Optical engineer here. This is what they don't tell you about continuous/transition/progressive bifocals: optically they don't work. The lens design is an overconstrained optimization problem and the solutions they come up with end up compromising a lot on everything, to the point that it is practically useless.
I got my first set of progressive lenses in safety glasses earlier this year as a way to try them out. Based on that experience, I switched my daily glasses to progressives in May and love them.
Once or twice a day, I notice a visual artifact that I perceive to be in my left peripheral vision, and of course I sometimes need to move my head slightly to see something, but being able to see clearly at all distances with relative ease is the exact opposite of “practically useless” IMO.
> This is what they don't tell you about continuous/transition/progressive bifocals: optically they don't work.
I'll defer to your judgement re optical properties, but I want to offer a counter-anecdote about practicality.
I've had myopia and have been wearing negative diopter glasses for over half my life. I've never needed vision correction for reading. This is not an unusual combination, and if you want a celebrity example, watch some old Apple keynote videos with the late Steve Jobs, who would repeatedly lift his glasses to read something on the phone in his hand. This "works", but can be inconvenient in some situations.
A while ago, I started thinking about progressive bifocals. Cursory web searches told me that my particular combo was impractical. My optician didn't see a problem, so I decided to trust him and got a pair made. The TLDR is that they work for me much better than the old ones. There was a period of adaptation. Going downstairs and looking at the floor/ground were a bit disorienting for a while, but i don't notice it any more. Switching between the monitor and the phone or paper in front of me works, which is why I wanted the bifocals in the first place. I only use the old glasses for watching TV, probably meaning that my TV-watching posture sucks, but fortunately I don't watch a lot of TV. I still take off the glasses for sustained book reading.
What's your lay of the land when it comes to different glass qualities and glass thickness options? Stores here (nordics) have around 4 different glass qualities for progressives, with varying and opaque names like "better" and "supreme". Thickness starts with 1.6 but store people push for 1.67 or 1.74.
I get strong upselling vibes, but hard to say. (Is the "supreme plus" noticeably better than "supreme" or merely there for upsell anchoring effect, to make people pick "supreme" without feeling they overspent?)
Are there high quality information resources for consumers on what the underlying lens material and processing technologies are?
Search HN for "ABBE". The very cheapest material has the highest optical quality. Thinner ones are for weight, which matters if you have strong prescriptions. Weight can also be countered with a smaller frame height/width, which might require a vintage or designer frame, but that's a one time cost that can used with cheaper and higher optical quality lens replacements.
Search for "Chemistrie" magnetic lens attachment in +0.5 increments. They can even stack for different focal lengths, e.g. reading vs computer screen at 36". Magnets embed in primary glasses. Expensive via local opticians, they will retrofit via mail order and buychemistrie dot com.
Aren't the bifocals just a convenience over quality? It's inconvenient to wear two sets of glasses, but why would one wear bifocals while driving? This convenience can come at a high price!
Bifocals in general are quite useful. It's nice to be able to see the road and the speedometer using the same lenses.
Traditional bifocals and progressives are different beasts. The hard outline on traditional bifocals means you get essentially two different lenses, both able to function as intended. The soft blend on progressives means you get essentially one big blurry lens that does not have well defined properties anywhere.
> The soft blend on progressives means you get essentially one big blurry lens that does not have well defined properties anywhere.
That seems to be exactly my experience with them, stated very succinctly. I've had these about 9 months and I'm still struggling with the ergonomics daily. I think I made the wrong choice.
The human brain mostly adapts. Big Optical makes $$$$ billions. A small percentage of human brains have persistent dizziness and depth perception errors, which can lead to physical injury and reduced quality of life. We don't have yet have a test funded by disablity insurance, which can determine which brains might fail to adapt.
The good news is that multiple glasses have never been cheaper or more accessible, so progressives are entirely a choice.
Yes, the core supports exact rationals. This is easier to deal with in formal verification than floating point.
I made the UI snap to a fixed precision, such that its easy to reproduce special cases with overlapping edges, coinciding vertices etc. that make up much of the complexity of the algorithm.
