1. Occlusion 环境光遮蔽图，在3D游戏经常会听到一个词环境光遮蔽（Ambient Occlusion）。
百度百科的说明 大概意思了解下就好。
AO是来描绘物体和物体相交或靠近的时候遮挡周围漫反射光线的效果，可以解决或改善漏光、飘和阴影不实等问题，解决或改善场景中缝隙、褶皱与墙角、角线以及细小物体等的表现不清晰问题，综合改善细节尤其是暗部阴影，增强空间的层次感、真实感，同时加强和改善画面明暗对比，增强画面的艺术性
上面的斯坦福龙呈现在一个均匀照明的环境中。 模型中有一些较黑和较亮的区域，但照明大部分都是均匀的。 尽管有相当复杂的几何形状，但龙看上去很平，没有明显的深度感觉。
下面是启用了环境光遮蔽的相同模型。
环境光遮蔽 从字面上就是对于环境光影响。对于直接光照不影响。
Unity里面实现下
1 half Occlusion(float2 uv) 2 { 3 #if (SHADER_TARGET < 30) 4 // SM20: instruction count limitation 5 // SM20: simpler occlusion 6 return tex2D(_OcclusionMap, uv).g; 7 #else 8 half occ = tex2D(_OcclusionMap, uv).g; 9 return LerpOneTo (occ, _OcclusionStrength); 10 #endif 11 }
inline UnityGI UnityGI_Base(UnityGIInput data, half occlusion, half3 normalWorld) {UnityGI o_gi;ResetUnityGI(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; }
使用的地方影响的diffuse 环境光的强度。
Detail Map Unity提供两个，一个DetailAlbedo 一个是DetailNormal
DetailAlbodo
float4 TexCoords(VertexInput v) {float4 texcoord;texcoord.xy = TRANSFORM_TEX(v.uv0, _MainTex); // Always source from uv0texcoord.zw = TRANSFORM_TEX(((_UVSec == 0) ? v.uv0 : v.uv1), _DetailAlbedoMap);return texcoord; }VertexOutputForwardBase vertForwardBase (VertexInput v) {UNITY_SETUP_INSTANCE_ID(v);VertexOutputForwardBase o;UNITY_INITIALIZE_OUTPUT(VertexOutputForwardBase, o);UNITY_TRANSFER_INSTANCE_ID(v, o);UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);float4 posWorld = mul(unity_ObjectToWorld, v.vertex);#if UNITY_REQUIRE_FRAG_WORLDPOS#if UNITY_PACK_WORLDPOS_WITH_TANGENTo.tangentToWorldAndPackedData[0].w = posWorld.x;o.tangentToWorldAndPackedData[1].w = posWorld.y;o.tangentToWorldAndPackedData[2].w = posWorld.z;#elseo.posWorld = posWorld.xyz;#endif#endifo.pos = UnityObjectToClipPos(v.vertex);o.tex = TexCoords(v);o.eyeVec = NormalizePerVertexNormal(posWorld.xyz - _WorldSpaceCameraPos);float3 normalWorld = UnityObjectToWorldNormal(v.normal);#ifdef _TANGENT_TO_WORLDfloat4 tangentWorld = float4(UnityObjectToWorldDir(v.tangent.xyz), v.tangent.w);float3x3 tangentToWorld = CreateTangentToWorldPerVertex(normalWorld, tangentWorld.xyz, tangentWorld.w);o.tangentToWorldAndPackedData[0].xyz = tangentToWorld[0];o.tangentToWorldAndPackedData[1].xyz = tangentToWorld[1];o.tangentToWorldAndPackedData[2].xyz = tangentToWorld[2];#elseo.tangentToWorldAndPackedData[0].xyz = 0;o.tangentToWorldAndPackedData[1].xyz = 0;o.tangentToWorldAndPackedData[2].xyz = normalWorld;#endif//We need this for shadow receving UNITY_TRANSFER_SHADOW(o, v.uv1);o.ambientOrLightmapUV = VertexGIForward(v, posWorld, normalWorld);#ifdef _PARALLAXMAPTANGENT_SPACE_ROTATION;half3 viewDirForParallax = mul (rotation, ObjSpaceViewDir(v.vertex));o.tangentToWorldAndPackedData[0].w = viewDirForParallax.x;o.tangentToWorldAndPackedData[1].w = viewDirForParallax.y;o.tangentToWorldAndPackedData[2].w = viewDirForParallax.z;#endifUNITY_TRANSFER_FOG(o,o.pos);return o; }
在顶点着色器的 先填充UV
o.tex = TexCoords(v);
像素着色器
