Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?

Comment Re:What's the point? (Score 2, Informative) 184

1. Immediate lighting rasterizer = O(S*N*L)
2. Deferred lighting rasterizter =O(S*N)+O(S*L)
3. Ray tracer = O(S*log N*L*D)

where N is the number of solid 3D elements, L is the number of direct illumination lights, D is the indirect lighting depth and S is the number of screen elements.

No matter how I look at this, ray tracing is not very compelling.

Once upon a time, we thought ray tracers were fast. If we hold screen size as a constant and set the number of bounces to 1 for a fair comparison to a 1992 era rasterizer we get the "classic" complexity analysis comparison.

1. Rasterizer = O(N*L)
2. Ray tracer = O(log N*L)

Winner: ray tracer. However, a few things have changed since 1992. First, screen size is important and should not be ignored. This is due to the increasing importance of screen space effects. Second, deferred lighting broke rasterization in half. Third, rasterizers can now do convincing shadows and fake global illumination. So, to keep up with the quality of the average 2010 rasterizer we have to set D>1. This is a 1-2-3 knockout combo for ray tracers.

Rasterizers are the current complexity king. Now, I'll tell you why it will remain the king. Ray tracers have an architecturally bad design. It looks like this:

for p in rays:
    for i in items: raytest
    for s in lights:
        for t in bounces: ...

There is a beautiful elegance to this. It is a good way to learn how to do computer graphics. Unfortunately, this kind of architecture always leads to bad complexity that looks like this: O(f1*f2*f3*f4 ...).

Rasterizers have a better basic architecture. Scatter-gather type architecture tends to lead to nice complexity like this: O(f1)+O(f2)+O(f3)+O(f4). Don't take my word for it, look at the history. The O(N*L) immediate rasterizer got broken up into the O(N)+O(L) deferred rasterizer as soon as enough memory became available. Indirect lighting followed the same pattern.

I'm not saying that ray tracers will always be slow. But, I _am_ saying that if ray tracers ever become fast again, it will be because they have been architecturally restructured into something that looks a lot like a rasterizer. In such a case, any claimed victory by the ray tracer would be a pyrrhic one.

Comment $ per capita (Score 1) 367

$578M for 4,200 students comes out to $137k per student. The article cites "land costs" as one of the reasons for the price tag. This isn't a fair comparison, but to put it into perspective for non-Californians, homes are really expensive here. A home for 4 in an average area can easily cost you $600k. If you want to live in an area with low crime then expect to pay over $1M. Anyway, 4 people for $600k is $150k per person which is comparable to the school.

Comment Re:It is NOT 3d, you CANNOT get 3d from a 2d scree (Score 1) 255

It's not 3D, and it can never be 3D because human eyes are unable to collect 3D data. Human eyes collect 2D images only. Our brains perceive 3D environments by interpreting 2D images. This is in contrast to, for example, bats that can actually acquire 3D data by echolocation.

Enough with the nitpicking, now I will explain why you are still wrong even if we set aside the physical data acquisition issue. Humans perceive 3D by two main methods: stereopsis[1] and parallax[2]. Stereopsis is the synthesis of depth from binocular images. Parallax is depth perception by comparing relative motion from two different monocular images. Stereopsis is limited by the binocular separation distance. Therefore, we use stereopsis up close, and parallax far away. "Up close" can mean anywhere from 10 meters to 700 meters. This reference[3] has a short, easy to read treatment of various factors that affect stereopsis range.

Executive summary: 3D movies will never be really 3D because they cannot simulate parallax.

[1] http://en.wikipedia.org/wiki/Stereopsis
[2] http://en.wikipedia.org/wiki/Parallax
[3] http://arapaho.nsuok.edu/~salmonto/vs3_materials/Lecture14.pdf

Comment Use case? (Score 1) 269

When would I possibly want to use a kill switch?

