[HN Gopher] The art of the shadow: How painters have gotten it w...
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The art of the shadow: How painters have gotten it wrong for
centuries
Author : webmaven
Score : 111 points
Date : 2023-02-14 17:38 UTC (5 hours ago)
(HTM) web link (thereader.mitpress.mit.edu)
(TXT) w3m dump (thereader.mitpress.mit.edu)
| nyanpasu64 wrote:
| Interestingly, many shadow inaccuracies appear in 3D video games,
| due to a combination of rasterization hacks to approximate light
| transmission and rendering (player shadows appearing withing
| stage shadows, shadows appearing _above_ players standing below a
| platform), and deliberate artistic liberties to make games easier
| to play (Mario Sunshine 's level shadows are cast from the sun,
| but tree and player/enemy shadows appear directly below
| characters to make it easier to judge jumps).
| mfost wrote:
| That's pretty old 3D rendering tricks causing those overall
| though. Like I fail to see recent games doing those at all.
|
| Overall, shadows aren't the hard part nowadays, it's light that
| is. Global illumination and light bouncing back around that is.
| Though shadows ARE very expensive still.
| viraptor wrote:
| It's getting better, but correct shadows cast on dynamic
| objects are still a relatively recent thing. Can't test now,
| but i would bet some modern titles still only do shadows on
| static geometry on lower settings.
| baabaloo wrote:
| [dead]
| adwf wrote:
| Would've been worth comparing to Vermeer for some examples of
| excellent shadows.
| psygn89 wrote:
| I was told by my art teacher in high school that they
| intentionally didn't go for total realism as that was imitating
| God's work or some religious reasoning (they cared more about the
| story/theme than the execution). I never really bought into that
| reasoning 100% as they seem to get really detailed with the
| furniture and clothing for instance, but then fall flat with the
| perspective/shadows.
| dkarl wrote:
| > I was told by my art teacher in high school that they
| intentionally didn't go for total realism as that was imitating
| God's work
|
| I heard this story as well and always suspected that it was an
| urban legend. I heard the same story about a Buddhist painter
| who intentionally added a poor brushstroke to every painting,
| to reflect that everything is imperfect and changing. Neither
| story makes sense in the context of Christian belief or
| Buddhist conviction. A Christian would have to be incredibly
| arrogant to think they had to take special measures to avoid
| rivaling the work of God -- it would be hard to call such a
| person Christian. Similarly for the Buddhist. If they believed
| that everything that can be experienced has a certain
| characteristic, then it wouldn't be necessary to impose that
| characteristic on their artwork.
| themodelplumber wrote:
| This reminded me of my own journey of interest in, and work with
| representing shadows...
|
| After one month of CGI learning, interest levels were like this:
|
| https://www.creativeshrimp.com/wp-content/uploads/2014/12/cg...
|
| 15 years later, this is just about what comes to mind when I read
| the article:
|
| https://photodoto.com/wp-content/uploads/2013/01/24-shadow-a...
|
| Shadows as a concept are, let's say, much more flexible in my
| mind now...
|
| It might have something to do with alternately being told that
| some of my real photos were obvs fake, and that some of my
| realistically-rendered (per spec) shadows for product marketing
| needed to change in the fake direction, in order to fit the
| needed composition better.
|
| After that I decided that all shadows would go in the cow
| direction whenever I felt like it, no matter how the scene was
| actually modeled.
| taneq wrote:
| The cow direction is clearly superior.
|
| Where's the tail come from, though? That's the only bit I can't
| figure out.
| korroziya wrote:
| Slightly misleading title, seeing as how a lot of them were
| getting it wrong on purpose.
| 6gvONxR4sf7o wrote:
| Hopefully the title doesn't turn people off of it, because the
| subtitle makes it clearer and article is great.
| RC_ITR wrote:
| "They did it on purpose" is actually a great answer to "How did
| they get it wrong for Centuries?"
| shahar2k wrote:
| nothing helped me paint light and shadow more than doing 3d
| renders and seeing how light bounces and bends in an isolated
| environment.
| bee_rider wrote:
| Lots of comments about how they are probably doing it for
| artistic reasons, or as reasonably and ignorable approximations,
| which are almost certainly correct. But it is much funnier to
| read the headline as inter-field shit talking.
|
| "Wow painters have been screwing this up for centuries. It only
| took a couple decades for programmers to figure out ray tracing.
