zlsa's recent activity

  1. Comment on Kerbal Space Program 2 Cinematic Announce Trailer in ~games

    zlsa Link Parent
    And that is an inherent flaw, caused by Unity's choice of C#. It might not impact a simple game as much, but it's still a design decision they made that makes Unity objectively worse at...

    And that is an inherent flaw, caused by Unity's choice of C#. It might not impact a simple game as much, but it's still a design decision they made that makes Unity objectively worse at performance compared to other game engines.

    2 votes
  2. Comment on Kerbal Space Program 2 Cinematic Announce Trailer in ~games

    zlsa Link Parent
    True, but the original quote was that there was nothing inherently wrong with Unity, which I disputed. (I still personally use Unity, because UE4 is so difficult to get started with, especially on...

    True, but the original quote was that there was nothing inherently wrong with Unity, which I disputed. (I still personally use Unity, because UE4 is so difficult to get started with, especially on Linux.)

    3 votes
  3. Comment on Kerbal Space Program 2 Cinematic Announce Trailer in ~games

    zlsa Link Parent
    Yes, there is. Unity uses C#, a garbage-collected language, in a scenario requiring high performance. The same code written in C# will be slower than C++ almost every time. Worse, garbage...

    There's nothing inherently wrong with unity.

    Yes, there is. Unity uses C#, a garbage-collected language, in a scenario requiring high performance. The same code written in C# will be slower than C++ almost every time. Worse, garbage collection isn't always predictable, leading to frame drops and stuttering. Here's a short article by the developers of Cuphead, on how to optimize a Unity game for the Nintendo Switch. Their advice on how to improve garbage collection performance is telling:

    Luckily, we had the RAM budget to increase the heap so that it collected once every 15-20 minutes. Given we also trigger garbage collection on every pause, load, or restart (when invisible to the player) and because, well, Cuphead is a very difficult game, it is extraordinarily unlikely that players will be in a level long enough to experience garbage collection during gameplay.

    Essentially, they simply delay garbage collection until a loading screen is shown. Working around inherent engine issues like this should not be a normal part of optimization for a game.

    4 votes
  4. Comment on The Valve Index Ear Speakers - Research, design, and evolution in ~tech

    zlsa Link
    I feel that one of Valve's primary goals was to anchor themselves in the high-end VR space, as opposed to the mid-low end of Oculus/WMR hardware. Audio contributes hugely to presence, and Oculus...

    I feel that one of Valve's primary goals was to anchor themselves in the high-end VR space, as opposed to the mid-low end of Oculus/WMR hardware. Audio contributes hugely to presence, and Oculus in particular has decided to go with decidedly sub-par speakers with their Rift S and Quest.

    Instead of on-ear headphones (like the Rift CV1) or Valve's over-ear speakers (in the article), the Quest and Rift S have gone with an awkward hole in the structure that just kind of lets sound out. I've used a similar system on the Oculus Go (where it's not as big a drawback, being a $200 media machine), and it just doesn't sound good at all. Oculus has supposedly improved the speaker quality on the Quest, but at the end of the day, you're just shooting sound down a plastic tube at the user's ear.

    (The other obvious indicator of Valve's commitment to high-end VR hardware is the IPD slider, which is present on the Oculus Quest but not the Oculus Rift S or any WMR headset, AFAIK.)

    3 votes
  5. Comment on SpaceX's Starship prototype aces first untethered hop test in ~tech

    zlsa Link
    This is the first flight of SpaceX's Starship prototype, known as Starhopper. Starhopper is powered by a single SpaceX Raptor engine. The Raptor engine is a powerful full-flow staged combustion...

    This is the first flight of SpaceX's Starship prototype, known as Starhopper. Starhopper is powered by a single SpaceX Raptor engine. The Raptor engine is a powerful full-flow staged combustion engine, which improves efficiency and performance at the cost of complexity.


    Drone view of the flight: https://twitter.com/elonmusk/status/1154674872041103360
    Engine view of the flight: https://twitter.com/elonmusk/status/1154629726914220032

    Why this is important

    Essentially, rocket engines need pumps to pump fuel into the combustion chamber itself. Most engines today [1] are powered by turbopumps, where the pumps (one each for the fuel and oxidizer) are powered by a gas turbine, running off the same two fuels. The resulting exhaust from the gas turbine is dumped overboard (very prominently visible in this photo of a SpaceX Merlin 1D engine test.)

