14:20 I think this is how they added shades to some background elements in Ecco: Tides of Time as well (and one enemy sprite is done like the Haunting avatar sprite), it's pretty subtle there. It is also used in Lost World: Jurassic Park IIRC Adventures of Batman & Robin also uses it well. Nice vid!
There's also one extra thing that wasn't covered regarding sprites with S/H mode. Going back to 8:17, the second last colours in palette 0-2 are unaffected by foreground plane shadows, retaining there normal colour values instead. This can be seen using Sonic 2s "night mode" code, where Tails' brightest orange isn't shadowed. It's believed to be a bug in some circles, since many games simply didn't account for this. It can be used for some neat visuals though, like small lights on a character (Paprium would've really benefit from taking that into account, but they didn't), or cartoony eye logic in a dark room, probably some other usecases that don't come to mind right now.
You're absolutely correct! I debated about whether to add this bit of info but ultimately decided against it for 2 reasons: it wasn't really all that relevant unless you're actually trying to code a game, and besides the Sonic 2 night mode, which was only accessible through a debug menu, I don't think any commercial games really demonstrated this, so I couldn't have shown any examples in the video. But you're right it was an odd quirk and there's some disagreement about whether it was actually a bug or intentional.
@@WhitePointerGaming fair enough, though I haven't seen any commercial game utilise it like my examples, they usually aren't too distracting when the game intends to use S/H so it's easy to dismiss. It's noticeable with a keen eye in Bloodlines, the players light gray doesn't get effected, but that's as bad as it gets for commercial games
Yoshi Island is filled with crazy unorthodox graphical effects. You should tackle that one. Specially the bosses and enemies that make very creative use of scan-line effects to build huge morphing creatures. Most people assume that stuff are actually full-screen software rendered vectors drawn by the SFX2, but they would not animate at 60fps if so. Its all drawn by the SNES nativelly. The clever trickery under the hood of that game is criminally under-apreciated.
I remember my first time looking at the Yoshi’s Island on the Spriter’s Resource and being baffled that the raw sprites for those deformable bosses were just giant triangles. Even vividly 3D objects like the falling walls are still just triangles as a base. The base SNES features has been covered extensively but I have no clue how Yoshi’s Island achieved effects that we haven’t even been able to replicate.
@@johnclark926 Its the same concept as 2D racers, but on steroids. HDMA at every single scan-line, scrolling the BG layer to get the slice of the BG graphics that has the width you want for each horizontal line. The rendering is actually surprisingly simple, albeit ingenious. Its the actual software deriving those shapes that must be quite exoteric.
@@buzinaocara That’s fascinating. That explains why we haven’t seen anything like it since, I don’t think there’s really a modern-day HDMA equivalent and the method probably doesn’t scale well with variable resolutions. I’d love to see someone take another crack at the concept though, the looks of the deformable slime & ghost characters are still unlike anything else and I’m sure there’s more that could be done.
@@johnclark926 HDMA only made sense in systems that rendered scan-line by scan-line just-in-time. "Racing the beam" renderers. That was a way to get a picture with good enough resolution and colour depth without using that much RAM. Since PS1, Saturn, N64, these systems have been rendering to a framebuffer, where HDMA style tricks make no sense. But nothing stops one from creating distortions and morphing shapes through other means. Yoshi's Story for the n64 is quite a direct successor to Island and it is filled with it's own morphing creatures and environments, achieved through polygon meshes. It goes way further than Island did in those respects.
Yeah these effects were super juicy back in the day. Most of the games you highlighted are some of my favourites. I couldn't believe how good the Vector an graphics were the first time I saw them. I remember walking in and out of the beams trying to see the limits of the lighting too 😅
Cool to see Battle Mania Daiginjou featured here :) I would love an explanation of how Vic Tokai achieves the mode 7-like rotating cylinder background in stage 6. Great video!
