Are there any data driven approaches to physically based rendering?

Can't we measure micro-facet depth and angle distribution of real world materials using laser speckle and use it to inform the normal distribution function? Deriving ideals from first principles is great and all, but verifying them against real world measurements seems like the bare minimum.

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corysama 19 hours ago | parent | next [-]

There have been decades of research into generalized BRDF measurement of real materials. Usually it starts with capturing calibrated images of the combination of all camera angles and all lighting angles on the hemisphere.

https://www.researchgate.net/figure/Picture-of-the-BRDF-meas...

https://www.iosb.fraunhofer.de/en/projects-and-products/sig_...

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imadr 20 hours ago | parent | prev [-]

If i’m not mistaken that’s in part how they came up with micro facet models, or at least to verify their accuracy. Take this paper for example https://www.cs.cornell.edu/~srm/publications/EGSR07-btdf.pdf

Real life measures are also useful for inverse rendering.

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kelseyfrog 19 hours ago | parent [-]

Interesting link, thank you!

It looks like a good model for lower incident angles but begins to diverse at higher angles. There's also one huge caveat - it relates the GGX model to real world ground glass. Obviously it's important to compare like to like. However, very few materials in the real world are ground glass.

Looking around my surroundings, I see painted drywall, wood, paper, plastics, and textiles. It would seemingly be a mistake to assume each of these materials behaved optically like ground glass. I hope that similar measurements are carried out on other materials.

	▲	tzumaoli 19 hours ago \| parent [-]
		The same Cornell group has done more research in this area. Here is one for capturing the microgeometry of metals https://www.cs.cornell.edu/Projects/metalappearance/ Here's another paper from a different group on capturing the microgeometry using a lot of LED lights https://svbrdf.github.io/publications/MicroLightStage/Micros... But I agree there should be a lot more work in this area!!