| Git gud art scrubs."
| guestbest wrote:
| The purpose of the artist with patronages is not to be a camera
| but to reflect a more attractive vision of the subject. Also
| paintings aren't photography so the artist has more liberty to
| alter details to better fit a composition
| freitzkriesler2 wrote:
| Pretty sure they were doing this on purpose because art prior to
| the impressionists was done intentionally to convey subtler
| meanings.
|
| If I recall correctly, it was noses (or maybe it was hands) that
| artists had difficulty drawing. Been a long time since my art
| history gen Ed.
| otabdeveloper4 wrote:
| Hands. See Stable Diffusion for proof.
| tobr wrote:
| Getting shadows right is incredibly complicated. You need to
| figure out the silhouette of the object from the perspective of
| the light source, then project that silhouette over the geometry
| the shadow falls on, then draw the perspective of that projection
| from the point of view of the "camera". So it is a perspective of
| a projection of a perspective. And to add to that, objects
| occlude each other, and you might have multiple light sources.
| Since most artists probably start with a composition in the 2d
| space of the artwork, there's never really a coherent 3d space to
| place the light sources in or figure out those projections in. I
| don't think you should expect anyone to get it right in a complex
| scene unless they are drawing from reference.
| zowie_vd wrote:
| > Since most artists probably start with a composition in the
| 2d space of the artwork, there's never really a coherent 3d
| space to place the light sources in or figure out those
| projections in.
|
| Highly skilled artists don't just think in 2D -- they really do
| imagine the 3D scene that they're painting. It's hard to relate
| to but people with a lot of drawing/painting experience can
| "feel the form", as they say, when they draw. But it's true
| that figuring out the lighting is still difficult even then.
|
| I do want to point out that if you look at talented painters
| from later in history than the early renaissance, they don't
| make nearly as many mistakes as the ones in the article,
| although of course the lighting of imaginary scenes is still
| always approximated and simplified.
| treeman79 wrote:
| Took art class in college a few years ago for kicks. One of
| first things is learning to see lights and darks. Spend 3 hours
| a day for several weeks in a pitch black room with only a
| single source light. Eventually working to drawing a curtain in
| charcoal. You don't try and draw a curtain.
|
| No form to it. You just have to draw lights and shadows as you
| "see" them. At end you have a well drawn curtain.
|
| After awhile your entire perspective even outside of class
| changes. You naturally see lights and darks. Not just objects.
| waboremo wrote:
| You can get a taste of this at home, for anyone else wanting
| to experience a new perspective. Find a nice photo of a
| person, probably a 3/4 body shot (album covers are great
| too), black and white helps but color is just fine too. Flip
| the image upside down. Now sketch what you see without
| flipping the image or moving your head around, focus on what
| you see in front of you as it exists. Don't rationalize it or
| think about the grand act of drawing a person. You are just
| sketching the dark circle, or a curved line.
|
| It's a common technique when learning how to recognize lines,
| shapes, and shadows. The simple act of flipping an image
| upside down is enough for your brain to turn off it's
| automatic recognition magic that keeps you from seeing
| primary forms.
|
| Do it enough times, and like other visual artists, you start
| admiring a lot of things people take for granted about
| vision.
| shahar2k wrote:
| yup! people draw with "Shortcuts" instead of putting the
| actual value of things on the page... my favorite exercise
| was dividing a canvas into a 1" grid and taking a 1 inch
| brush and filling in each square by mixing the correct color
| one at a time like a raster, you end up with a really true to
| life pixelated painting.
| user5678 wrote:
| [dead]
| HellDunkel wrote:
| Caravaggio and Rembrandt came up with some pretty impressive
| shadows- so it always depends on the renderer. What even the
| greatest renaissance painters really could not do well is
| children!
| he0001 wrote:
| My main issue with shadows are that they are so hard to color
| right. You need the exact same color but you then need to add
| black, but I can't get that right. Reflections and such usually
| is given away from the scenery.
| beardyw wrote:
| If you are using paints, not black. You need to desaturate. Get
| a colour wheel and add the colour opposite. So yellow, add
| purple. It works.
| zowie_vd wrote:
| I don't recommend adding black to get shadow colors -- you're
| not going to get pretty colors if you take that approach.
