[TA-Frost Wolf_may-"Hundred Talents Project"] Art 2.7 Metallic and Speculer Process

2.7.1 概念

• What is the next generation model.The model baked through the high and low molds.
• 什么是pbr模型：基于物理渲染,Use different textures to combine different parameters of an objectUVcorresponding to the model

2.7.2 两种流程

常用工作流程：

1. 金属/粗糙度工作流（Metal / Roughness）
2. 镜面反射/光泽度工作流（Specular/Glossiness）
   
   选择：Metal roughness is more intuitive,Easy to adjust parameters,应用广泛,But the Fresnel reflection value cannot be adjusted;
   Specular reflection can modify the Fresnel value,But it is easy to destroy the conservation of energy;

通用贴图：

法线贴图、AO贴图、高度贴图

2.7.3 Metal/ Roughness特有贴图

base color RGB贴图-sRGB

储存数据

非导体（电介质）diffuse color/Reflectance color（Diffuse Reflected Color/Albedo）and specular reflection of metal conductorsF0值;
非导体使用4%的F0反射值;
混合材质（That is, a mixed material of non-conductor and metal conductor）It can be considered that two kinds of data are stored at the same time;

数据范围

原则上说,base colorLighting information is not stored in ,So there are scope constraints on the stored data.

非导体： 暗色值,尽量不要低于30-50sRGB,It should not be lower than under strict control50sRGB.对于亮色值,The map should not be higher than 240sRGB.

导体：金属一般会有70-100%的镜面反射,映射到sRGB大概为180-255, 如左图所示.

在Substance Designer软件中,你可以通过PBR BaseColor / Metallic Validatenode to verify that it is within the appropriate range.

Compare traditional workflows and Metallic：
现在的base colorDoes not contain light and shadow information;

例外：

过于微小,不适合储存在AOLighting information in ,micro-occlusion,可以叠加在basecolorAdd details in.But this part of the data is the same asaoThe light and shadow information in the data is different,Not only affects diffuse reflections,Also affects the specular part.

base color要点

1. Diffuse information for non-metallic materials,For metal materials, it is its specular reflectionF0值;
2. Base ColorExcept for micro-shading information（Micro-occlusion）以外,Should not contain any lighting information;
3. The dark value is not lower than under loose conditions30sRGB,Strictly not less than50sRGB;
4. Brightness value should not be higher240sRGB值;
5. The reflectance values ​​of pristine metals are generally very high,大概能达到70-100%的镜面反射,映射到sRGB范围大概是180-255.

Metallic贴图 Grayscale map-Linear

储存数据

The metalness of the corresponding area.A mask that acts like a coating,Tell the shader how to interpret itBase Color贴图中的RGB数据.0.0Pure black represents non-metals,1.0Pure white represents pure metal.

For example, the use of different metal degrees to express the degree of metal corrosion.

metallicTexture points

1. 金属被氧化、腐蚀、上漆、覆尘后,These areas need to be considered large as non-conductive materials.
2. 在Metall贴图中,Pure black represents non-metals,Pure white represents metal,We can use transition grayscales to represent different degrees of oxidation and dirt.
3. 如果MetallicThere are values ​​in the map below235sRGB,那么在BaseColor中对应区域的反射值也应该降低.

Roughness贴图 Grayscale map-Linear

储存数据

The smoothness of the corresponding area,irregularity.纯黑（0,0）Represents a smooth surface,纯白（1,0）代表了粗糙表面.

2.7.4 Specular/ Glossiness特有贴图

Diffuse RGB贴图-sRGB

1. DiffuseThe color in the map represents the diffuse color,原始金属由于没有漫反射,The color should be solid black（0.0）.
2. DiffuseTextures except for micro occlusion（Micro-occlusion）There should be no other lighting information outside.
3. 除了表示金属的纯黑（0,0）外,The dark value should not be lower than at most30sRGB,严格50sRGB.
4. Brightness value should not be higher240sRGB.

Specular RGB贴图-sRGB

储存数据：F0（0度菲涅尔反射值）
F0Values ​​are based on real world measurements,when not needed,Try not to use unconventional values.Strictly one should check the table.Don't forget the linear space sumsRGB的转化.

Glossiness Grayscale map-Linear

Glossiness Map A map used to describe surface unevenness,Surface irregularities can cause scattering of light.
in this sticker,纯黑（0.0）Represents roughness,纯白（1.0）Represents a smooth surface.这和M/RThe exact opposite is true for roughness maps in the workflow,But there are similar drafting principles on the design side.

2.7.5 总结

2.7.6 流程转换

对应关系：

Metallic流程到Specular流程

Base color + Metallic -> Diffuse

方法：去掉base colorof metals and mixed materialsF0数据
操作：

1. 打开base color 和 metallic,RGB模式
2. 新建diffuse图层,Pure black fill
3. 单独显示metallic,in the same speciesctrl+Left click to select any channel,选中选区.
4. Diffuse图层添加蒙版,Automatically paste the selection into the mask.
5. Does not change the layer type
6. 完成

Base color + Metallic -> Specular

方法：去掉base colorDiffuse data in ,Plus non-conductor and mixed materialsF0（默认0.04）
操作：

1. 打开base color 和 metallic,RGB模式
2. 新建Specular图层,填充#383838（0.04对应22corresponding to the gray value of 56的RGB,对应代码#383838）
3. 选中metallic,ctrl + i反向.单独显示,在通道里ctrl+Left click to select any channel,选中选区.
4. Spe图层添加蒙版,Automatically paste the selection into the mask.
5. 完成

Roughness -> Glossiness

方法：反向
操作：ctrl+i,反向

Specular流程到Metallic流程

Specular + Diffuse -> Base color + Metallic

方法：First find the data corresponding to the metal area,The properties of metals areF0在0.7-1之间,Non-metals generally do not exceed0.04,Gems can reach the highest0.17,差异明显.其次,金属没有漫反射,DiffuseMedium is black.所以我们可以从Specular或Diffusegenerated in the textureMetallic贴图.You may need to try several times to get a more consistent result than before the conversion.
操作：

1. Specular,菜单选择,色彩范围,选择阴影,Grayscale preview,调整参数.（也可以使用Diffuse图层）（If the effect is not good, you can transpose the shadow to sample the color,choose pure black,调整容差）shift+ctrl+i反选,创建蒙版;
2. alt+Left-click and drag the mask toDiffuse图层,选择蒙版,ctrl+i反向;
3. Base color完成;
4. 新建Metallic图层,填充黑色,ctrl+左键点击SpecularMask for selection,填充白色;
5. Metallic完成.

Glossiness -> Roughness

方法：反向
操作：ctrl+i,反向