Today, if I wanted to shut down the internet, I would phone up all the ISPs and ask them to turn off all the routers because of a clear danger to the nation. A kill switch would only be useful in the case that the ISPs refuse to turn off the routers. Why would they refuse? Their refusal is probably a good indication that the danger isn't as bad as I think. But maybe it really is, so I chould explain it to them. Since it is a real danger, they will obviously agree to turn off the routers. But, they still refuse to turn off the routers, so maybe the danger isn't that clear. But it is, so let me explain it to them again. After all, I'm right and hundreds of experts are wrong. I feel like I'm running in circles. Aw fuck it, let's just hit the kill switch. Much easier than actually understanding the situation and trying to figure out why hundreds of experts don't agree with me.

tldr; the only use case for a kill switch is to force people to do your bidding. That's not smart when the people you are overriding are the knowledge domain experts.

Comment Re:Wet Dream For Publishers (Score 1) 115

Game publishers are going to be all over this technology if they can make it work because it means the game source code never has to be released and, implemented correctly, the games will be impossible to crack. I'm not too happy about it, but it's the future. If not now, probably this decade or early next.

+1 Insightful. This is what MAFIAADRMFAGS want. And as persistent they are and with as much pull in the industry as they have, they will get it. They say we have purchasing power with the dollar to sway the market. But IMO, wallet power does not compare to litigation or lobbyist power, and hence WE. ARE. FUCKED.

OnLive is the next generation of Steam. It provides useful functionality (hardware independence and session state) on top of the base game itself so some people will prefer it over the alternative. OnLive means that the game will not be published. It will remain a private document stored on a server. There is nothing to make a copy of, since the game itself will never actually be published. Since nothing has been published, the entire issue of "is piracy allowed or disallowed" is meaningless.

Your claim of being harmed or diminished in some way because you cannot pirate the game is ridiculous. Piracy is tolerated in some social circles because copyright infringement doesn't actually harm anybody in a digital economy, but don't mistake tolerance for entitlement. We, as a society, do not entitle people with the right to make copies of private documents. OnLive is quite clever, because games will effectively be protected by the 4th Amendment. No copyright laws needed.

I see this as a very positive direction for a digital society. This approach allows someone to publish a document in two pieces. The first part is a private document which is protected by privacy laws. The second part is a public document which is useless on its own, but becomes valuable when connected to the private document by a network protocol. If this becomes an effective way for creators to earn a living, then we can get rid of the self-destructive, contradictory, unfair, and unenforceable copyright laws.

Comment Re:Good Fix... (Score 1) 460

The price of a transaction defines the price of the stock. It says nothing about the true value. Equating price with true value is meaningless since it is circularly defined. When x = f(x), x can be unstable. It can diverge to +infinity, -infinity, or oscillate. True value is a real number, perhaps unknowable. A well designed financial system would put limits on f(x) to ensure that the price converges to an approximation of the true value. In my opinion the US stock market doesn't do that. I am no longer convinced that the US stock market serves any useful purpose in defining the true value of anything.

Comment Re:Good Fix... (Score 1) 460

Explain how stock trading liquidity is a benefit in and of itself

The higher the liquidity, the lower the bid-ask spread. Illiquid assets have gigantic spreads, to the tune of tens of percentage points on their actual value.

... which results in some money being moved from one person's pocket to another person's pocket. There is no benefit to society. Grow some food, build a spaceship, organize an event, create a product, extract energy from the universe, change the momentum of something, increase or decrease entropy. Do something!

Comment Re:What is the value of this market speculation? (Score 1) 643

Oh, I get it. You provide liquidity. That makes a lot of sense. Let me see if I have this right.

Let's say there's a car factory that is desperate to get some steel so they can make cars. They're willing to pay 100$ for steel.

And, there's a steel mill that's desperate to sell some steel. They would be willing to accept as low as 1$ for steel.

Unfortunately, the mill and factory workers aren't salesmen. They can't find each other in the world economy. This is where you enter the picture. You provide liquidity! You analyze the market, determine that a fair value for steel is 60$, then you facilitate the trade of steel between the mill and the factory. Everybody wins. The world economy is better off; by working together we were able to turn some useless steel into useful cars.