    However, dumping the exhaust overboard reduces efficiency. The gas turbine is typically run fuel-rich to keep temperatures down (basically using some extra unburnt fuel to carry the heat away.) This means a fraction of the fuel is essentially wasted and does not contribute to the thrust of the engine.

    The Space Shuttle Main Engines (aka SSME, aka RS-25) were staged combustion cycle engines. In a staged combustion cycle engine, the two propellants are combined in a preburner, and the resulting high-pressure fuel-rich exhaust is routed through the turbine and then to the main combustion chamber. The remaining fuel in the preburner exhaust is burnt in the combustion chamber, which increases efficiency (and performance) compared to gas-generator engines.

    Full-flow staged combustion is even more complex. Rather than the one shared turbopump shaft of gas-generator or staged combustion cycle engines, FFSC engines have two turbines, each one running its own pump (one for fuel, one for oxidizer.) There are two preburners, one running fuel-rich and the other running oxidizer-rich. Unlike a normal staged combustion engine, which must still feed fuel and oxidizer directly into the combustion chamber alongside the preburner exhaust, FFSC engines run all of the fuel and oxidizer through the turbines. This improves performance in a number of ways:

    1. Because the preburners have such an extreme ratio of fuel to oxidizer (and therefore much more mass flow than other engine types), the remaining unburnt propellant helps keep the turbine much cooler, improving engine lifetime.
    2. Because the propellant all goes through the preburner (and is heated up by the combustion within the preburner), much of the propellant is gaseous, not liquid. This improves combustion efficiency in the combustion chamber. (This gasification of propellants to improve combustion efficiency is exactly what fuel injectors do for the engine in your car[2].)
    3. Unlike gas generator or normal staged combustion engines, FFSC engines don't need to have a single shaft for the turbine (very very hot), the oxygen (very very cold, making metals extremely brittle), and the fuel (which cannot come into contact with the oxidizer at the risk of engine-rich combustion [3].) This keeps the disparate fluids separate, simplifying the materials chosen for the turbine shaft, housing, and any seals.

    The primary downside of FFSC engines are the inordinate engineering complexity compared to gas generator or even staged combustion engines[4]. There's also the careful management of two turbines: now, you have two turbines and pumps to keep track of, and the fuel to oxidizer ratio must be carefully maintained by controlling the ratio of propellant sent to the preburners.


    Now, back to Starhopper. It's basically a flying water tank (no seriously, the thing was built by Caldwell Water Tanks.) Starhopper is a shortened prototype of the future Starship[5], which will have longer fuel tanks and an area at the nose for cargo and crew.

    If you've ever seen close-up photos of Starhopper, you'll have noticed that there's not much flattering to say about its construction. But smooth surfaces and sealed pipes aren't necessary if you're just flying a a couple of kilometers and staying well below Mach 1. Starhopper's primary purpose is to test the Raptor engine in-flight, with all the moving and shaking that entails. It also gives SpaceX a great test article for trying out new ground-side equipment, procedures, and other aspects not strictly related to the vehicle itself.

    At the same time, SpaceX is building the structure for the first full-scale prototypes in Florida and Texas. Elon's (wildly optimistic) timeline for these is first flights in 2-3 months, then reaching Earth orbit in another 2-3 months (presumably with just the single stage, which would also be a new first if they pull it off.) That said, don't expect it to happen that quickly. I'd be surprised if either of them hits 10 kilometers altitude by the end of this year.


    [1]: Rocket Lab's Rutherford engine is a notable exception with its battery-powered fuel pump.

    [2]: Yes, you drive an EV. I'm not talking about your car.

    [3]: When engine parts begin to enter the turbine. This is not a good thing, and will typically result in complete destruction of your rocket engine.

    [4]: Yes, the Raptor engine in the photo probably has a lot of development sensors on it.

    [5]: Source: https://twitter.com/elonmusk/status/1122829331401601029

    12 votes
  6. Comment on How do you handle your different online identities versus your real life identity? in ~talk

    zlsa Link
    This is something I've had problems with as well. I have a (relatively populated) GitHub profile, a website for my online identity, projects with my online pseudonym... but when I've done contract...