In a past life i tried to implement Delaunay triangulation in floating point for data that can come in a rotated square grid. Normal precision doesn't work in that case. I learned a lot about arbitrary precision numbers doing that. The question about floats here gave me flashbacks.
I am eager for a lean equivalent of flocq in rocq. When I did some lean verification of numerical algorithms I did the same thing with rationals or the reals from mathlib. The big gap between that and the actual code is the lack of a solid theory library to pull in that would give me IEEE floats that is at the same level of quality as Flocq. I’m eager for that to come along (unless it has and I just haven’t found it yet).
I think to do efficient formally verified geometry with floating point we would also need something like Shewchuk robust predicates. (I worked with them in the past to write robust software that is not formally verified. Did not read up, if there is a formally verified library for them.) Shewchuk robust predicates give certain consistency guarantees that are nice to have when implementing computational geometry with floating points and I think can be formalized.
Add to that that they are (at least perceived to be) supporting AI, which the majority of people do not want, and data centers are physical faceless embodiments of big tech corporations, which people are increasingly against.
I strive for a “simple” lifestyle not because I believe it will be enjoyable. Quite the opposite. A simple lifestyle is much more laborious, arduous, and mentally taxing in terms of all the minutiae I need to worry about to achieve even modest levels of comfort. E.g. Do I have enough wood stored for the winter?
I strive for a simple life because it gives meaning to life, and a connection to the earth and other living things. It keeps me resilient in the face of hardship and less reliant on other people. It also provides a connection to the past and our heritage.
Because I don't want to deal with a hundred of anything, and I don't want to deal with decimal points. I want everything I measure to be near single digit numbers. Hence, inches for common dimensions like a "2x4". I can handle something being 5 1/4 inches. How the hell large is 133 mm? Humans are not good at intuiting numbers far from unity.
Miles are great. The typical highway speed limit is about a mile a minute. You can easily lower bound how long it will take to get somewhere if you know how far it is in miles.
In cooking, I often need to halve quantities in recipes, hence pounds and ounces. Watching cooking channels give metric quantities is absolutely baffling to me. You see things like 175 mL. That is 2 sigfigs too many.
Yes. I see the 6 and I think: pretty tall, just a bit taller than me as a baseline. Then the 3 indicates another bit more. At no point am I adding the quantities to achieve a total. It’s two pieces of information in something akin to a binary search.
I do woodworking and framing and approach is similar. Measure out to 6 feet first, then move out 3 inches more. It’s iterative refinement. To measure lengths I always do a few bisections like 3 feet, 2 inches, and 3/4 plus a sixteenth. I can remember a sequence of 3 or 4 integers for about a minute, long enough to transfer the measurement. Give me something like 135mm, and I’ll forget in a few seconds.
Don’t take up baking then, where the difference between 175 mLs of water and 200 mLs of water can be the difference between unworkable dough and the perfect pie crust.
This is really neat, and I think I can use it in some of my projects as a simple front end to physical simulation tools. One question I have: do you have true 3D bindings? I see there is ImPlot3D, but right now I need to render meshes in OpenGL (or WebGL as the case will be). Is there a way for me to define shaders and feed it triangle soup?
And anyone implementing numerical algorithms is thankful for the tremendous amount of thought put into the fp spec. The complexity is worth it and makes the code much safer.
There was actually no "thought" being put into the IEEE spec as such. It was merely a codification of the design of the Intel FPU (only one of many, very different implementations of FP units pre-standardisation). There was thought put into that implementation, but the "standard" is merely a codification of that design.
It has many many warts, and many design choices were made given the constraints of hardware of that time, not by considerations in terms of a standard.
imo they were wrong almost as much as they were right. -0.0, the plethora of NaNs, and having separate Inf and NaN all make the life of people writing algorithms a lot more annoying for very little benefit.
Perhaps the solution is to rethink the role of the fridge in the kitchen. It could be designed to be a part of a kitchen island, or have cabinets placed above it. In conventional kitchens, a chest does not make sense. But it could be well integrated if we start with the assumptions the fridge will be a chest.
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