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Well, the rendering is not really "physics based". This would imply some sort of first-principles formulation, and you see those only in some renderers. Render
by fsloth 6y ago
Well, the rendering is not really "physics based". This would imply some sort of first-principles formulation, and you see those only in some renderers.
Rendering algorithms are more like an artistic bag of tricks. The "physically based" implies the tricks are approximating the visual acuity of realistic scenes with physics inspired approximations and the like.
- q3k 6y agoPBR algorithms tend to at least start from the rendering equation and simplify/approximate from that. They attempt to maintain some semblance of accuracy by eg. employing the conservation of energy of emitted vs. received light of every point of the scene; or expressing matte texture by the statistical behaviour microfacets of a rough surface; or using actual radiometry/photometry units to express lighting elements of the scene; making the scene also be expressed in concrete real-world units, ... There's still a lot of cheating and smoke and mirrors, but at least all these operate from the idea that the math should check out. This is in contrast to more oldschool approaches that were fully dependent on tweaking things until they looked right - ie., taking blinn-phong in a scene with some 'ambient lighting' and operating in fully imaginary units, modified by an artist on scene-by-scene basis.