    This is something I've had problems with as well. I have a (relatively populated) GitHub profile, a website for my online identity, projects with my online pseudonym... but when I've done contract work, there's always that awkward moment when I say "oh yeah, make those checks to <real name>." I started all of this because I wanted to avoid using my real name online (and still do). I even have a Gmail account as my pseudonym, which I use for most of my online non-finance activities. My pseudonym and real-life identity are so disconnected that it should be virtually impossible for a normal person to connect the two.

    That said, I'm considering transitioning my online presence to my real name. It's much more unique (which is why I started using a pseudonym in the first place), so people will be able to google my name and get results unique to me. But there are always crazies, and I don't want them to find out my real name or (god forbid) my home address. I know of somebody who was accused of plagiarism in their online work, and the accuser had sent the "proof" to their real-life employer, in the hope of getting them kicked out.

    So while I do want to improve my online presence, it's a one-way operation. So I'm holding off for now.

    6 votes
  7. Comment on SpaceX - Initial results from investigation into Crew Dragon explosion during engine tests on April 20, 2019 in ~tech

    zlsa Link Parent
    This was (as far as we know) the second-to-last SuperDraco test firing before crew. If the capsule had not exploded, it would have been used for the in-flight abort test, where they try to...

    This was (as far as we know) the second-to-last SuperDraco test firing before crew. If the capsule had not exploded, it would have been used for the in-flight abort test, where they try to activate the launch abort system while in-flight.

    2 votes
  8. Comment on Epic Games supports Blender Foundation with $1.2 million Epic MegaGrant in ~tech

    zlsa Link Parent
    There are lots and lots of changes. Personally, for anyone just starting out, I would strongly recommend using 2.80 right now. 2.79 will be the legacy option in just a few weeks, and while you can...

    There are lots and lots of changes. Personally, for anyone just starting out, I would strongly recommend using 2.80 right now. 2.79 will be the legacy option in just a few weeks, and while you can transition from 2.79 to 2.80 without too much fuss, why not start learning it now?

    (In the past, 2.80 was super unstable, but it's rock-solid for me now. As always, YMMV.)

    7 votes
  9. Comment on Epic Games supports Blender Foundation with $1.2 million Epic MegaGrant in ~tech

    zlsa Link
    This comes right on the heels of the announcement of the Blender 2.80 release candidate, hopefully upgrading to stable by the end of the month. I've been using Blender 2.80 for a few months now,...

    This comes right on the heels of the announcement of the Blender 2.80 release candidate, hopefully upgrading to stable by the end of the month. I've been using Blender 2.80 for a few months now, and I'm incredibly impressed with how far they've gone in such a short time.

    If you were on the fence about learning Blender due to its historically unintuitive interface, give 2.80 a try. Lots of things have changed, and it's much more approachable now.

    8 votes
  10. Comment on When posting a link that has already been posted, give the submitter the option to just bump the old topic to the top of the activity sort in ~tildes

    zlsa Link
    Would there be anything preventing somebody from posting a link, and then repeatedly bumping it with alt accounts? It would be an invisible method of keeping a post visible without affecting its...

    Would there be anything preventing somebody from posting a link, and then repeatedly bumping it with alt accounts? It would be an invisible method of keeping a post visible without affecting its comment or vote counts.

    9 votes
  11. Comment on Sony and Microsoft to explore strategic partnership, collaborate on new cloud-based solutions for gaming experiences and AI solutions in ~tech

    zlsa Link Parent
    I usually have ~50ms ping to a US West Coast. Despite having an "up to 60Mbps" plan, YouTube is usually throttled to under 4Mbps. And I live within 50 miles of the San Francisco Bay Area.

    I usually have ~50ms ping to a US West Coast. Despite having an "up to 60Mbps" plan, YouTube is usually throttled to under 4Mbps.

    And I live within 50 miles of the San Francisco Bay Area.

