GGX really the thing?

Shrike · May 2019

So Im by no means an expert on this field
But this has been bugging me for a while

Each time I look at light sources / reflections in real life it
looks like they have a noticeably wider attenuation than GGX does, and GGX clearly still looks slightly stilized in most implementations

Image: https://us.v-cdn.net/5021068/uploads/editor/4g/spypw5nij4xf.png

(crappy photoshop)
We thought each time the most left one would be the closest we have, what are the odds the trend continues?

musashidan · May 2019

I suppose it's just the fact that fresnel ior and its effect on the GGX microfacet effect hasn't made it into the game shaders yet. The offline GGX models are FAR more realistic than Blinn/Phong.

ActionDawg · May 2019

you can choose a different tail for ggx if you like but the one most people use is a pretty good fit to life. one important thing to note is that if you're not taking multiple scattering into account any shader will lose some energy. same goes to other phenomenon, so make sure your shader definitely passes the white furnace test before changing its profile.

Farfarer · May 2019

I think GGX is mostly used because it looks fairly close to measured values while having a nicer equation than full GTR with a tail falloff other than 2.

For the moment, it's a useful standard, especially for real time usage. I don't think anyone ever thought phong was realistic, but the complexity of the equations used also increases from left to right in your image. It's about what was realistically possible using the hardware at the time.

GGX really the thing?

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