12:11 Considering that the game stars some dead spirit haunting houses, it actually works as a way to differentiate him from the alive unfortunate folks inside the house, basically the shadow & highlight modes are used to cleverly show that Poltergeist is a ghost.
Great stuff! love these tech breakdowns :) I think the ZX Spectrum also did something similar, it had normal and bright modes, in the ULA it basically dropped the colors to about 75%
Yeah its true. So basically it has kind of a "tile" based color mapping. Each 8X8 pixels could only use 2 of the 8 colors. And then each tile could either be bright or a bit darker. Both two color in each "tile" was affected so it was not the easiest to use
I remember in IBM Basic shadow and highlight mode showing up on 286 for text based graphics modes. The main difference is it wasn't palette swapping but color mixing using dithering techniques.
I'm 100% with you hahaha! I've just recently discovered this channel and the very first video I saw (can't remember now which was) I immediately thought that "hey, this guy sounds a lot like Pigsy and his content is somewhat similar and both use animals as nicknames"
As usual, there's Ex-Ranza! :D Though I'm a bit surprised to not see Stage 3 mentioned... does that actually just use palette changes to get the treeline effect?
for the bonus questionv the top background may have used the thick grey edges for sprites to make the 2nd background (the "transparent layer's") chunky tile edges which may look glitchy if they hadn't put the sprite edges on there, especially doing the wavy effects, that's just my inexperienced little guess 😊.
Fantastic video! I love the "window reflection" effect in Battle Mania 2 in isolation, but the illusion is ruined by the fact that the enemy sprites don't have reflections!
Yeah that's a pity but I suspect it would have resulted in just too many sprites on screen for the hardware to handle so was likely a technical limitation. Remember all of the weapon projectile shots and other effects were sprites too.
The only games where the concept of shadow/highlight really stood out to me was when you used magic attacks in Golden Axe 1/2, in Shining Force 1/2, and definitely Vectorman. Now that you explained it I can see it happening for sure in the scrolling text background of MK3 and in Ristar. But one thing I can't understand, and I've done research into it but can't get a solid answer, is why if the Arcade Sega System C-2 uses virtually identical hardware to the Genesis shows a richer color palette in comparison? For example if you look at the Arcade version of Columns over the Genesis, it has a smoother contrast of colors to the Genesis in it's backgrounds. Even Thunder Force AC with it's title screen seems to show more greens and blue than the Genesis can do normally. Either way excellent topic and great video. 😃
According to Sega Retro, the System C-series arcade boards had an additional colour encoder that increased the colour palette: segaretro.org/Sega_System_C#Technical_specifications
From what i've read, everything came down to making the console as affordable as possible while at the same time being a serious upgrade over the NES. They even considered sprite scaling, like in their arcade boards, to be implemented, but was deemed too expensive for the average consumer.
It's a shame more Genesis developers didn't use it, but I guess it was trickier to use than SNES transparency Eg. MS's Frankenstein. Speaking of dither and transparency I was surprised the way the Genesis handled that wasn't improved and expanded on for the Saturn as most people hated the mesh polygon aesthetic. Great video, the visual debug gave me a better impression of how S&H actually works.😉
Toy Story title screen used shadow and highlight at the same time. Wish my emu had more qol features, I did really in depth shadow highlight debug stuff in it
@White_Pointer Gaming What I'd like to see is a comparison with actual examples of the SNES and MD's sprite capabilities. Because even though th SNES was supposedly superior on paper it seems the MD did a much better job with. Some game examples would be nice. And especially touch on the per scanline limit.
I always thought the SNES CPU was a bit on the slow side, but I'm just biased because I enjoyed writing 68k asm back then. It's just very straightforward and easy(nor specifically for MD, but Amiga, ST and some of the earlier SGI machines).
