i know ink & switch gets a lot of play here. this video has it all: a really cool app, a discussion of interface philosophy and decisions, and engineering roadblocks at the edge of performance (plus a Q&A i haven’t finished)

requiring the pencil for your app to work relegates the product to niche status. I remember products requiring a Light Pen, boy was that lousy technology. Software that requires hardware narrows your audience terribly. It also prevents people from trying it out on a 30 day trial, because they don't own the pre-requisite hardware. History has not been kind to software with this requirement. The Wacom tablets are used by most of the artists I know, because they have a tilt sensing in the pen, and it has really high precision. The Apple pencil is different technology than Wacom, and doesn't have tilt compensation. But it is pretty good, and much cheaper than the Wacom. Apple has the ability to bump the refresh rate up on their iPad Pro tablets, an obscure feature that few realize exists. So far, nobody has beaten the Wacom Cintiq system for overall artistic feel. There is also the friction coefficient, which Wacom cares about. Apple has a glossy surface which doesn't "bite" well. An artist's time is very valuable, and having the best equipment is cheap in the larger scheme of things.

procreate is a counterpoint to that idea from this very day

I have revised the term.

FWIW, regarding friction, I have the iPad Pro with a Paperlike 2 screen protector, and it is easily the closest thing to paper I've ever used. I mostly use iPad for notes these days (along with the 'Concepts' app with an infinite canvas).

Ever since the iPad lowered its price dramatically (often during holiday times, dropping below $300), Apple has crushed the Android competition, and with its incredible software store is a formidable computing platform, now actually a larger installed base than their desktop computers. I can see the real reason for ARM on the MacBooks is that they want to have the same software available, because the Mac OS has stagnated, and as a percentage of total computing is dropping fast. I sure didn't like it when Apple orphaned the iPad 2 and 3, turned my pristine devices into paperweights. But that's Apple for you; fairly ruthless about backwards compatibility.

engineering roadblocks at the edge of performance

I can't help but get the impression that she isn't aware of the years of research in 3D game engine design. She is basically re-discovering scene graph optimization techniques like LOD rendering and spatial B-tree optimizations that game engines have been using for years. Techniques like offloading tasks onto another thread that may cause you to miss hard real time deadlines is how game engine physics and game AI have been implemented for years. It's weird because she mentions taking the idea of a frame rate counter from graphics programming, but then seems to ignore everything else from graphics programming? Definitely a cool app from a UI / UX research perspective though 🙂

she lists that as an area of obvious future research during the Q&A—there are many tradeoffs for building a consumer app in a game engine rather than using native components etc. especially from a rapid-prototyping perspective (as well as using inputs like the apple pencil)

Fair enough. I didn't get to the Q&A yet. I don't know much about iOS either. I get starting from the native components for a prototype, but she obviously very quickly got the point where she outgrew the native framework, and continued fighting against the grain. I have the intuition that she spent just as much if not more work by trying to stay with the native frameworks. I would have bailed much sooner in process and just used a game engine. She admits that she ended up having to re-implement much of the rendering components anyway.