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前言

Unity中Shader的GI相关数据的准备，这是基于上一篇文章中的自定义 cginc 文件的基础上续写的,主要是要把在 GI 中用到的 cginc 库，整合到自己的 cginc 文件中。

• Unity中Shader自定义cginc文件

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一、把 Unity 中用到的 GI 的函数移植到我们自定义的 cginc 文件中

我们复制过来后，可以发现缺少一些相关的函数 和 类型，我们需要依次找到后，复制在该函数上方，因为 CG 不像C#一样可以读取到后面定义的函数

下面是依次解决完没有引入方法、结构体后的 代码：(在方法后加1，是为了和Unity自带方法区别开)

#ifndef MYGLOBALILLUMINATION_INCLUDE
#define MYGLOBALILLUMINATION_INCLUDEinline void ResetUnityLight1(out UnityLight outLight)
{outLight.color = half3(0, 0, 0);outLight.dir = half3(0, 1, 0); // Irrelevant direction, just not nulloutLight.ndotl = 0; // Not used
}inline void ResetUnityGI1(out UnityGI outGI)
{ResetUnityLight1(outGI.light);outGI.indirect.diffuse = 0;outGI.indirect.specular = 0;
}inline UnityGI UnityGI_Base1(UnityGIInput data, half occlusion, half3 normalWorld)
{UnityGI o_gi;ResetUnityGI1(o_gi);// Base pass with Lightmap support is responsible for handling ShadowMask / blending here for performance reason#if defined(HANDLE_SHADOWS_BLENDING_IN_GI)half bakedAtten = UnitySampleBakedOcclusion(data.lightmapUV.xy, data.worldPos);float zDist = dot(_WorldSpaceCameraPos - data.worldPos, UNITY_MATRIX_V[2].xyz);float fadeDist = UnityComputeShadowFadeDistance(data.worldPos, zDist);data.atten = UnityMixRealtimeAndBakedShadows(data.atten, bakedAtten, UnityComputeShadowFade(fadeDist));#endifo_gi.light = data.light;o_gi.light.color *= data.atten;#if UNITY_SHOULD_SAMPLE_SHo_gi.indirect.diffuse = ShadeSHPerPixel(normalWorld, data.ambient, data.worldPos);#endif#if defined(LIGHTMAP_ON)// Baked lightmapshalf4 bakedColorTex = UNITY_SAMPLE_TEX2D(unity_Lightmap, data.lightmapUV.xy);half3 bakedColor = DecodeLightmap(bakedColorTex);#ifdef DIRLIGHTMAP_COMBINEDfixed4 bakedDirTex = UNITY_SAMPLE_TEX2D_SAMPLER (unity_LightmapInd, unity_Lightmap, data.lightmapUV.xy);o_gi.indirect.diffuse += DecodeDirectionalLightmap (bakedColor, bakedDirTex, normalWorld);#if defined(LIGHTMAP_SHADOW_MIXING) && !defined(SHADOWS_SHADOWMASK) && defined(SHADOWS_SCREEN)ResetUnityLight(o_gi.light);o_gi.indirect.diffuse = SubtractMainLightWithRealtimeAttenuationFromLightmap (o_gi.indirect.diffuse, data.atten, bakedColorTex, normalWorld);#endif#else // not directional lightmapo_gi.indirect.diffuse += bakedColor;#if defined(LIGHTMAP_SHADOW_MIXING) && !defined(SHADOWS_SHADOWMASK) && defined(SHADOWS_SCREEN)ResetUnityLight(o_gi.light);o_gi.indirect.diffuse = SubtractMainLightWithRealtimeAttenuationFromLightmap(o_gi.indirect.diffuse, data.atten, bakedColorTex, normalWorld);#endif#endif#endif#ifdef DYNAMICLIGHTMAP_ON// Dynamic lightmapsfixed4 realtimeColorTex = UNITY_SAMPLE_TEX2D(unity_DynamicLightmap, data.lightmapUV.zw);half3 realtimeColor = DecodeRealtimeLightmap (realtimeColorTex);#ifdef DIRLIGHTMAP_COMBINEDhalf4 realtimeDirTex = UNITY_SAMPLE_TEX2D_SAMPLER(unity_DynamicDirectionality, unity_DynamicLightmap, data.lightmapUV.zw);o_gi.indirect.diffuse += DecodeDirectionalLightmap (realtimeColor, realtimeDirTex, normalWorld);#elseo_gi.indirect.diffuse += realtimeColor;#endif#endifo_gi.indirect.diffuse *= occlusion;return o_gi;
}inline UnityGI UnityGlobalIllumination1 (UnityGIInput data, half occlusion, half3 normalWorld)
{return UnityGI_Base1(data, occlusion, normalWorld);
}inline void LightingLambert_GI1 (SurfaceOutput s,UnityGIInput data,inout UnityGI gi)
{gi = UnityGlobalIllumination1 (data, 1.0, s.Normal);
}#endif

