3 ms·

Involving colors is much more complicated than that; in theory if you shine white light through stack a red filter on top of blue filter, I'd expect the interse

by zokier 5y ago

Involving colors is much more complicated than that; in theory if you shine white light through stack a red filter on top of blue filter, I'd expect the intersecting area to be closer to black than purple. You can see that in for example this picture: https://www.walmart.com/ip/Sightmark-32mm-Filters/31197086 https://www.walmart.com/ip/Sightmark-32mm-Filters/31197086 This is just the tip of the iceberg when it comes to the complexity of translucent objects. To get truly convincing results spectral rendering is needed, but of course that is prohibitively expensive for real-time use.

twelvechairs 5y ago
Yes its all very loosely approximated to real life anyway when avoiding the spectral level. Its not just the filter but also the quality of light being emitted/reflected from behind - A broad spectrum light like the sun will create more even effects while narrow spectrum lights like flourescent lamps or HPS street lamps can act variably. Looking through a yellow filter at a yellow flourescent light - you could easily see almost all the original light (bright yellow) or none (black) depending on the spectral transmission of the filter.
pishpash 5y ago
Why is that any more difficult than calculating color reflection/absorption on a surface? Both presumably involve multiplication in spectrum space.
- usrusr 5y ago
  You don't have multiple of those stacked on top of each other. At least not as long as you don't dive deep into the global illumination rabbit hole. And then you've got bigger and more pressing problems to solve.
- zokier 5y ago
  Yes, you are right that conceptually it is the same problem both with reflections and transmissions. The key difference is that in typical scenes indirect/bounce lighting tends to have comparatively subtle effect whereas translucency, especially when colored, can be easily quite apparent. Colored mirrors are pretty rare but colored transparent objects are very common.
astrange 5y ago
You also need to simulate polarization (and maybe quantum mechanics) for sunglasses to work properly.
- cycomanic 5y ago
  I don't know where the quantum nature of light would come in for sunglasses, but you are correct polarisation would definitely be needed.
  - astrange 5y ago
    It's claimed that polarization is due to quantum effects. https://www.youtube.com/watch?v=zcqZHYo7ONs https://www.youtube.com/watch?v=zcqZHYo7ONs …I think it actually isn't and the people explaining it have just forgotten it's supposed to be a metaphor though.
    - rcxdude 5y ago
      polarization is very much a quantum effect, however the specific experiment in the video does not prove the quantum wierdness because the setup does allow a hidden variable explanation.
  - sharikous 5y ago
    Polarization of a single photon has to be treated in a QM framework , but there is no need for that with normal sources. Also, polarization as a degree of freedom arises out of symmetry considerations, and that's what you learn in QFT.

by zokier 5y ago

twelvechairs 5y ago

Yes its all very loosely approximated to real life anyway when avoiding the spectral level. Its not just the filter but also the quality of light being emitted/reflected from behind - A broad spectrum light like the sun will create more even effects while narrow spectrum lights like flourescent lamps or HPS street lamps can act variably. Looking through a yellow filter at a yellow flourescent light - you could easily see almost all the original light (bright yellow) or none (black) depending on the spectral transmission of the filter.

pishpash 5y ago

Why is that any more difficult than calculating color reflection/absorption on a surface? Both presumably involve multiplication in spectrum space.

usrusr 5y ago
You don't have multiple of those stacked on top of each other. At least not as long as you don't dive deep into the global illumination rabbit hole. And then you've got bigger and more pressing problems to solve.
zokier 5y ago
Yes, you are right that conceptually it is the same problem both with reflections and transmissions. The key difference is that in typical scenes indirect/bounce lighting tends to have comparatively subtle effect whereas translucency, especially when colored, can be easily quite apparent. Colored mirrors are pretty rare but colored transparent objects are very common.

astrange 5y ago

You also need to simulate polarization (and maybe quantum mechanics) for sunglasses to work properly.

cycomanic 5y ago
I don't know where the quantum nature of light would come in for sunglasses, but you are correct polarisation would definitely be needed.
- astrange 5y ago
  It's claimed that polarization is due to quantum effects. https://www.youtube.com/watch?v=zcqZHYo7ONs https://www.youtube.com/watch?v=zcqZHYo7ONs …I think it actually isn't and the people explaining it have just forgotten it's supposed to be a metaphor though.
  - rcxdude 5y ago
    polarization is very much a quantum effect, however the specific experiment in the video does not prove the quantum wierdness because the setup does allow a hidden variable explanation.
- sharikous 5y ago
  Polarization of a single photon has to be treated in a QM framework , but there is no need for that with normal sources. Also, polarization as a degree of freedom arises out of symmetry considerations, and that's what you learn in QFT.