Make Your Renders Unnecessarily Complicated by Modeling a Film Camera in Blender [video]

The physics of light is relatively simple. Blender wants to look photorealistic, so cycles (a branched path tracer, commonly known as a ray tracer) almost perfectly models how light works. That means these emergent properties just work.

It wouldn't work under a rasteriser (Blender has one, called Eevee) as those operate using a complex series of approximations of reality that are more difficult to create but run far faster. But because Cycles (slower, but more realistic) operates by mimicking how light works this kind of thing is entirely possible.

Well, that's the best part of it: the underlying physics model is really easy!

A pinhole camera requires zero additional physics, just a simulation of light rays passing through a small hole. A lens just requires Snell's Law - which is pretty much trivial. Adding dispersion is just a matter of using a formula instead of a constant for the refractive index of the lens, and doing the raytracing using random wavelengths instead of a single "composite" one.

Raytracers capable of doing this are implemented in a few hundred lines of code as a toy project. The difficult part is getting it to render quickly - and of course modeling the scene properly.

raytracing rendering moved to physics based rendering a while ago: the core idea is to approximate the physics of light as accurately as can reasonably be made fast. It's not like it's solving a wave equation directly, it's using a statistical sampling of a model of how light interacts with different interfaces between mediums. This is basically the easiest way to get photorealistic renders: the human brain is very good at noticing when your scene has non-physical lighting (not in a 'ahah, the specular highlights violate conservation of energy' way, but in a 'this looks fake' way).

(this approach was started by some researchers who basically said 'well, let's make a simple scene for real and measure everything and make our render look identical' https://en.wikipedia.org/wiki/Cornell_box )

I'd also (re-)add: film is just one part of a transmission process.

Film has to be developed into something. And that's a chemical process, which is non-linear. Developer, the bath you put film in to activate the still blank but exposed reel, to turn the grains into actual "developed" photo, is a complex and local analog process. "Developer" is expended while developing film & becomes less effective at developing, creating a much stronger local contrast across pictures in a natural chemical way.

There's a pretty complex Shannon Information Theory system going on here, which I'm not certain how to model. There's maybe a information->transmit->medium->receive->information model between the scene and the film. Then an entirely separate information->transmit->medium->recieve->information model between the undeveloped scene and what actually shows up when you "develop" the film.

As you say, there are quite a variety of film types with different behaviors. https://github.com/t3mujin/t3mujinpack is set of Darktable presets to emulate various types of film. But the behavior of the film is still only half of the process. As I said in my previous post, developing the film is a complex chemical process, with lots of local effects for different parts of the image. There's enormous power here. https://filmulator.org/ is an epic project, that, in my view, is incredibly applicable to almost all modern digital photography, that could help us so much, to move beyond raw data & help us appreciate scenes more naturally. It's not "correct" but my personal view is the aesthetic is much better, and it somewhat represents what the human eye does anyways, with it's incredible ability to comprehend & view dynamic range.

> True, but film is more than just three color planes.

Yes, which is why I said it was the part about having three planes to gracefully point you towards what you Could you watch the content we are trying to discuss here? I know it’s HN tradition to comment without reading but it doesn’t really help.

I think this is reasonable. If nothing else, it is the aspect least possible to imitate. If included, the best imitation would be cheap strobing. Anything better than that would require synthesis, which is something that even rendering engines require significant sacrifices to produce.