I may have covered this previously, but: Some fun(?) technical background on exactly *why* various CD-i games had these sorts of cutscenes.pic.twitter.com/6yRCBzVcbn
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MPEG decompression was simply not supported unless you had a Digital Video Cartridge, or had a model from pretty far into the console's life cycle, when manufacturers would sometimes integrate DVC compatibility into the console itself.
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The standard video hardware of the CD-i was an odd thing: One of the video modes (and the only way to break out of palettized color) was "delta YUV", where you'd specify the starting values in YUV color space, then each following sample was a delta against the current value.
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This was what a handful of games used to play FMVs within a small, limited on-screen window, since it provided enough color fidelity to be worthwhile.
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Beyond that, it's important to keep in mind that the baseline CD-i spec was sporting a 1x-speed CD: The best you could get, assuming continuous transfer with no seeking, was 150 kilobytes a second coming off of the disc.
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Given that a full frame of 320x240 pixels at 16-bit color resolution is exactly 150 kilobytes, that would seem to mean that the best you could hope for is a "video" running at one frame per second. That's not a video, that's a slide-show. So, how do we solve it?
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Well, the Apple IIgs had a prescient aspect of its own video hardware: It supported run-length encoding (RLE) for graphics. The CD-i spec called for video hardware that could do RLE, too. In English: RLE is a value and a repeat count. "Blue, 25 times" instead of "blue blue bl...
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This was the key to compressing cutscenes to be small enough that they could be streamed at a reasonable frame rate. You'd load up a static background on one video plane, then stream RLE cartoons onto the second plane, layered on top. Easy.
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Now, none of this is meant to defend or approve of the atrocious art found in the CD-i Zelda games, or Hotel Mario. As RLE fills were limited to a single line (I believe), I can't think of a reason why some amount of shading couldn't have been done, as long as it was vertical.
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Beyond that, the art style was a grotesque caricature of humanity, more resembling strips of flesh welded to a metal frame, more resembling Animal Soccer World or Aladin from Dingo Pictures than any sort of memorable cartoon. But that's not the console's fault.
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So: Why did CD-i games have flat-shaded cartoons? To stream off of a 1x-speed disc, they had to. Why was the artwork so terrible? Blame the developers on that one. The CD-i itself was remarkably capable. That same RLE mode could have been used to do Starfox before Starfox.
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