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This, very much this!

I do research in a subfield of optics called nonimaging optics (optics for energy transfer, e.g. solar concentrators or lighting systems). We typically use these optical design applications, and your observations are absolutely correct. Make some optical design software that uses GPUs for raytracing, reverse-mode autodiff for optimization, sprinkle in some other modern techniques you may blow these older tools out of the water.

I am hoping to be able to get some projects going in this direction (feel free to reach out if anyone are interested).

PS: I help organize an academic conference my subfield of optics. We run a design competition this year [1,2]. Would be super cool if someone submits a design that they made by drawing inspiration from modern computer graphics tools (maybe using Mitsuba 3, by one of the authors of this book?), instead of using our classical applications in the field.

[1] https://news.ycombinator.com/item?id=42609892

[2] https://nonimaging-conference.org/competition-2025/upload/

This is one example of an area where economic incentives make it difficult to shift.

  - There aren't that many people willing to pay for such software, but those that do *really* need it, and will pay quite a bit (passing that cost on of course). 
 
  - The technical domain knowledge needed to do it properly is a barrier to many
 
  - It needs to be pretty robust

I think the main way this changes is when someone has already spend the money in an adjacent area, and realized "huh, with a little effort here we could probably eat X's lunch"

Beyond that you at most get toy systems from enthusiasts and grad students (same group?) ...

You’d be surprised! Everywhere I’ve worked, academic or industry, typically writes their own simulation software. Sometimes it’s entirely handwritten (i.e., end-to-end, preprocessing to simulation to evaluation), sometimes it’ll leverage a pre-existing open source package. I imagine this will become more and more common if, for no other reason, you can’t back-propagate an OpticStudio project and open source automatic differentiation packages are unbeatable.

I've been working on something similar, although I'm more interested in replicating the effects of existing lenses than designing new ones: https://x.com/dearlensform/status/1858229457430962318

PBRT 3rd edition actually has a great section on the topic but it's one of the parts that wasn't implemented for the GPU (by the authors, anyway): https://pbr-book.org/3ed-2018/Camera_Models/Realistic_Camera...

I once saw a youtube video of a guy who first modeled a pinhole camera in something like Blender3D and then went on to design and simulate an entire SLR camera.

I'd imagine there is fairly wide gap between having a simulation engine core and an useful engineering application

From academic side, I've found the work of Steinberg in this area extremely impressive. They are pushing the frontier to include more wave-optical phenomenon in the rendering. E.g. https://ssteinberg.xyz/2023/03/27/rtplt/

> eye-wateringly expensive

For you. Anyone doing design and manufacturing of optics will not blink at paying for software.

Well, everyone who can build this niche software is already employed to build it.

" I wonder how much work would be involved for someone to make optical design software that blows away the old tools"

Depending on use case, it already exists for gem cutters. We can simulate everything from RI to fluorescence excitation.

I predict PBR is going to fall to neural rendering. Diffusion models have been shown to learn all of the rules of optics and shaders, and they're instructable and generalizable. It's god mode for physics and is intuitive for laypersons to manipulate.

We're only at the leading edge of this, too.

It is a bit of a silly term. It was made mostly to contrast against the somewhat more adhoc methods that preceded it. The new technique was parameterized more around physical properties where the older ones were more about visual descriptions.

This paper from Disney is what kicked off the movement https://disneyanimation.com/publications/physically-based-sh...

But what alternative can you suggest which doesn’t break grammar or usage precedents like “physically based”?

Physics-based? Reality-based? Physically-derived?

It bothers me too, but I’m French. I always assumed it was some corner of the language I don’t know

I've been keeping a list of Literate Programs published as books, as well as supporting texts:

https://www.goodreads.com/review/list/21394355-william-adams...

I'd be glad to know of any I missed, or of a similar resource for websites.

The text seemed to describe it quite well. They just use a bunch of physics jargon because the book approaches rendering from the physics side of things.

Light leaving a point in a direction = light emitted from that point in that direction (zero if we aren't talking about a light bulb or something) plus all light reflected by that point in that direction.

As a mathematician by training who does a lot of programming for a living: This is the biggest misconception about math I see coming from programmers. There's frequently a complaint about notation (be it that it is too compact, too obscure, too gatekept, whatever) and the difficulty in picking out what a given "line" (meaning equation or diagram or theorem, or whatever) means without context.

Here's the thing though: Mathematics isn't code! The symbols we use to form, say, equations, are not the "code" of a paper or a proof. Unless you yourself are an expert at the domain covered by the paper, you're unlikely to be able to piece together what the paper wants to convey from the equations alone. That's because mathematics is written down by humans for humans, and is almost always conveyed as prose, and the equations (or diagrams or whatever) are merely part of that text. It is way easier to read source code for a computer program because, by definition, that is all the computer has to work with. The recipient of a mathematical text is a human with mathematical training and experience.

Don't interpret this as gatekeeping. Just as a hint that math isn't code, and is not intended to be code (barring math written as actual code for proof assistants, of course, but that's a tiny minority).

Screenshot and ask ChatGPT. Works pretty well.

There is no standard.

Filament is extremely well documented: https://google.github.io/filament/Filament.html

glTF's PBR stuff is also very well documented and aimed at realtime usage: https://www.khronos.org/gltf/pbr/

OpenPBR is a newer, much more expensive BRDF with a reference implementation written in MaterialX that iirc can compile to glsl https://academysoftwarefoundation.github.io/OpenPBR

Pick one of the BRDFs, add IBL https://bruop.github.io/ibl, and you'll get decent results for visualization applications.

I think most realtime production uses something similar to Disney BRDF when they refer to PBR.

https://media.disneyanimation.com/uploads/production/publica...

I don't think there is a standard as such that would dominate the industry. It's all approximations to give artists parameters to tweak.

IMHO - Being an ex professional CAD person I think PBR is the wrong visual style for most cad though. The main point of shading is to improve the perception of shape and part isolation there. Traditional airbrush based engineering illustration styles are much better reference. So something like Gooch with depth buffer unsharp masking IMHO would be much much more appropriate.

There's no standard and even moving things from one 3D program to another can be a painful process if someone else didn't already build in some sort of conversation.

You might find value in the glTF sample renderer https://github.com/KhronosGroup/glTF-Sample-Renderer

It won't be plug and play since you'd have to pull out the shaders and make them work in your app, but the implementation supports quite a few material variants. The PBR shader implementation starts in source/Renderer/shaders/pbr.frag

Even if you have a standard specular & diffuse model, indirect lighting is really important and you can't really just drop that into a shader.

If you want a standard I've go with OpenPBR, it is well documented and looks nice. Just skip the extra layers to begin with(fuzz/coat etc).

How would one link to a physical object?

If this is what you’re asking: there are (perhaps too discreet) links at the bottom of each page to Amazon and MIT Press to purchase the physical book.

They do, on the main site: https://www.pbrt.org

Physically Based Reading

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