It's kinda cool that the Genesis' shadow/highlight can be used in so many ways, but I think the way it works is why it often looks a bit dull or garish to me, as it's not increasing colour gamut or hue really but just adding more white or black to the same set of colours. I often feel it gives games that use it too much a bit of that "Euro-art" look to be honest, which I'm not a huge fan of. If you understand what I mean there. Still, it's useful for creating some light-based effects where necessary, so long as it's not abused. I think Vector Man is one of the times where it didn't quite work visually for me personally, and the game always just has a weird dull yet garish look to it that I'm not a fan of. I do think a lot more indie/homebrew Genesis games these days are trying to take better or more advantage of it though. And, really, I think it's best used for doing exactly what it says on the tin, which is shadows and highlights. :)
The SNES still had a lot of advantages: more colours, more background layers, proper transparency and translucency, windowing/masking, HDMA effects, and more sprites on screen and per scanline. The limitations of S/H mode with it being tied to the priority system also meant it wasn't used nearly as often as it perhaps could have been.
absolutely true, the snes does have more colors,more backgrounds,a higher resolution and cool transparancy effects et… Theres is only 1 problem with the snes about it’s graphical capabilities. It cannot do it all atonce, so no mode 7 behing or in front of a background. You want high color depth, or a higher resolution? Well yeah but then you can only use 1 or 2 backgrounds. You want 4 bavkgrounds? Well yeah but at the cost of high color depth and high resolution etc… Hence those 8 restriction mode. Also the snes cpu is slow, uses dram and it only has an 8bit data bus. But the genesis cpu is fast with it’s sram chip and 16bit data bus etc… So both systems are pretty much on par with each other, i honestly don’t see or hear much differences between those 2 systems (check toy story or mickey mania for instance). Those differences are minor and most snes games only uses 90 colors. So while i was always a big snes fan and i still always will like that system over the genesis,but once i discovered those limitations of the snes , it leaves a big dirt taste in my mouth. It frustrates me often times why we were sooo fooled by those nintendo magazines in terms of technicality. As they seemingly want to make you believe that the differences between the genesis and snes is night and day, what a joke🥲🤣@@WhitePointerGaming
sega genesis did allot with very little. 62 on screen colours weren't allot. Most of the time it was like 30/40 colours at max. but it is also how you use colour. you basically can manipulate the eyes with just a few colours. Even with one or 2 colours.
Yeah or well it was 62 colors on screen. But many was the same so visually it was maybe 40-50 colors. Normally 4-5 colors in each palette was the same.
@@litjellyfish Or same ish. It did a good job with very little. Later on you could see the extra colours on snes did make a difference. it's a tough job to fill the screen with just 40 colours on screen when snes litterally threw 200 and more colours on screen. Dkcountry fillef the screen with colour.
@@ArjanSnijder it’s not so much the colors than the palette really. Megadrive could use line color split and have hounded a if color is really wanted. Also many SNES games often did not use so much colors and still looked better (say a game that did not have so much hues in it) What really made a difference was that MD only has 8 intensity/ hue steps whole SNES had 4x that. Resulting in that you could have much more subtler finer tones. And that could the MD really never escape regardless of all the different tricks it could use to achieve more than 64 colors on screen And yeah it was difficult and required more planning. You often needed to choose between more varied art with less different colors or more “dynamic” art with less unique colors (as you needed those duplicated colors to blend between each tile palette so to speak.) What I found frustrating more was that you had no real space to do palette tricks. Like in the clip to be able to shade or make effect with colors of the main character you needed to reserve one of the 4 palettes for it + suddenly the rest of the graphics had 25% less colors. While on SNES you might not really need to use all palettes so you had some to parade to use for color animation fxs
Erm, Buddy, that's not how it works. The Mega Drive is 9 bit RGB i.e. 3 bits for red, 3 bits for green and 3 bits for blue. 8 reds times 8 greens times 8 blues = 512. When you apply Shadow and Hightlight mode together you get 7 extra unique shades of red, green and blue. So it's 15*15*15 = 3375, not 1536 or 1024. I got this information from Jon Burton's Coding Secrets RUclips channel in relation to his game Toy Story. So it's straight from the horse's mouth.
