alt Hacker News> I now have a small library of simulated materials: watercolor washes, dry brush strokes, felt-tip pens, cracked glaze, pencil fills. None of them are physically accurate. I’m not simulating fluid dynamics or anything like that, I don’t need to. They’re impressions, heuristics that capture enough of the character of a material to be convincing and evoke an emotion.
I find this to be a key insight. I've been working on a black-and-white film app for a while now (it's on my website in profile if you're curious), and in the early stages I spent time poring over academic papers that claim to build an actual physical model of how silver halide emulsions react to light.
I quickly realized this was a dead end because 1) they were horribly inefficient (it's not uncommon for photographers to have 50-100MP photos these days, and I don't want my emulator to take several minutes to preview/export a full image), and 2) the result didn't even look that good/close to actual film in the end (sometimes to the point where I wondered if the authors actually looked at real film, rather than get lost into their own physical/mathematical model of how film "should behave").
Forgetting the physics for a moment, and focusing instead on what things look and feel like, and how that can be closely approximated with real time computer graphics approach, yielded far better results.
Of course the physics can sometimes shed some light on why something is missing from your results, and give you vocabulary for the mechanics of it, but that doesn't mean you should try to emulate it accurately.
I read this interview with spktra/Josh Fagin and how he worked on digitally recreating how light scatters through animation cels, which creates a certain effect that is missing from digital animation - and it was validating to read a similar insight:
"The key isn’t simulating the science perfectly, but training your eye to recognize the character of analog light through film, so you can recreate the feeling of it."
Many years ago I went to a photoshop conference to try and get better. There was a talk about converting color photos to black and white. As a former bw film photog this interested me. Black and white film is a little wierd (some people put red filters on the lenses to increase contrast)
He showed some techniques. I think someone asked a question about the best way, but the presenter got a little ranty and basically said the way that looks best to your eye is the best way.