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As I mentioned below, the only technique that produces effective results is if you mix actual, real footage with CG. It's true that people can't spot the CG in

As I mentioned below, the only technique that produces effective results is if you mix actual, real footage with CG. It's true that people can't spot the CG in that situation, but that's different from the discussion of how to create fully-simulated realistic video. I'll give you a simple way to defeat any question of whether we know how to make something look real: What does it mean to multiply two colors? If you chase down the logic, the true answer is "It's meaningless. It just happens to be an approximation that looks good in most cases." But it has nothing to do with how light works in real life. Yet every engine multiplies colors because the alternative is too computationally expensive -- and it still wouldn't produce realistic results because we don't source our art from real life. Artists typically control the content, and any art-driven pipeline is doomed to look pretty good but not real.

dahart 9y ago
> the only technique that produces effective results is if you mix actual, real footage with CG This isn't true. > I'll give you a simple way to defeat any question of whether we know how to make something look real: What does it mean to multiply two colors? If you chase down the logic, the true answer is "It's meaningless." It's not meaningless at all, it's a close approximation of light absorption that happens to be measurably and perceptually indistinguishable from the physical spectral absorption process, save for a few corner cases that are being worked on. If the result is 99.9% accurate physically, and 100% perceptually indistinguishable to humans, then it's a valid predictive physical model. It has everything to do with the result of what light does in real life, and if it didn't, we wouldn't be using it to approximate light. Your thinking here seems to back up my suggestion that you might have missed out on some of the recent developments. Subsurface scattering, for example, is modeling absorption more phyically, and replacing the simple multiplication with a simulation process, because we now have the computational power to do so. Your argument is attacking the non-simulation aspects of rendering without addressing whether a simulation that is simpler than real life is acceptable. If I can't tell the difference, does it count? Because I'm 100% certain that color multiplication is not the problem when it comes to CG not looking real.
- sillysaurus3 9y ago
  It's not meaningless at all, it's a close approximation of light absorption that happens to be measurably and perceptually indistinguishable from the physical spectral absorption process, save for a few corner cases that are being worked on. It's amusing that you brush it off with "Oh, there are a few corner cases." Those corner cases are why it doesn't look real. And no, it's not 99.9% accurate. You may be thinking of constrained scenes, where e.g. you shine a laser on a substance of a specific color and then measure the resultant color combination. But the complexity of real life defies such analysis. If you're going to say I've missed some recent work, you'll need to cite sources. Then we can debate those. EDIT: To clarify: Your argument is attacking the non-simulation aspects of rendering without addressing whether a simulation that is simpler than real life is acceptable. If I can't tell the difference, does it count? My argument is that if you get a bunch of people together, show them simulated video and real video, and ask "Which of these are simulated?" they will correctly identify the simulated video as "not real" with significant accuracy -- given modern techniques, probably >95% accuracy. The simulation needs to be of a non-trivial scene, like a waterfall or a valley. When you show real video side-by-side with simulated techniques, there's no contest. If we truly knew how to make simulated video that looks real, without mixing any real-life footage, then the observers in the above scenario wouldn't be able to do any better than random chance. But they can, because we can't.
  - dahart 9y ago
