PBR中的Metallic/Roughness工作流

首先回顾一下典型的纯金属与非金属的PBR属性：

• 纯金属：
  • Albedo(diff): 0
  • F0(spec): >0.3
  • Metallic: 1
• 非金属：
  • Albedo(diff)：可为非0值
  • F0(spec)：0-0.08
  • Metallic: 0

已知某Materail的BaseColor、Metallic、SpecularScale（默认值为0.5），欲求其diff与spec，则有如下公式：

half DielectricSpecular = 0.08 * SpecularScale;
half3 DiffuseColor = BaseColor * (1 - Metallic);
half3 SpecularColor = DielectricSpecular * (1 - Metallic) + BaseColor * Metallic; 

 则有：

• 对于纯金属而言：
  • DiffuseColor=0
  • SpecularColor = BaseColor
• 对于非金属而言：
  • DiffuseColor = BaseColor
  • SpecularColor = DielectricSpecular = 0.08 * SpecularScale
• 对于介于两者之间的而言：
  
  • DiffuseColor = BaseColor * (1 - Metallic)
  • SpecularColor = 0.08 * SpecularScale * (1 - Metallic) + BaseColor * Metallic