Mikhail Kyyashko "PBR (physically based rendering) for artists and programmers"

GameDev Tech

1. Roman Tinkov PBR for artists and programmers

2. Graphics evolution Far Cry 3 Far Cry  5

3. Physically based rendering (PBR) – collection of render techniques aimed to mimic light behavior in a physically plausible way. Uses optics principles and physical properties of surfaces Physically based , not physically correct rendering. Uses real world physics approximation To be considered physically based must follow next conditions: - Be based on the microfacet surface model - Be energy conserving - Use a physically based BRDF

4. Microfacet theory Any surface at a microscopic scale can be described by tiny little perfectly reflective mirrors Rough surface scatter incoming light in various directions

5. Energy conservation Outgoing light energy should never exceed the incoming light energy (excluding emissive surfaces) More rough surface = specular reflection area increases, brightness decreases

6. Bidirectional reflectance distribution function (BRDF) Describes the reflectance properties of a surface Many different BRDF models – some of which are not physically plausible

7. Practical use of PBR Two common workflows: Metal – Roughness Specular - Glossiness Based on physical properties: Albedo Gloss Reflectivity

8. Metal – roughness Two main types of surfaces: Conductive (Metals) Non – conductive (Dielectrics)

9. Physical nature of materials Some parameters can be obtained from real world. Initially by using photogrammetery . Can be found on Internet Some editors has material preset with these values.

10. Photogrammetery Technique  used to obtain information from real world using photography After processing provides 3D model with texture information De- lighted textures = Albedo  Surface smoothness measured by Glossmeter

11. Shaders Program that handles graphical calculations Takes texture maps as inputs PBR shaders are quite heavy Less guessing in search of correct value

12. Visual shader editors Non – programmers can create own shaders Based on template shader written by programmers Examples: Unreal material editor, Amplify shader editor for Unity, Blender material editor

13. Summary PBR is an approximation of real world, still have good benefits: Image look better, close to real world Artists can use real physical values in material creation, less guessings and hacks Programmers can rely more on mathematical functions than on visual guidance Most important! PBR material will look correctly in any lighting conditions Sketchfab PBR sphere

14. THANK YOU!

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