    I did cite a source: subsurface scattering is an example of simulating light absorption. It is an example of things that you just claimed aren't getting better actually getting better. You're attacking my arguments and getting more hyperbolic without any examples. What specifically doesn't look real? What are you actually claiming? What is your criteria for whether something is "real"? What corner cases are you thinking of that cause color multiplication to break down so frequently that it's a bad approximation most of the time? Can you give some examples of state of the art CG that intended to improve realism but doesn't look real? I'm not claiming that everything looks real, nor that all CG is realistic. I'm claiming that CG is getter better over time, and that some things are already indistinguishable from real. The number of CG things that look realistic is going up over time, and it used to be 0. There is a trend here that reality contradicts your original basic thesis that nobody can rendering something realistic. My 99.9% number wasn't a claim, it was a made up number (which I thought was obvious, sorry). I said "If the result is 99.9% accurate... then it's a valid model" to back a point: the point is that if multiplication is predictive then it's a valid model. That's how all of physics works. Acceleration under gravity is an approximation. You haven't demonstrated that multiplying doesn't work, you've only stated an opinion. I'd like to see some examples of what you mean, because it appears to work very well from where I'm sitting. The colors of grass, bricks, wood -- diffuse materials -- is very closely approximated by multiplication, enough that we can in fact measure how good the approximation is, and humans cannot tell the difference. Therein lies the problem with your argument -- if I can't tell the difference, that is my definition of realistic. It doesn't matter what happened under the hood. You seem to be claiming that only reality is good enough to be realistic, because anything else is cutting corners. I'm not sure I understand what you mean about real life defying BRDF measurement. One of the ways that CG is getting more realistic is precisely through various gonioreflectometers, some of which shine lasers and measure the output from all angles. Material catalogs are currently being constructed and sold to CG companies using higher and higher resolution measurements of exactly what you're claiming isn't possible and doesn't help. People buy them because they improve realism. > My argument is that if you get a bunch of people together, show them simulated video and real video, and ask "Which of these are simulated?" they will correctly identify the simulated video as "not real" with significant accuracy -- given modern techniques, probably >95% accuracy. Every year Autodesk runs the test "Fake or Foto". http://area.autodesk.com/fakeorfoto http://area.autodesk.com/fakeorfoto Less than 10% of people are getting them all right this year, and a considerable number of people are under the 50% line. This isn't scientific, of course, but see if you can score 100%. This is an indicator that CG is pretty good. Will you admit it if you don't score 100%? Earlier you made an argument that stills are looking okay, but moving things aren't. The problem with that argument vs color multiplication is that color multiplication is used on stills, so if that's what's breaking down, stills should be obviously unrealistic.
kmill 9y ago
> What does it mean to multiply two colors? I wouldn't say that in a material model you're actually multiplying colors together. It just happens that when you record the amount of reflected low-, medium-, and high-frequency light under a spectrally flat light source, you can display these data as light and and perceive a color. With fancier equipment, you could record the full reflectance spectrum from every angle -- and polarization, too, why not -- and be able to predict what the (simple) material would look like under every light source. Maybe you're worrying about fluorescence, but then just record the data under varying monochromatic light sources. If you're just talking about how RGB is spectrally anemic, sure, that's why lighting your house with only R, G, and B LEDs makes everything look so strange. Spectral multiplication, as I understand it, is just a consequence of the law that if you increase the intensity of received radiation by a certain factor, then the intensity of the reflected radiation will increase by the same factor. Is there some important nonlinearity I'm missing? Where is the meaninglessness?

