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Shadows do get "darker" when they overlap and there's more than a single light source. 3 people illuminated by 2 lamps will project 6 shadows. Where the 6 shad
by otikik 2y ago
Shadows do get "darker" when they overlap and there's more than a single light source.
3 people illuminated by 2 lamps will project 6 shadows. Where the 6 shadows all overlap, that will be "black" (or only picking ambient light). In other places where less shadows overlap, you will get a gradient of illumination.
- deleted 2y ago[deleted]
- lukan 2y agoGood observation, but the article is not wrong (and quite interesting) "There’s just one light source, and relatively far away, so the shadow is simply an absence of light."
- fregus 2y agothat's not true, it will be black (or ambient light) when any two shadows, one from each light, intersect. that's because if it is in shadow from light A and in shadow from light B, where would it get any illumination from? only from the ambient light, or if there is none, it would be black.
- terminalbraid 2y agoNo. Consider two objects, two light sources, and an ant. An ant outside any shadow can see both light sources. An ant in a non-overlapping shadow cast from one object will have one light source blocked out but the other light source will be visible to the ant. An ant in overlapping shadows from two objects will have both light sources blocked out. (Geometrically in this case it is necessary the overlapping shadows be cast from two separated points each from distinct light sources) When one light source is visible to the ant that area must be lighter than when no sources are visible. This is the scenario presented by the OP. edit: Since people seem to not believe this you can find a representation in part E in this diagram https://i.imgur.com/r6x6QPQ.jpeg https://i.imgur.com/r6x6QPQ.jpeg and a photograph of this nicely done with colored lights here https://i.imgur.com/NUlywpb.jpeg https://i.imgur.com/NUlywpb.jpeg
- twodave 2y agoWe aren’t questioning your logic, just your reading comprehension in this case :) OP was correctly describing the case where both lights are blocked from view.
- terminalbraid 2y agoJust to summarize, because someone is missing something: otikik pointed out a case of multiple light sources where overlapping shadows will be darker (otikik is correct) fregus says "that's not correct" and argues a true case (shadows from one light source will not be darker) which is a bad argument because it tries to overgeneralize. The case from fregus is for the same light source and they cannot use this to argue otikik is incorrect because otikik's argument explicitly requires multiple light sources. I point out, responding to fregus, how otikik is correct and how you need to consider multiple sources as well as including examples and physical evidence. You question my reading comprehension for some reason
- Fraterkes 2y agoFregus point is that otikik seems to suggest that the darkest shadow will be the combination of all 6 shadows; thats obviously wrong, any shadow blocked from both lights will be as dark as any other shadow blocked from both lights, no matter the amount of "overlapping" shadows. You then respond to Fregus by unnecesarily just explaining shadows again, hence the reading comprehension comment.
- binary132 2y agoLet’s all write long explanations of one another’s long explanations, then the people who couldn’t comprehend the simple point in the first place will definitely understand
- Fraterkes 2y agoI'm not talking to "people", I'm writing a specific response to a specific person. Do try to keep up
- binary132 2y agoThat would be true if lights were simple point sources with simple straight ray behavior and no diffusion and no reflection but they’re not.
- yazzku 2y agoYou are right. fregus leaves it at "ambient light" and calls it a day, but ambient light is just an empirical construct, not grounded in physics. In reality, light bounces around, and areas will appear darker the more the light paths otherwise converging on them are blocked by occluders. I think "overlapping shadows get darker" is just not a very intuitive way to think about it because it disregards the stuff that actually matters, which is the light sources and how the scene may block their light paths. For early games that could not afford advanced methods of global illumination, making overlapping shadows get darker seems like a reasonable, though not necessarily correct, way of faking it. And the other thing ignored in these comments is perception. For the case of the two businessmen looking at their shadows under a bridge, it is easy to show with a diagram that some areas of overlapping shadows are, in fact, darker. But in such a poorly lit scene, people are likely to conclude that there is no difference, which isn't to say that there isn't one but, rather, that they don't perceive one.
- binary132 2y agoYes, definitely a big difference between reality and a pretty, fast facsimile of it!
- deleted 2y ago[deleted]