inline FragmentCommonData RoughnessSetup(float4 i_tex) {half2 metallicGloss = MetallicRough(i_tex.xy);half metallic = metallicGloss.x;half smoothness = metallicGloss.y; // this is 1 minus the square root of real roughness m. half oneMinusReflectivity;half3 specColor;half3 diffColor = DiffuseAndSpecularFromMetallic(Albedo(i_tex), metallic, /*out*/ specColor, /*out*/ oneMinusReflectivity);FragmentCommonData o = (FragmentCommonData)0;o.diffColor = diffColor;o.specColor = specColor;o.oneMinusReflectivity = oneMinusReflectivity;o.smoothness = smoothness;return o; }
采样颜色
inline half3 DiffuseAndSpecularFromMetallic (half3 albedo, half metallic, out half3 specColor, out half oneMinusReflectivity) {specColor = lerp (unity_ColorSpaceDielectricSpec.rgb, albedo, metallic);oneMinusReflectivity = OneMinusReflectivityFromMetallic(metallic);return albedo * oneMinusReflectivity; }
half3 Albedo(float4 texcoords) {half3 albedo = _Color.rgb * tex2D (_MainTex, texcoords.xy).rgb; #if _DETAIL#if (SHADER_TARGET < 30)// SM20: instruction count limitation// SM20: no detail maskhalf mask = 1;#elsehalf mask = DetailMask(texcoords.xy);#endifhalf3 detailAlbedo = tex2D (_DetailAlbedoMap, texcoords.zw).rgb;#if _DETAIL_MULX2albedo *= LerpWhiteTo (detailAlbedo * unity_ColorSpaceDouble.rgb, mask);#elif _DETAIL_MULalbedo *= LerpWhiteTo (detailAlbedo, mask);#elif _DETAIL_ADDalbedo += detailAlbedo * mask;#elif _DETAIL_LERPalbedo = lerp (albedo, detailAlbedo, mask);#endif #endifreturn albedo; }
这里detailAlbedo有多种的混合模式。可以选择。
DetailNormal
// parallax transformed texcoord is used to sample occlusion inline FragmentCommonData FragmentSetup (inout float4 i_tex, float3 i_eyeVec, half3 i_viewDirForParallax, float4 tangentToWorld[3], float3 i_posWorld) {i_tex = Parallax(i_tex, i_viewDirForParallax);half alpha = Alpha(i_tex.xy);#if defined(_ALPHATEST_ON)clip (alpha - _Cutoff);#endifFragmentCommonData o = UNITY_SETUP_BRDF_INPUT (i_tex);o.normalWorld = PerPixelWorldNormal(i_tex, tangentToWorld);o.eyeVec = NormalizePerPixelNormal(i_eyeVec);o.posWorld = i_posWorld;// NOTE: shader relies on pre-multiply alpha-blend (_SrcBlend = One, _DstBlend = OneMinusSrcAlpha)o.diffColor = PreMultiplyAlpha (o.diffColor, alpha, o.oneMinusReflectivity, /*out*/ o.alpha);return o; }
o.normalWorld = PerPixelWorldNormal(i_tex, tangentToWorld);
在像素着色器中，计算顶点法线
float3 PerPixelWorldNormal(float4 i_tex, float4 tangentToWorld[3]) { #ifdef _NORMALMAPhalf3 tangent = tangentToWorld[0].xyz;half3 binormal = tangentToWorld[1].xyz;half3 normal = tangentToWorld[2].xyz;#if UNITY_TANGENT_ORTHONORMALIZEnormal = NormalizePerPixelNormal(normal);// ortho-normalize Tangenttangent = normalize (tangent - normal * dot(tangent, normal));// recalculate Binormalhalf3 newB = cross(normal, tangent);binormal = newB * sign (dot (newB, binormal));#endifhalf3 normalTangent = NormalInTangentSpace(i_tex);float3 normalWorld = NormalizePerPixelNormal(tangent * normalTangent.x + binormal * normalTangent.y + normal * normalTangent.z); // @TODO: see if we can squeeze this normalize on SM2.0 as well #elsefloat3 normalWorld = normalize(tangentToWorld[2].xyz); #endifreturn normalWorld; }
UNITY_TANGENT_ORTHONORMALIZE
这里正交归一化一般不开启，就是重新把法线 副法线，切线正交。但是一般的精度就够了，不需要在顶点着色器中，重新做。
half3 normalTangent = NormalInTangentSpace(i_tex);
采样出切线空间中，法线的方向。