But, that's not true, is it? You buy the steel for 1$ and sell it to the factory for 100$. Providing liquidity was just a side effect of your greed. If your trading activities didn't actually provide any liquidity you wouldn't make any special effort to make sure it happened. You don't facilitate trade to make the world a better place. You're just trying to stuff your pockets with as much money as possible.

Comment news for morons (Score 1) 163

"Wet" Asteroids Could Supply Space Gas Stations

Do we really have to have headlines like this? Why not just call it an "Ice Asteroid"? That would be accurate and there would be no need to resort to the 'Wet' label, as if this was some new kind of asteroid. Are we so stupid that we have to call it a "Gas Station"? Just say fuel. Did someone think that would be too confusing? Have we devolved to a state where most slashdot readers cannot comprehend that a fueling station serves the same purpose that a gas station provides for cars?

Comment math, sigh ... (Score 1) 449

This thread is a good example of how our generation was taught math wrong. I'm talking about the +5 responders, not the people in the article. Most people in this discussion are saying that the number of votes needed is 137.33 based on multiplying 206 by 2/3. The fact that all of the upvoted responders used arithmetic belies the failure of our math education system. Arithmetic has its place, but not here. This is a simple number problem. 2/3 is twice 1/3, so the number of yea votes must be twice the number of nay votes. Obviously the vote failed because 136 is less than twice 70. Using arithmetic is unnecessary and overly complicates the issue. We don't need any discussion about repeating digits or order of operations. I think Lockhart said it best.

Comment Re:Too bad Obama doesn't share the American dream (Score 1) 455

... his plan avoids the stepping stone God dropped in fron of us just because we've stepped there before ... did the polynesian's discover Hawaii without exploring neighboring Polynesian islands? Did the Europeans venture to the New World without exploring the Mediterranean?

It's a sad day for Slashdot that this garbage got modded up.

The moon is not a stepping stone. The moon is a gravity well. You don't go down a gravity well. You stay away from it as much as possible. The correct analogy would be: did the polynesian's discover Hawaii without exploring the Mariana Trench? Did the Europeans venture to the New World without exploring the Laurentian Abyss?

Comment Re:News Flash: Apple limits app store! (Score 1) 664

His definition is clear. You are suggesting that it might by misinterpreted. Well, that's why we have courts.

I support the distributors' right to distribute selectively but only as long as that does not cause harm to society. There is plenty of precedent for restricting the rights of business owners. For example, a restaurant owner has the right to refuse service to any customer, but they can not refuse on the basis of race or religion. I don't see any problem with a rule like that. I can support Apple having the right to selectively distribute works, but only if their selection process supports an open and free society. There's a line somewhere and in my opinion Apple has crossed it.

Comment Re:On Stallman (Score 2, Interesting) 228

Copyright arguments revolve around distributing other people's copyrighted works because we don't recognize their ownership of the copyright. We feel entitled to their work, because it doesn't actually belong to them. The original crime was the assignation of the copyright. Just as France refuses to recognize Scientology as a religion, I refuse to acknowledge the assignation of many kinds of copyrights.

I am not happy about being in this state, but after many years of seeing the effect of copyrights and other intellectual property entitlements on the computer industry and entertainment media my conclusion is that these forms of copyright do not benefit society. Like a CA gone bad, I have essentially put these copyrights on my ignore list. Like jaywalking across an empty street with clear visibility, I will infringe on any unjust copyrights when that infringement causes no harm to society and does not deprive anyone of their livelihood.

Telling me that I'm wrong because some human being in Washington D.C. stamped a form is not going to change my mind. Might does not make right. Stamping a form does make you the owner of something. True ownership comes when society recognizes the stamped form as valid and just. Do you understand the issue now? It's not about what constitutes infringement or piracy. It's about whether or not copyright assignments are just.

Slashdot Top Deals

In order to get a loan you must first prove you don't need it.