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二、开始使用和 GI 相关的方法

1、了解 UnityGI 结构体的内容,并且准备 UnityGI 的数据

因为 GI = 直接光照 + 间接光照，所以UnityGI中的内容是存储一些相关的信息

准备 UnityGI 的数据

	//3、准备 UnityGI 的数据UnityGI gi;//直接光照数据（主平行光）gi.light.color = _LightColor0;gi.light.dir = _WorldSpaceLightPos0;//间接光照数据(目前先给0)gi.indirect.diffuse = 0;gi.indirect.specular = 0;

2、了解 SurfaceOutput 结构体，并且准备数据

该结构体主要存储 和物体表面相关的主要信息

准备 SurfaceOutput 数据

	//1、准备 SurfaceOutput 的数据SurfaceOutput o;//目前先初始化为0，使用Unity自带的方法，把结构体中的内容初始化为0UNITY_INITIALIZE_OUTPUT(SurfaceOutput,o)

3、了解并准备 UnityGIInput 结构体，并且准备其相关数据

主要是用来计算 GI 的相关数据

准备UnityGIInput数据

	//2、准备 UnityGIInput 的数据UnityGIInput giInput;//初始化UNITY_INITIALIZE_OUTPUT(UnityGIInput,giInput);//修改用到的数据giInput.light.color = _LightColor0;giInput.light.dir = _WorldSpaceLightPos0;giInput.worldPos = i.worldPos;giInput.worldViewDir = normalize(_WorldSpaceCameraPos - i.worldPos);giInput.atten = 1;giInput.ambient = 0;//giInput.lightmapUV = ?

这是目前准备完 GI 数据的代码

//在这里里面使用 自定义的 cginc 来实现全局GI
Shader "MyShader/P1_8_2"
{SubShader{Tags { "RenderType"="Opaque" }Pass{CGPROGRAM#pragma vertex vert#pragma fragment frag#include "UnityCG.cginc"#include "AutoLight.cginc"#include "Lighting.cginc"#include "CGIncludes/MyGlobalIllumination.cginc"struct appdata{float4 vertex : POSITION;};struct v2f{float4 vertex : SV_POSITION;float4 worldPos : TEXCOORD0;};v2f vert (appdata v){v2f o;o.vertex = UnityObjectToClipPos(v.vertex);o.worldPos = mul(unity_ObjectToWorld,v.vertex);return o;}fixed4 frag (v2f i) : SV_Target{//1、准备 SurfaceOutput 的数据SurfaceOutput o;//目前先初始化为0，使用Unity自带的方法，把结构体中的内容初始化为0UNITY_INITIALIZE_OUTPUT(SurfaceOutput,o)//2、准备 UnityGIInput 的数据UnityGIInput giInput;//初始化UNITY_INITIALIZE_OUTPUT(UnityGIInput,giInput);//修改用到的数据giInput.light.color = _LightColor0;giInput.light.dir = _WorldSpaceLightPos0;giInput.worldPos = i.worldPos;giInput.worldViewDir = normalize(_WorldSpaceCameraPos - i.worldPos);giInput.atten = 1;giInput.ambient = 0;//giInput.lightmapUV = ?//3、准备 UnityGI 的数据UnityGI gi;//直接光照数据（主平行光）gi.light.color = _LightColor0;gi.light.dir = _WorldSpaceLightPos0;//间接光照数据(目前先给0)gi.indirect.diffuse = 0;gi.indirect.specular = 0;LightingLambert_GI1(o,giInput,gi);return 1;}ENDCG}}
}