#ifdef _NORMALMAP half3 NormalInTangentSpace(float4 texcoords) {half3 normalTangent = UnpackScaleNormal(tex2D (_BumpMap, texcoords.xy), _BumpScale);#if _DETAIL && defined(UNITY_ENABLE_DETAIL_NORMALMAP)half mask = DetailMask(texcoords.xy);half3 detailNormalTangent = UnpackScaleNormal(tex2D (_DetailNormalMap, texcoords.zw), _DetailNormalMapScale);#if _DETAIL_LERPnormalTangent = lerp(normalTangent,detailNormalTangent,mask);#elsenormalTangent = lerp(normalTangent,BlendNormals(normalTangent, detailNormalTangent),mask);#endif #endifreturn normalTangent; } #endif
这样就全部搞定。
这里有个非常重要的一点。为什么早期渲染，金属感弱的问题。
#define unity_ColorSpaceDielectricSpec half4(0.04, 0.04, 0.04, 1.0 - 0.04) // standard dielectric reflectivity coef at incident angle (= 4%)specColor = lerp (unity_ColorSpaceDielectricSpec.rgb, albedo, metallic);
根据材料的金属度不一样，高光颜色是不一样的。根据物质的导电性特性区分。可以根据龚大的这篇文章
金属，塑料，傻傻分不清楚
// parallax transformed texcoord is used to sample occlusion inline FragmentCommonData FragmentSetup (inout float4 i_tex, float3 i_eyeVec, half3 i_viewDirForParallax, float4 tangentToWorld[3], float3 i_posWorld) {i_tex = Parallax(i_tex, i_viewDirForParallax);half alpha = Alpha(i_tex.xy);#if defined(_ALPHATEST_ON)clip (alpha - _Cutoff);#endifFragmentCommonData o = UNITY_SETUP_BRDF_INPUT (i_tex);o.normalWorld = PerPixelWorldNormal(i_tex, tangentToWorld);o.eyeVec = NormalizePerPixelNormal(i_eyeVec);o.posWorld = i_posWorld;// NOTE: shader relies on pre-multiply alpha-blend (_SrcBlend = One, _DstBlend = OneMinusSrcAlpha)o.diffColor = PreMultiplyAlpha (o.diffColor, alpha, o.oneMinusReflectivity, /*out*/ o.alpha);return o; }
代码流程有点长，在顶点着色器的入口函数
half4 fragForwardBaseInternal (VertexOutputForwardBase i) {UNITY_APPLY_DITHER_CROSSFADE(i.pos.xy);FRAGMENT_SETUP(s)UNITY_SETUP_INSTANCE_ID(i);UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(i);UnityLight mainLight = MainLight ();UNITY_LIGHT_ATTENUATION(atten, i, s.posWorld);half occlusion = Occlusion(i.tex.xy);UnityGI gi = FragmentGI (s, occlusion, i.ambientOrLightmapUV, atten, mainLight);half4 c = UNITY_BRDF_PBS (s.diffColor, s.specColor, s.oneMinusReflectivity, s.smoothness, s.normalWorld, -s.eyeVec, gi.light, gi.indirect);c.rgb += Emission(i.tex.xy);UNITY_APPLY_FOG(i.fogCoord, c.rgb);return OutputForward (c, s.alpha); }
通过宏，获取基本的diff颜色和高光，法线一些基础信息
#define FRAGMENT_SETUP(x) FragmentCommonData x = \FragmentSetup(i.tex, i.eyeVec, IN_VIEWDIR4PARALLAX(i), i.tangentToWorldAndPackedData, IN_WORLDPOS(i));
inline FragmentCommonData FragmentSetup (inout float4 i_tex, float3 i_eyeVec, half3 i_viewDirForParallax, float4 tangentToWorld[3], float3 i_posWorld) {i_tex = Parallax(i_tex, i_viewDirForParallax);half alpha = Alpha(i_tex.xy);#if defined(_ALPHATEST_ON)clip (alpha - _Cutoff);#endifFragmentCommonData o = UNITY_SETUP_BRDF_INPUT (i_tex);o.normalWorld = PerPixelWorldNormal(i_tex, tangentToWorld);o.eyeVec = NormalizePerPixelNormal(i_eyeVec);o.posWorld = i_posWorld;// NOTE: shader relies on pre-multiply alpha-blend (_SrcBlend = One, _DstBlend = OneMinusSrcAlpha)o.diffColor = PreMultiplyAlpha (o.diffColor, alpha, o.oneMinusReflectivity, /*out*/ o.alpha);return o; }