I've seen the video, in fact I mention it in this video and it's linked in the description, but he gets his calculations a little out of order at that part. S/H isn't applied to every red, green and blue shade individually to increase the number of shades of each from 8 to 15 before multiplying 15x15x15 to get the total colour count. It's applied to the full, final 512 colour count. You multiply 8x8x8 THEN S/H is applied. It's applied to the RGB values of each of those 512 colours making each of them darker (half) or brighter (double). It happens at the register level to change the shading of specified tiles or pixels - the tile or pixel is first drawn with one or more of the base 512 colours, then S/H is applied to darken or brighten it. I have some other resources linked in the description for further reading if you're interested: danibus.wordpress.com/2019/09/13/14-aventuras-en-megadrive-highlight-and-shadow/ segaretro.org/Sega_Mega_Drive/Shadow_and_highlight huguesjohnson.com/programming/genesis/palettes/
![Seungmin "그렇게, 천천히, 우리(As we are)" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/kAzmhLHePqU/mqdefault.jpg)
14:20 I think this is how they added shades to some background elements in Ecco: Tides of Time as well (and one enemy sprite is done like the Haunting avatar sprite), it's pretty subtle there. It is also used in Lost World: Jurassic Park IIRC
Adventures of Batman & Robin also uses it well. Nice vid!
There's also one extra thing that wasn't covered regarding sprites with S/H mode. Going back to 8:17, the second last colours in palette 0-2 are unaffected by foreground plane shadows, retaining there normal colour values instead. This can be seen using Sonic 2s "night mode" code, where Tails' brightest orange isn't shadowed.
It's believed to be a bug in some circles, since many games simply didn't account for this. It can be used for some neat visuals though, like small lights on a character (Paprium would've really benefit from taking that into account, but they didn't), or cartoony eye logic in a dark room, probably some other usecases that don't come to mind right now.
You're absolutely correct! I debated about whether to add this bit of info but ultimately decided against it for 2 reasons: it wasn't really all that relevant unless you're actually trying to code a game, and besides the Sonic 2 night mode, which was only accessible through a debug menu, I don't think any commercial games really demonstrated this, so I couldn't have shown any examples in the video. But you're right it was an odd quirk and there's some disagreement about whether it was actually a bug or intentional.
@@WhitePointerGaming fair enough, though I haven't seen any commercial game utilise it like my examples, they usually aren't too distracting when the game intends to use S/H so it's easy to dismiss. It's noticeable with a keen eye in Bloodlines, the players light gray doesn't get effected, but that's as bad as it gets for commercial games
Yoshi Island is filled with crazy unorthodox graphical effects. You should tackle that one. Specially the bosses and enemies that make very creative use of scan-line effects to build huge morphing creatures. Most people assume that stuff are actually full-screen software rendered vectors drawn by the SFX2, but they would not animate at 60fps if so. Its all drawn by the SNES nativelly. The clever trickery under the hood of that game is criminally under-apreciated.
I remember my first time looking at the Yoshi’s Island on the Spriter’s Resource and being baffled that the raw sprites for those deformable bosses were just giant triangles. Even vividly 3D objects like the falling walls are still just triangles as a base. The base SNES features has been covered extensively but I have no clue how Yoshi’s Island achieved effects that we haven’t even been able to replicate.
@@johnclark926 Its the same concept as 2D racers, but on steroids. HDMA at every single scan-line, scrolling the BG layer to get the slice of the BG graphics that has the width you want for each horizontal line. The rendering is actually surprisingly simple, albeit ingenious. Its the actual software deriving those shapes that must be quite exoteric.