    2 votes
  12. Comment on What's the best advice you've been given regarding photography? in ~hobbies

    zlsa Link
    Rule of Thirds. This can make almost anything look better, and it's really really easy to do. Just imagine a tic-tac-toe board over your photo and try to put interesting things under the lines, or...
    1. Rule of Thirds. This can make almost anything look better, and it's really really easy to do. Just imagine a tic-tac-toe board over your photo and try to put interesting things under the lines, or where the lines meet.
    2. Prefer to underexpose rather than overexpose. Often, pixels that are nearly black can be brightened up again, but a pixel that's white is always going to be white. Essentially, while pure white is a value of 1, there's really no such thing as pure black in normal photography, so there's more room to recover very dark pixels. (Higher-end cameras are far better at recovering useful pictures from underexposed areas, but phone cameras aren't nearly as good. Don't rely on being able to recover underexposed photos taken on a phone.)
    3. Don't ever use the flash unless you just want to see something. Flash has many issues, especially on phones; with the flash so close to the camera, you get a weird, flat look that really doesn't ever look good. Plus, the rapid falloff means you need to be pretty close to your subject anyway. If you need to see something, then use flash; but don't use it if you don't need to.
    4. Take a lot of photos. Nobody gets home and thinks "Damn, I wish I took less photos." Most of these photos won't be any good, and that's fine. Nobody publishes their worst photos. All that matters is your best photos, and the more photos you take, the more will be good.
    11 votes
  13. Comment on Setting aside the musical content (if you can), what are the best music videos you know? in ~music

  14. Comment on Jordan Peterson Announces Free Speech Platform ‘Thinkspot’ in ~tech

    zlsa Link Parent
    Honestly, this is one of the few things votes should handle well. If people simply downvoted such a post (on platforms with downvotes, anyway), it would be hidden very quickly. Unfortunately, for...

    Honestly, this is one of the few things votes should handle well. If people simply downvoted such a post (on platforms with downvotes, anyway), it would be hidden very quickly. Unfortunately, for some reason, people seem to only downvote things they disagree with and just blanket-upvote the rest.

    4 votes
  15. Comment on Jordan Peterson Announces Free Speech Platform ‘Thinkspot’ in ~tech

    zlsa Link Parent
    I used to moderate a moderate-size subreddit, and this was absolutely true. We required AutoModerator to function. If it went down, we would have been screwed. It did so many convenient things,...

    IMO without Deimos' Automoderator reddit would have imploded ages ago

    I used to moderate a moderate-size subreddit, and this was absolutely true. We required AutoModerator to function. If it went down, we would have been screwed. It did so many convenient things, like automatically reporting potentially rule-breaking comments (the big one), automatically removing the more egregious ones, automatically flairing posts, etc.

    "Reddit's moderator tools used to suck. They still do, but they used to, too."

    15 votes
  16. Comment on Blender is Free Software in ~comp

    zlsa Link Parent
    I phrased that badly, sorry. A better phrase would have been slow acceptance. I personally use Blender almost every day, and I've been using 2.8 for the last few months now. I'm amazed at how far...

    I phrased that badly, sorry. A better phrase would have been slow acceptance.

    I personally use Blender almost every day, and I've been using 2.8 for the last few months now. I'm amazed at how far Blender has come in just the last year. Eevee is game-changing.

    Here's a demo of 2.8 and its real-time render engine Eevee.

    1 vote
  17. Comment on Blender is Free Software in ~comp

    zlsa Link
    This article provides a defense for using the GPL, instead of the recent wave of projects moving towards "source-available" licenses that often prohibit commercial use or hosting of software. The...

    This article provides a defense for using the GPL, instead of the recent wave of projects moving towards "source-available" licenses that often prohibit commercial use or hosting of software.

    The article is by Ton Roosendaal, the chairman of the Blender Foundation.


    Interestingly, Blender started out as an in-house tool, written by an animation studio (NeoGeo). After NeoGeo was acquired by another company, Ton took Blender and formed a new company, hoping to follow a free product/commercial support model. While this goal was not met, a community crowdfunding campaign was successful in transferring Blender to the newly formed Blender Foundation, which then released Blender under the GPL.

    After this, Blender has consistently seen slow and steady growth. In recent years, it's seen increasing use in commercial animation studios; notably, the feature film Next Gen was made almost entirely with Blender.

    6 votes