PBR Metallic/Roughness工作流中Albedo与F0的计算方法 | 您所在的位置:网站首页 › spec贴图 › PBR Metallic/Roughness工作流中Albedo与F0的计算方法 |
首先简单回顾一下典型的纯金属与绝缘体的PBR属性: 纯金属: Albedo(diff): 0 F0(spec): >0.3 (or 0.5, epic/allegorithmic etc.) Metallic: 1 绝缘体: Albedo(diff):可为0-1 F0(spec):0-0.08 (allegorithmic etc.), 典型值0.04 Metallic: 0已知某材质的BaseColor、Metallic、SpecularScale(默认值0.5),欲求其diff(albedo)与spec(F0),可用如下公式: half DielectricSpecular = 0.08 * SpecularScale; half3 DiffuseColor = BaseColor * (1 - Metallic); half3 SpecularColor = DielectricSpecular * (1 - Metallic) + BaseColor * Metallic;可以看出: 对于纯金属而言: Metallic=1 DiffuseColor=0 SpecularColor = BaseColor 对于绝缘体而言: Metallic=0 DiffuseColor = BaseColor SpecularColor = DielectricSpecular = 0.08 * SpecularScale(默认0.5)= 0.04(默认) 对于介于两者之间的半导体而言: Metallic=(0,1) DiffuseColor = BaseColor * (1 - Metallic) SpecularColor = DielectricSpecular * (1 - Metallic) + BaseColor * Metallic = 0.08 * SpecularScale * (1 - Metallic) + BaseColor * Metallic由此可见: 对于一张贴图而言,因为SpecularScale是统一指定的,所以对于其贴图中的绝缘体而言,其F0是统一的 对于一般的半导体metallic情况,其spec为DielectricSpecular、BaseColor二者的lerp,但注意,其实F0位于0.08-0.3(or 0.5)之间的情况很少;而其diff则可用basecolor与(1-metallic)简单计算出来 考虑一般的半导体metallic情况,DiffuseColor + SpecularColor=(BaseColor + DielectricSpecular) * (1 - Metallic) + BaseColor * Metallic,其中DielectricSpecular的最大值为0.08,而BaseColor、Metallic均位于(0,1),但BaseColor=1、DielectricSpecular=0.08且Metallic=0时,整个式子最大值为1.08,基本能量守恒 |
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