dahart 9y ago

> the only technique that produces effective results is if you mix actual, real footage with CG This isn't true. > I'll give you a simple way to defeat any question of whether we know how to make something look real: What does it mean to multiply two colors? If you chase down the logic, the true answer is "It's meaningless." It's not meaningless at all, it's a close approximation of light absorption that happens to be measurably and perceptually indistinguishable from the physical spectral absorption process, save for a few corner cases that are being worked on. If the result is 99.9% accurate physically, and 100% perceptually indistinguishable to humans, then it's a valid predictive physical model. It has everything to do with the result of what light does in real life, and if it didn't, we wouldn't be using it to approximate light. Your thinking here seems to back up my suggestion that you might have missed out on some of the recent developments. Subsurface scattering, for example, is modeling absorption more phyically, and replacing the simple multiplication with a simulation process, because we now have the computational power to do so. Your argument is attacking the non-simulation aspects of rendering without addressing whether a simulation that is simpler than real life is acceptable. If I can't tell the difference, does it count? Because I'm 100% certain that color multiplication is not the problem when it comes to CG not looking real.

sillysaurus3 9y ago
It's not meaningless at all, it's a close approximation of light absorption that happens to be measurably and perceptually indistinguishable from the physical spectral absorption process, save for a few corner cases that are being worked on. It's amusing that you brush it off with "Oh, there are a few corner cases." Those corner cases are why it doesn't look real. And no, it's not 99.9% accurate. You may be thinking of constrained scenes, where e.g. you shine a laser on a substance of a specific color and then measure the resultant color combination. But the complexity of real life defies such analysis. If you're going to say I've missed some recent work, you'll need to cite sources. Then we can debate those. EDIT: To clarify: Your argument is attacking the non-simulation aspects of rendering without addressing whether a simulation that is simpler than real life is acceptable. If I can't tell the difference, does it count? My argument is that if you get a bunch of people together, show them simulated video and real video, and ask "Which of these are simulated?" they will correctly identify the simulated video as "not real" with significant accuracy -- given modern techniques, probably >95% accuracy. The simulation needs to be of a non-trivial scene, like a waterfall or a valley. When you show real video side-by-side with simulated techniques, there's no contest. If we truly knew how to make simulated video that looks real, without mixing any real-life footage, then the observers in the above scenario wouldn't be able to do any better than random chance. But they can, because we can't.
- dahart 9y ago
  I did cite a source: subsurface scattering is an example of simulating light absorption. It is an example of things that you just claimed aren't getting better actually getting better. You're attacking my arguments and getting more hyperbolic without any examples. What specifically doesn't look real? What are you actually claiming? What is your criteria for whether something is "real"? What corner cases are you thinking of that cause color multiplication to break down so frequently that it's a bad approximation most of the time? Can you give some examples of state of the art CG that intended to improve realism but doesn't look real? I'm not claiming that everything looks real, nor that all CG is realistic. I'm claiming that CG is getter better over time, and that some things are already indistinguishable from real. The number of CG things that look realistic is going up over time, and it used to be 0. There is a trend here that reality contradicts your original basic thesis that nobody can rendering something realistic. My 99.9% number wasn't a claim, it was a made up number (which I thought was obvious, sorry). I said "If the result is 99.9% accurate... then it's a valid model" to back a point: the point is that if multiplication is predictive then it's a valid model. That's how all of physics works. Acceleration under gravity is an approximation. You haven't demonstrated that multiplying doesn't work, you've only stated an opinion. I'd like to see some examples of what you mean, because it appears to work very well from where I'm sitting. The colors of grass, bricks, wood -- diffuse materials -- is very closely approximated by multiplication, enough that we can in fact measure how good the approximation is, and humans cannot tell the difference. Therein lies the problem with your argument -- if I can't tell the difference, that is my definition of realistic. It doesn't matter what happened under the hood. You seem to be claiming that only reality is good enough to be realistic, because anything else is cutting corners. I'm not sure I understand what you mean about real life defying BRDF measurement. One of the ways that CG is getting more realistic is precisely through various gonioreflectometers, some of which shine lasers and measure the output from all angles. Material catalogs are currently being constructed and sold to CG companies using higher and higher resolution measurements of exactly what you're claiming isn't possible and doesn't help. People buy them because they improve realism. > My argument is that if you get a bunch of people together, show them simulated video and real video, and ask "Which of these are simulated?" they will correctly identify the simulated video as "not real" with significant accuracy -- given modern techniques, probably >95% accuracy. Every year Autodesk runs the test "Fake or Foto". http://area.autodesk.com/fakeorfoto http://area.autodesk.com/fakeorfoto Less than 10% of people are getting them all right this year, and a considerable number of people are under the 50% line. This isn't scientific, of course, but see if you can score 100%. This is an indicator that CG is pretty good. Will you admit it if you don't score 100%? Earlier you made an argument that stills are looking okay, but moving things aren't. The problem with that argument vs color multiplication is that color multiplication is used on stills, so if that's what's breaking down, stills should be obviously unrealistic.

kmill 9y ago

> What does it mean to multiply two colors? I wouldn't say that in a material model you're actually multiplying colors together. It just happens that when you record the amount of reflected low-, medium-, and high-frequency light under a spectrally flat light source, you can display these data as light and and perceive a color. With fancier equipment, you could record the full reflectance spectrum from every angle -- and polarization, too, why not -- and be able to predict what the (simple) material would look like under every light source. Maybe you're worrying about fluorescence, but then just record the data under varying monochromatic light sources. If you're just talking about how RGB is spectrally anemic, sure, that's why lighting your house with only R, G, and B LEDs makes everything look so strange. Spectral multiplication, as I understand it, is just a consequence of the law that if you increase the intensity of received radiation by a certain factor, then the intensity of the reflected radiation will increase by the same factor. Is there some important nonlinearity I'm missing? Where is the meaninglessness?