@@buzinaocara That’s fascinating. That explains why we haven’t seen anything like it since, I don’t think there’s really a modern-day HDMA equivalent and the method probably doesn’t scale well with variable resolutions. I’d love to see someone take another crack at the concept though, the looks of the deformable slime & ghost characters are still unlike anything else and I’m sure there’s more that could be done.
YES I would love that video
@@johnclark926 HDMA only made sense in systems that rendered scan-line by scan-line just-in-time. "Racing the beam" renderers. That was a way to get a picture with good enough resolution and colour depth without using that much RAM. Since PS1, Saturn, N64, these systems have been rendering to a framebuffer, where HDMA style tricks make no sense. But nothing stops one from creating distortions and morphing shapes through other means. Yoshi's Story for the n64 is quite a direct successor to Island and it is filled with it's own morphing creatures and environments, achieved through polygon meshes. It goes way further than Island did in those respects.
Yeah these effects were super juicy back in the day. Most of the games you highlighted are some of my favourites. I couldn't believe how good the Vector an graphics were the first time I saw them. I remember walking in and out of the beams trying to see the limits of the lighting too 😅
Cool to see Battle Mania Daiginjou featured here :) I would love an explanation of how Vic Tokai achieves the mode 7-like rotating cylinder background in stage 6. Great video!
"the mode 7-like rotating cylinder background in stage 6"--> line scrolling?
12:11 Considering that the game stars some dead spirit haunting houses, it actually works as a way to differentiate him from the alive unfortunate folks inside the house, basically the shadow & highlight modes are used to cleverly show that Poltergeist is a ghost.
Great stuff! love these tech breakdowns :)
I think the ZX Spectrum also did something similar, it had normal and bright modes, in the ULA it basically dropped the colors to about 75%
Yeah its true. So basically it has kind of a "tile" based color mapping. Each 8X8 pixels could only use 2 of the 8 colors. And then each tile could either be bright or a bit darker. Both two color in each "tile" was affected so it was not the easiest to use
I remember in IBM Basic shadow and highlight mode showing up on 286 for text based graphics modes. The main difference is it wasn't palette swapping but color mixing using dithering techniques.
your voice sounds like my master teacher pigsy, subscribed indeed
Haha thanks for the sub, I don't really think I sound like him though :)
@@WhitePointerGaming Yeah, you guys don't sound alike.
I'm 100% with you hahaha!
I've just recently discovered this channel and the very first video I saw (can't remember now which was) I immediately thought that "hey, this guy sounds a lot like Pigsy and his content is somewhat similar and both use animals as nicknames"
Hi White_Pointer Gaming, great video ! Thanks.
As usual, there's Ex-Ranza! :D Though I'm a bit surprised to not see Stage 3 mentioned... does that actually just use palette changes to get the treeline effect?
for the bonus questionv the top background may have used the thick grey edges for sprites to make the 2nd background (the "transparent layer's") chunky tile edges which may look glitchy if they hadn't put the sprite edges on there, especially doing the wavy effects, that's just my inexperienced little guess 😊.
Fantastic video! I love the "window reflection" effect in Battle Mania 2 in isolation, but the illusion is ruined by the fact that the enemy sprites don't have reflections!
Yeah that's a pity but I suspect it would have resulted in just too many sprites on screen for the hardware to handle so was likely a technical limitation. Remember all of the weapon projectile shots and other effects were sprites too.
The only games where the concept of shadow/highlight really stood out to me was when you used magic attacks in Golden Axe 1/2, in Shining Force 1/2, and definitely Vectorman. Now that you explained it I can see it happening for sure in the scrolling text background of MK3 and in Ristar. But one thing I can't understand, and I've done research into it but can't get a solid answer, is why if the Arcade Sega System C-2 uses virtually identical hardware to the Genesis shows a richer color palette in comparison? For example if you look at the Arcade version of Columns over the Genesis, it has a smoother contrast of colors to the Genesis in it's backgrounds. Even Thunder Force AC with it's title screen seems to show more greens and blue than the Genesis can do normally. Either way excellent topic and great video. 😃
According to Sega Retro, the System C-series arcade boards had an additional colour encoder that increased the colour palette: segaretro.org/Sega_System_C#Technical_specifications
From what i've read, everything came down to making the console as affordable as possible while at the same time being a serious upgrade over the NES. They even considered sprite scaling, like in their arcade boards, to be implemented, but was deemed too expensive for the average consumer.
