volume组件
手机友好的后处理
- Bloom (with High Quality Filtering disabled)
- Chromatic Aberration 色差
- Color Grading
- Lens Distortion 镜头失真
- Vignette 插图
景深：
- 在低端机上使用高斯景深（ Gaussian Depth of Field）
- 在桌面平台使用散景景深（Bokeh Depth of Field）
抗锯齿：建议使用FXAA

Shader与材质球

官方文档

URP使用与内置渲染管线不一致的着色方法，因此内置光照与自定义光照着色器（Lit Shader）不能在URP中使用。URP有自己一套Lit Shader。
内置管线的Unlit Shader（非光照Shader）仍然可以在URP中使用
可以在所有平台使用URP的Lit Shader。Lit Shader基于PBR。在URP中，Standard Shader和Standard (Specular setup) Shaders 会被指向URP的Lit Shader
非PBR可以使用Simple Lit shader,
不需要实时光照，可以使用Baked Lit Shader

// This shader draws a texture?on?the mesh.

Shader?"Example/URPUnlitShaderTexture"

{

????// The _BaseMap variable is visible in the Material's Inspector,?as a field

????// called Base Map.

????Properties

????{

????????_BaseMap("Base Map",?2D) =?"white"

????}

????SubShader

????{

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

????????Pass

????????{

????????????HLSLPROGRAM

????????????#pragma vertex vert

????????????#pragma fragment frag

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

????????????struct Attributes

????????????{

????????????????float4 positionOS???:?POSITION;

????????????????// The uv variable contains the UV coordinate?on?the texture for the

????????????????// given vertex.

????????????????float2 uv???????????:?TEXCOORD0;

????????????};

????????????struct Varyings

????????????{

????????????????float4 positionHCS??:?SV_POSITION;

????????????????// The uv variable contains the UV coordinate?on?the texture for the

????????????????// given vertex.

????????????????float2 uv???????????:?TEXCOORD0;

????????????};

????????????// This macro declares _BaseMap as a Texture2D object.

????????????TEXTURE2D(_BaseMap);

????????????// This macro declares the sampler for the _BaseMap texture.

????????????SAMPLER(sampler_BaseMap);

????????????CBUFFER_START(UnityPerMaterial)

????????????????// The following line declares the _BaseMap_ST variable,?so that you

????????????????// can use the _BaseMap variable in the fragment shader. The _ST

????????????????// suffix is necessary for the tiling and offset function to work.

????????????????float4 _BaseMap_ST;

????????????CBUFFER_END

????????????Varyings vert(Attributes IN)

????????????{

????????????????Varyings OUT;

????????????????OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);

????????????????// The TRANSFORM_TEX macro performs the tiling and offset

????????????????// transformation.

????????????????OUT.uv = TRANSFORM_TEX(IN.uv,?_BaseMap);

????????????????return OUT;

????????????}

????????????half4 frag(Varyings IN)?:?SV_Target

????????????{

????????????????// The SAMPLE_TEXTURE2D marco samples the texture with the given

????????????????// sampler.

????????????????half4 color = SAMPLE_TEXTURE2D(_BaseMap,?sampler_BaseMap,?IN.uv);

????????????????return color;

????????????}

????????????ENDHLSL

????????}

????}

}

需要额外声明TextureObj

TEXTURE2D(_BaseMap);

贴图采样器的声明

SAMPLER(sampler_BaseMap);

CBUFFER

CBUFFER_START(UnityPerMaterial)

????// The following line declares the _BaseMap_ST variable,?so that you

????// can use the _BaseMap variable in the fragment shader. The _ST

????// suffix is necessary for the tiling and offset function to work.

????float4 _BaseMap_ST;

CBUFFER_END

顶点函数中物体空间到裁剪空间的转换

OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);

UV的计算

OUT.uv = TRANSFORM_TEX(IN.uv,?_BaseMap);

贴图采样

half4 color = SAMPLE_TEXTURE2D(_BaseMap,?sampler_BaseMap,?IN.uv);