wareya · HackerTrans

5 เดือนที่ผ่านมาdiscuss

It's worrying, but it's consistent with how copyright law is currently written. Laws haven't caught up with what technology is currently capable of yet. The discussion should be whether, and if so how, our laws should be tweaked to stop this from getting out of hand, IMO.

wareya

5 เดือนที่ผ่านมาdiscuss

> I don't believe this, and I doubt that the sense of copying in copyright law is so literal.

It is actually that literal, really.

> For instance, if I generated the exact text of a novel by looking for hash collisions,

This is a copyright violation because you're using the original to construct the copy. It's not a pure RNG.

> or by producing random strings of letters,

This wouldn't be a copyright violation, but nobody would believe you.

> or by hammering the middle button on my phone's autosuggestion keyboard, I would still have produced a copy and I would not be safe to distribute it.

This would probably be a copyright violation.

You probably think that this is hypothetical, but problems like this do actually go to court all the time, especially in the music industry, where people try to enforce copyright on melodies that have the informational uniqueness of an eight-word sentence.

> APIs are usually not copyrightable,

This was commonly believed among developers for a long time, but it turned out to not be true.

> This does not really sound like "the opposite of correct".

The important part is that information about the implementation can absolutely be in the spec without necessarily being copyrightable (and in real world clean room RE, you end up with a LOT of implementation details). You were saying the opposite, that it was a spec of the API as opposed to a spec of the implementation.

wareya

5 เดือนที่ผ่านมาdiscuss

It sounds to me like you're responding to a different argument than they're actually making and reading intent into it that isn't written into it.

wareya

5 เดือนที่ผ่านมาdiscuss

That's the "but their case would still fail if the second author could show that their work was independent, no matter how improbable" part of the post you're responding to.

wareya

5 เดือนที่ผ่านมาdiscuss

This actually isn't what legal precedent currently says. The precedent is currently looking at actual output, not models being tainted. If you think this is morally wrong, look into getting the laws changed (serious).

wareya

5 เดือนที่ผ่านมาdiscuss

> If you had a hermetically sealed code base that just happened to coincide line for line with the codebase for GCC, it would still be a copy.

If you somehow actually randomly produce the same code without a reference, it's not a copy and doesn't violate copyright. You're going to get sued and lose, but platonically, you're in the clear. If it's merely somewhat similar, then you're probably in the clear in practice too: it gets very easy very fast to argue that the similarities are structural consequences of the uncopyrightable parts of the functionality.

> The actual meaning of a "clean room implementation" is that it is derived from an API and not from an implementation (I am simplifying slightly).

This is almost the opposite of correct. A clean room implementation's dirty phase produces a specification that is allowed to include uncopyrightable implementation details. It is NOT defined as producing an API, and if you produce an API spec that matches the original too closely, you might have just dirtied your process by including copyrightable parts of the shape of the API in the spec. Google vs Oracle made this more annoying than it used to be.

> Whether the reimplementation is actually a "new implementation" is a subjective but empirical question that basically hinges on how similar the new codebase is to the old one. If it's too similar, it's a copy.

If you follow CRRE, it's not a copy, full stop, even if it's somehow 1:1 identical. It's going to be JUDGED as a copy, because substantial similarity for nontrivial amounts of code means that you almost certainly stepped outside of the clean room process and it no longer functions as a defense, but if you did follow CRRE, then it's platonically not a copy.

> What the chardet maintainers have done here is legally very irresponsible.