It's a shame more Genesis developers didn't use it, but I guess it was trickier to use than SNES transparency Eg. MS's Frankenstein. Speaking of dither and transparency I was surprised the way the Genesis handled that wasn't improved and expanded on for the Saturn as most people hated the mesh polygon aesthetic. Great video, the visual debug gave me a better impression of how S&H actually works.😉
The fact that it conflicts with something as basic as Priority makes it so hard to use effectively.
Esse video bem interessante pra mostrar que não é só apenas Toy Story e Vectroman que utiliza dessa técnica.
I've been here for a while and I have to say your sub count is a war crime at this point.
Thank you, I'd really appreciate it if you can spread the word to help the channel grow :)
Toy Story title screen used shadow and highlight at the same time. Wish my emu had more qol features, I did really in depth shadow highlight debug stuff in it
Yes, I talk about Toy Story's high-colour static screens (of which the title screen is one) in the video.
@White_Pointer Gaming
What I'd like to see is a comparison with actual examples of the SNES and MD's sprite capabilities. Because even though th SNES was supposedly superior on paper it seems the MD did a much better job with. Some game examples would be nice. And especially touch on the per scanline limit.
I always thought the SNES CPU was a bit on the slow side, but I'm just biased because I enjoyed writing 68k asm back then. It's just very straightforward and easy(nor specifically for MD, but Amiga, ST and some of the earlier SGI machines).
@@Dr.MSC.W.Krueger It was slower depending on case. But the SNES also had some extra coprocessor if I recall but few if any games used it
very good, thanks.
It's kinda cool that the Genesis' shadow/highlight can be used in so many ways, but I think the way it works is why it often looks a bit dull or garish to me, as it's not increasing colour gamut or hue really but just adding more white or black to the same set of colours. I often feel it gives games that use it too much a bit of that "Euro-art" look to be honest, which I'm not a huge fan of. If you understand what I mean there. Still, it's useful for creating some light-based effects where necessary, so long as it's not abused. I think Vector Man is one of the times where it didn't quite work visually for me personally, and the game always just has a weird dull yet garish look to it that I'm not a fan of. I do think a lot more indie/homebrew Genesis games these days are trying to take better or more advantage of it though. And, really, I think it's best used for doing exactly what it says on the tin, which is shadows and highlights. :)
its more like a graphite unique color
@@rafaelantonio6765 I'm not quite sure what that means?
@@inceptional i mean shadow highlight only uses 1 color for transparency on sega genesis
@@rafaelantonio6765 Ah, okay, got you.
Yeah it washes things out. A bit similar to the Amigas halfbright mode.
With these hidden stuffin mind, the genesis is pretty much on par with the snes graphically.
Thing is i underestimated the sega genesis capabilities.
The SNES still had a lot of advantages: more colours, more background layers, proper transparency and translucency, windowing/masking, HDMA effects, and more sprites on screen and per scanline. The limitations of S/H mode with it being tied to the priority system also meant it wasn't used nearly as often as it perhaps could have been.
absolutely true, the snes does have more colors,more backgrounds,a higher resolution and cool transparancy effects et…
Theres is only 1 problem with the snes about it’s graphical capabilities.
It cannot do it all atonce, so no mode 7 behing or in front of a background.
You want high color depth, or a higher resolution? Well yeah but then you can only use 1 or 2 backgrounds.
You want 4 bavkgrounds? Well yeah but at the cost of high color depth and high resolution etc…
Hence those 8 restriction mode.