| Shadows have a bit of a color of their own. What you need to do
| is think of the bounce light in the scene, and I'll use an
| example to explain.
|
| First of all, if you've got a sphere in deep space, its shadow
| side is going to be pure black, since there's pretty much no
| light bouncing around, and so there's no light to be reflected
| by the shadow side of the sphere. Now let's take an indoors
| scene: Imagine a room with red walls, a white floor, a single
| neutral (white light) ceiling lamp and a white sphere in the
| middle, what color is the sphere's shadow going to be? In the
| red-walled room, the shadows of the sphere would be subtly red
| -- especially in the parts of the shadow where it's facing the
| walls more than the floor. That's because the light you see in
| the shadows of an object is light that has already been
| reflected from other surfaces in the room. This reflected
| light, in the case of the red walls, is red.
|
| Of course in a more complicated scene you just approximate it.
| For an outside scene, you usually want to make your shadows
| only a bit darker and move your shadow color's hue a little
| closer to the color of the sky. But colors are difficult, you
| learn through experience really.
| Jaxan wrote:
| Not just black but also blue (if outside). De blue sky tints
| the shadows blue.
| mturmon wrote:
| Yes!
|
| The surface reflects light it scoops up from the visible
| hemisphere around it. If some of the hemisphere is sky, then
| the light cast onto that surface will be tinted blue.
|
| I'm not sure if people have access to it, but here's an
| example from an airborne imaging spectrometer that is flying
| over a partially-shadowed domed building (on the Caltech
| campus):
|
| https://www.sciencedirect.com/science/article/pii/S003442572.
| ..
|
| Figure 4 shows the dome (really a cone) - note the shadow at
| top-right.
|
| And figure 5, panel C, shows the contrast-enhanced light
| reflecting off that dome. You can see that the shadowed
| portion in the upper-right of the dome is bluer than the
| directly-lit stuff. (The directly-lit stuff is more golden,
| from the direct sunlight.)
| visarga wrote:
| No way. Humans are much smarter than SD, are they saying for
| hundreds of years we did the (not hands) shadows wrong?
| watwut wrote:
| Artists today are still getting them wrong. Art education puts
| emphasis on this stuff today, but people make mistakes.
| hobo_mark wrote:
| It still blows my mind that midjourney & co. can get decent
| illumination, shadows and even reflections. Just... how?!
| onlyrealcuzzo wrote:
| Wisdom of the crowd?
|
| It's just statistically inferring from previously seen
| images.
| simondotau wrote:
| I'm not sure that sufficiently explains an apparent ability
| to do three dimensional reasoning when performing
| statistical inference in two dimensions?
| nerdponx wrote:
| Apparently millions of shadows and billions of parameters
| is enough.
|
| Does it always get them right, or just most of the time?
| majormajor wrote:
| I've definitely seen it get reflections/lighting/shadows
| wrong. In exactly that sort of "this is an unusual
| perspective and it can't actually do the math" way.
| mc32 wrote:
| Sometimes you don't want to be "literal" or photorealistic --you
| want to portray a scene or subject "artistically" and you take
| liberties in order to highlight and de-emphasize other less
| important aspects.
|
| That said, some of the examples are funny, like where a shadow
| going up some steps stops short so as not to "overshadow" another
| subject[1] --whose shadow in turn seems to be perpendicular to
| the main shadow.
|
| [1]Madonna and Child Enthroned with Saints" (detail)
| zowie_vd wrote:
| The paintings in the article are mostly 15th century, which is
| only early renaissance. The understanding of light in painting
| was still somewhat limited in those times. I think in the case
| of almost all of these paintings it's more a matter of
| technical competence rather than artistic intention (exceptions
| include "Madonna and Child Enthroned with Saints" where I
| reckon the shadow ends early for compositional reasons). It's
| interesting to look at this to get a sense of the various ways
| people can get something wrong before someone gets it right.
| nerdponx wrote:
| It can't be _that_ hard to sketch what you see on a sunny day
| or in candlelight and start to make sense of the rules,
| right? Getting perspective to look right in paintings seems
| like it should be a more challenging invention than how
| shadows behave around corners, walls, and other objects.
| Getting the sizes and shapes of the shadows correct would be
| another matter, however.
|
| So I am willing to assume that if a shadow fails to climb up
| a wall, it's because the artist thought it looked better
| without the shadow on the wall.
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