PBR

• PBR(Physical based rendering) / PBS(Physical based shader)

Energy = diffuse + specular + transmission

• https://renderwonk.com/publications/

[Ndc13]Ndc 2013 김동석:UDK로 물리기반 셰이더 만들기

siggraph 2010 tri-Ace Practical Implementation of Physically-Based Shading Models at tri-Ace (Yoshiharu Gotanda) slide cource notes

siggraph 2011 Lazarov Physically Based Lighting in Call of Duty: Black Ops Dimitar Lazarov, Lead Graphics Engineer, Treyarch

Sébastien Lagarde Moving Frostbite to PBR (Sébastien Lagarde & Charles de Rousiers) https://blog.selfshadow.com/publications/s2014-shading-course/frostbite/s2014_pbs_frostbite_slides.pdf

• Etc
  • BSDF(Bidirectional Scattering Distribution Function)
  • BTDF(Bidirectional Transmission Distribution Function)
  • BSSRDF(Bidirectional Scattering Surface Reflectance Distribution Function)
  • SPDF(Scattering Probability Density Function)

Custom PBR

TODO

• https://www.slideshare.net/dongminpark71/ndc19-pbr-143928930
• 언차티드4 테크아트 파트4 Special Case Materials - Moss & Wetness & Glass
• 언차티드4 테크아트 파트3 MicroShadowBRDF Term

Ref

• https://www.slideshare.net/MRESC/pbr-vol2-131205432
• Adobe The PBR Guide
  • https://substance3d.adobe.com/tutorials/courses/the-pbr-guide-part-1
  • https://substance3d.adobe.com/tutorials/courses/the-pbr-guide-part-2

https://leegoonz.blog/2020/01/05/energy-conserved-specular-blinn-phong/ https://www.rorydriscoll.com/2009/01/25/energy-conservation-in-games/

재질

• https://dev.epicgames.com/documentation/en-us/unreal-engine/physically-based-materials-in-unreal-engine
• https://creativecloud.adobe.com/learn/substance-3d-designer/web/the-pbr-guide-part-1
• https://creativecloud.adobe.com/learn/substance-3d-designer/web/the-pbr-guide-part-2

custom

난반사(Diffuse Reflection) 정반사(Specluar Reflection)

• 방식
  • ref
    • 물리기반 머터리얼 상식
      • 직접광보다 간접광(Environment map)이 중요.
        • https://marmoset.co/shop/
          • Perpetual License $31900one-time fee (USD)
    • 디퓨즈와 스페큘러
      • How To Split Specular And Diffuse In Real Images
      • https://lifeisforu.tistory.com/382
      • https://www.virial.com/reflection-models.html
  • metal - roughness
    • base color : brdf color
    • metallic : reflectance ( specular level, Index of Refelection - 별명이 artistic metallic - 1.6)
    • roughness: glossiness를 선형화 시켜서 뒤짚은 값.
      • 사람은 대략 0.5
  • specular / glossiness
    • diffuse(albedo (알비도)) / specular / glossiness

base color/metalic / roughness 방식

• 단점
  • 텍셀 밀도가 낮을시 metalic edge 현상 발생
• base color
  • PBR Safe Color
    • https://helpx.adobe.com/substance-3d-designer/substance-compositing-graphs/nodes-reference-for-substance-compositing-graphs/node -library/material-filters/pbr-utilities/pbr-albedo-safe-color.html
    • https://helpx.adobe.com/substance-3d-designer/substance-compositing-graphs/nodes-reference-for-substance-compositing-graphs/node-library/material-filters/pbr-utilities/pbr-basecolor-metallic-validate.html
• 메탈릭
  • albedo : 밝아야함(생각보다 어둡게 나오는 경우가 많음)
  • 금속/비금속을 나누는 기준임으로 어중간한 값들의 사용은 자제해야한다.
• 거칠기 : 높을수록 정반사 비율이 낮아짐.
  • 기울여 봐야 Fresnel의 차이를 확인 할 수 있음.