I agree with this, but it's probably not as dramatic as you think it is. There was an issue with a free Japanese font/typeface a decade or two ago that was accused of mechanically (rather than manually) copying the outlines of a commercial Japanese font. Typeface outlines aren't copyrightable in the US or Japan, but they are in some parts of Europe, and the exact structure of a given font is copyrightable everywhere (e.g. the vector data or bitmap field for a digital typeface, as opposed to the idea of its shape). What was the outcome of this problem? Distros stopped shipping the font and replaced it with something vaguely compatible. Was the font actually infringing? Probably not, but better safe than sorry.

wareya

9 ปีที่แล้วdiscuss

Creole is a scientific term, not a casual one. Creoles evolve from pidgins. English was never a pidgin, and it has a very clear history. No useful interpretation of the word "creole", formally defined or not, is broad enough to actually consider English to be a creole, and no good linguist will call it one. Whoever or whatever taught you that it can be considered one, it's wrong. The people who take the Middle English creole hypothesis seriously are crackpots.

wareya

9 ปีที่แล้วdiscuss

By "continuous physics", it doesn't mean the "objects don't go through walls" thing (that's easy), it means that it actually finds the times that interactions happen. Box2d isn't able to use that in all cases, but it does allow it to act the same way as a tickless simulation if your game's physics is simple enough, like 2d platformers.

wareya

9 ปีที่แล้วdiscuss

I covered integration error in my first post here, point 3. The thing I was calling Box2D out for is the fact that it doesn't use a hacky way of rectifying collisions. It seeks out the point in time that they occur.

>It does not guarantee zero error: to do that you have to have an analytic method, which isn't applicable to a general-purpose physics simulation.

If you have constant acceleration, the analytic way to get the point you want to be at at the end of the frame is simple: just pretend your current frame is using half the added speed from the acceleration that you're going to undergo this frame. Or you could use a hermite curve or something.

wareya

9 ปีที่แล้วdiscuss

>I don't know why you keep saying this.

Because it's true. The same operation on the same data may give different results on different CPUs, even if you're operating at the machine code level (no implementation-specific optimizations).

https://randomascii.wordpress.com/2013/07/16/floating-point-...

https://randomascii.wordpress.com/2014/10/09/intel-underesti...

>Can you point me to a physics engine which gives 100% repeatable results with tickless? I'm genuinely interested, I didn't know of any that claim they achieve that, the common ones (box2d, unity and havok for example) certainly don't.

box2d is sufficiently low level that it gives programmers the tools necessary to do this.

Most notably, box2d provides the following:

>Continuous physics with time of impact solver

This directly allows developers to create a "tickless" physics simulation by breaking up the simulation into the timespans between interactions, as long as pathological situations aren't introduced (like the quake 3 ledge climbing bug). That doesn't mean that the developer will actually do so, and if the gameplay logic interacts with physics in framerate-dependent ways the result will still be wrong. It just means that the possibility is there.

Of course, this doesn't solve game logic issues with things happening only at the moment that a frame happens. That's entirely on the developer, even if they use an ideal physics engine.

At the end of this, I'll repeat that fixed timestep doesn't actually solve the problem, all it does is allow you to output higher graphical framerates than the physics simulation is running at. If the physics simulation itself can't run at full speed, you still need a way to adapt to longer frametimes, and you have to do so correctly. And if you run the physics simulation so slowly that it won't slow down on any reasonable PC, you either have a very simple game or you just added tons of input latency.

wareya

9 ปีที่แล้วdiscuss

Online games avoid that problem by having an authoritative networking architecture, not by avoiding minor deviations in CPU behavior between players. Games that use synchronized lockstep that use floating point math always desync, because floating point math differs slightly between different processors.

Curved motions are easy as long as you have simple polygons and only one of them is accelerating and is accelerating in a simple way. You remove the acceleration by skewing the polygon you're going to collide with and then you have a linear path of motion again. (if the acceleration is not constant for the duration of that frame, then skewing doesn't give the right result; as long as you have a closed form representation, though, it's entirely possible to get it right)

"Don't run on a tick-based physics engine" is a misconception. Interactions are the borders between ticks. It's just dynamic. As long as your tick doesn't contain interaction changes inside it, you can simulate that tick with 100% tickrate independence with 100% certainty.

Floating point differences between cpus are Much Larger, especially if your code uses hardware-accelerated trig at all. Games networking is authoritative for this reason.

You can get a 100% repeatable result with a tickless engine.

