Unity中Shader的GI相关数据的准备

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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_INCLUDE


inline void ResetUnityLight1(out UnityLight outLight)
{
    outLight.color = half3(0, 0, 0);
    outLight.dir = half3(0, 1, 0); // Irrelevant direction, just not null
    outLight.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));
    #endif

    o_gi.light = data.light;
    o_gi.light.color *= data.atten;

    #if UNITY_SHOULD_SAMPLE_SH
        o_gi.indirect.diffuse = ShadeSHPerPixel(normalWorld, data.ambient, data.worldPos);
    #endif

    #if defined(LIGHTMAP_ON)
        // Baked lightmaps
        half4 bakedColorTex = UNITY_SAMPLE_TEX2D(unity_Lightmap, data.lightmapUV.xy);
        half3 bakedColor = DecodeLightmap(bakedColorTex);

        #ifdef DIRLIGHTMAP_COMBINED
            fixed4 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 lightmap
            o_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 lightmaps
        fixed4 realtimeColorTex = UNITY_SAMPLE_TEX2D(unity_DynamicLightmap, data.lightmapUV.zw);
        half3 realtimeColor = DecodeRealtimeLightmap (realtimeColorTex);

        #ifdef DIRLIGHTMAP_COMBINED
            half4 realtimeDirTex = UNITY_SAMPLE_TEX2D_SAMPLER(unity_DynamicDirectionality, unity_DynamicLightmap, data.lightmapUV.zw);
            o_gi.indirect.diffuse += DecodeDirectionalLightmap (realtimeColor, realtimeDirTex, normalWorld);
        #else
            o_gi.indirect.diffuse += realtimeColor;
        #endif
    #endif

    o_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0
    UNITY_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0
                UNITY_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
        }
    }
}