Also the snes cpu is slow, uses dram and it only has an 8bit data bus.
But the genesis cpu is fast with it’s sram chip and 16bit data bus etc…
So both systems are pretty much on par with each other, i honestly don’t see or hear much differences between those 2 systems (check toy story or mickey mania for instance).
Those differences are minor and most snes games only uses 90 colors.
So while i was always a big snes fan and i still always will like that system over the genesis,but once i discovered those limitations of the snes , it leaves a big dirt taste in my mouth.
It frustrates me often times why we were sooo fooled by those nintendo magazines in terms of technicality.
As they seemingly want to make you believe that the differences between the genesis and snes is night and day, what a joke🥲🤣@@WhitePointerGaming
Sub’d. Look forward to more MD content. Cheers
sega genesis did allot with very little. 62 on screen colours weren't allot. Most of the time it was like 30/40 colours at max. but it is also how you use colour. you basically can manipulate the eyes with just a few colours. Even with one or 2 colours.
Yeah or well it was 62 colors on screen. But many was the same so visually it was maybe 40-50 colors. Normally 4-5 colors in each palette was the same.
@@litjellyfish Or same ish. It did a good job with very little. Later on you could see the extra colours on snes did make a difference. it's a tough job to fill the screen with just 40 colours on screen when snes litterally threw 200 and more colours on screen. Dkcountry fillef the screen with colour.
@@ArjanSnijder it’s not so much the colors than the palette really. Megadrive could use line color split and have hounded a if color is really wanted. Also many SNES games often did not use so much colors and still looked better (say a game that did not have so much hues in it)
What really made a difference was that MD only has 8 intensity/ hue steps whole SNES had 4x that. Resulting in that you could have much more subtler finer tones.
And that could the MD really never escape regardless of all the different tricks it could use to achieve more than 64 colors on screen
And yeah it was difficult and required more planning. You often needed to choose between more varied art with less different colors or more “dynamic” art with less unique colors (as you needed those duplicated colors to blend between each tile palette so to speak.)
What I found frustrating more was that you had no real space to do palette tricks. Like in the clip to be able to shade or make effect with colors of the main character you needed to reserve one of the 4 palettes for it + suddenly the rest of the graphics had 25% less colors.
While on SNES you might not really need to use all palettes so you had some to parade to use for color animation fxs
Erm, Buddy, that's not how it works. The Mega Drive is 9 bit RGB i.e. 3 bits for red, 3 bits for green and 3 bits for blue. 8 reds times 8 greens times 8 blues = 512. When you apply Shadow and Hightlight mode together you get 7 extra unique shades of red, green and blue. So it's 15*15*15 = 3375, not 1536 or 1024. I got this information from Jon Burton's Coding Secrets RUclips channel in relation to his game Toy Story. So it's straight from the horse's mouth.
I've seen the video, in fact I mention it in this video and it's linked in the description, but he gets his calculations a little out of order at that part. S/H isn't applied to every red, green and blue shade individually to increase the number of shades of each from 8 to 15 before multiplying 15x15x15 to get the total colour count. It's applied to the full, final 512 colour count. You multiply 8x8x8 THEN S/H is applied. It's applied to the RGB values of each of those 512 colours making each of them darker (half) or brighter (double). It happens at the register level to change the shading of specified tiles or pixels - the tile or pixel is first drawn with one or more of the base 512 colours, then S/H is applied to darken or brighten it.
I have some other resources linked in the description for further reading if you're interested:
danibus.wordpress.com/2019/09/13/14-aventuras-en-megadrive-highlight-and-shadow/
segaretro.org/Sega_Mega_Drive/Shadow_and_highlight
huguesjohnson.com/programming/genesis/palettes/
since we now have MSU technology. genesis is stiil inferior when it comes to pallete colors
Shadow and highlight allows the MD to display up to 192 colors on screen ingame. the SNES mostly use 128 colors in games.