Fixed timestep doesn't solve the problem. If the user can't run the simulation at 60 ticks per second, they're still going to slow down, period. All you're doing is separating simulation from rendering, which basically every modern FPS under the sun already tries to do in a different way than fixed timestep does. If you run the simulation slow enough that nobody will have performance problems with it, you just added tons of input latency. Thanks a lot, sincerely, someone with dysgraphia.

wareya

9 ปีที่แล้วdiscuss

First, even at a constant framerate, different players will have different experiences with the game due to different amounts of latency in their peripherals, weird CPU bugs, very very minor floating point behavior deviations, etc. The important part of making something framerate independent is to make the effects of framerate independence /smaller enough/ than other factors that make player experiences.

It's entirely possible to not have gameplay change at different tickrates. There are three usual types of problem that cause gameplay to change at different tickrates:

1) Events that happen at specific times

If events can only happen "in sync" with ticks, then running at different framerates will make them happen at different times. Say you have a machine gun that fires once every 1/10th of a second. If you're running at 24fps, then not only do you need to make sure that you correctly output a bullet every two-or-three frames, you also have to make it so that they /act like/ they came out at a time between frames, presumably by simulating them a little extra bit or a little less depending on what's necessary to make each bullet a fixed distance apart (for example). You could also use a continuous interaction system here but that's really hardcore and doesn't matter in 99.9%+ of cases.

2) Treating curved motions as linear motions

This isn't a problem in 99% of cases, but it ~can~ be a problem. If you can't represent your physics curves in closed form, it's effectively impossible to trace them in a framerate-independent way. The only thing you can do for these things is to "fix your timestep", but "fix your timestep" should be used with extreme caution and not be applied to action games because it adds input latency and hides frame-specific-timing information from players. Recommendation: use simpler game physics. Constant acceleration everywhere you can, special-purpose closed form functions with the right curves where you can't, and avoid tight curves. This makes it less of an issue.

You might also want a collision system that allows curved paths, but if you have enough control over your game's environments, and you don't expect people to run at SUPER low framerates, this isn't an issue.

3) Running different "integral" parts of the simulation out of sync with eachother.

This isn't literally about code order execution, it's about the behavior of different pieces of code that "add up" "over time" (if you're into calculus, think antiderivatives)

If you add n to your position every frame, that's all fine and good, as long as it always starts at exactly the right time. If you add "five pixels per second" to your position, then you need to make sure that always causes the same amount of distance travelled. Quake 3 handles this by giving subframe timings to things like pressing and releasing movement keys.

Another example is gravity. Normally, game code adds a specific amount of gravity every frame, possibly adjusted for time, either before or after motion. This isn't good enough, because if you add gravity after moving, very low framerates will have a higher initial frame of gravitational movement; essentially, low framerates will skip "outside" the ideal jump arc rather than tracing it. If you add gravity before moving, the opposite happens, low framerates trace "inside" the ideal jump arc. The correct thing to do is to calculate motion with around half the added velocity from all accelerations for that frame, which basically means the average of accelerating before or after. You can also trace a hermite spline, which is more flexible (you will have perfect framerate independence for any acceleration values that only change along line segments, i.e. "constant jerk", as long as you handle start/stop conditions for changes in acceleration with a correct continuous interaction simulation), but harder to implement.

The above is only 100% ideally possible for things you can represent closed form, and in practice, people will only implement something correctly if it's not just closed form but /simple/. Many games stop short of correct jump arcs, but it's entirely possible. Gang Garrison 2 was just changed to have a correct framerate-independent jump arc.

wareya

11 ปีที่แล้วdiscuss

The whole point of robots.txt is that there are pages which people may hit that bots can't. What are you on?

wareya

11 ปีที่แล้วdiscuss

Robots.txt is different. Without it, bots have no way of knowing whether to get any other data from the site. You would need "bots allowed" information in the HTTP handshake itself to prevent bots from accidentally hitting pages they shouldn't. This can already be Very Bad.

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