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This is a great analysis of the kinds of compromise that 8 bit system designers were all making. They all made very different choices - the Cambrian explosion o

This is a great analysis of the kinds of compromise that 8 bit system designers were all making. They all made very different choices - the Cambrian explosion of different graphics architectures at the time were all different responses to how to get the coveted marketing checkbox of ‘full color high resolution graphics’. It was definitely not clear at the time which approaches were best. Could Sinclair have made a different computer? Absolutely, yes. Would it have had the same impact? Unknown. From the perspective of a programmer who grew up in the UK in the 1980s the idea that the Spectrum was a failure riddled with design mistakes is just completely ahistorical. It was the dominant home computer, it was the dominant computer gaming platform, and it sparked the careers of thousands of British coders.

nottorp 5y ago
All that smart hardware and you end up with a device that can only run side scrollers and top down jrpgs, because that's what you can do with a tiled background and a few sprites. Could the NES run the first isometric games that showed up on the spectrum, for example? Or even some of the first primitive adventure games that used the built in graphics primitives to accompany the text with some graphics.
- kragen 5y ago
  The NES mostly couldn't, but it also had only 2K of RAM. The NES did end up with a quite faithful port of Marble Madness, but not until 01989, 5 years after the game's initial arcade release (which used a 68010!). The Spectrum port of Marble Madness was abominable, but that wasn't really the Spectrum's fault. However, the NES port did feature a full-screen viewport onto a smoothly-scrolling isometric playfield, which as far as I can tell no Spectrum game ever managed. (Maybe Golden Axe is closest?) I'm really interested in the question of how to use an NES-like tile engine to draw a 3-D world without perspective, like Fairlight, Knight Lore, half of Quazatron, Highway Encounter, The Great Escape, or Ant Attack—though remember that the Spectrum also had first-person shooters with perspective, like DeathChase, Tau Ceti, or 3D Starstrike, which maybe would have been harder to incorporate. I think there are at least four reasonable answers and one total cheat. 1. You can take an "oblique" rather than "isometric" approach, like Target Renegade, Golden Axe, and many old technical drawings. Your X-Y plane is the screen, and Z goes off at a diagonal, typically 45°. So your X vector is just [1 0], your Y vector is [0 -1], and your Z vector is, say, [1 -1]. Single tiles of surfaces in the X-Y plane are just single tiles on the screen, and that's adequate for when an X-Y surface occults a surface in any other orientation, as long as it's at a tile boundary. A tile of an X-Z (horizontal) surface becomes two right triangles, one in the lower right of a screen tile and one in the upper left of the tile to its right. Similarly, a tile of a Y-Z (vertical but not screen-parallel) surface becomes two right triangles, one in the upper left of a screen tile and one in the lower right of the tile above it. So, to make oblique renderings of axis-parallel arbitrary solid shapes out of a single X-Z texture, a single X-Y texture, and a single Y-Z texture (as in Ant Attack, though Ant Attack is isometric), all joined at tile boundaries, you need only 5 tiles: all X-Y, all X-Z, all Y-Z, and two that are half X-Z and half Y-Z. If you can have free-standing X-Z and Y-Z surfaces that occult an X-Y surface, like some of the walls in Highway Encounter, you need 4 more tiles: half X-Y and half either X-Z or Y-Z. An additional texture on the Y-Z plane costs you 3 additional tiles, or 5 with free-standing surfaces and arbitrary occultations. Similarly, non-straight edges, like in Where Time Stood Still, cost you an extra tile or two. 2. You can do "isometric" tiles with 45° angles instead of the correct 30° angles, so your X vector is [-1 -1], your Y vector is [0 -1] as before, and our Z vector is [1 -1]. This requires a larger variety of different tiles, has the same degree of geometric distortion, and might actually look worse: for a single texture on each plane you need not only the X-Y, Y-Z, X-Z, Y-Z/X-Z, and X-Z/Y-Z tiles from before, but also Y-Z\X-Z, X-Y/Y-Z, and 8 other combinations, 15 in all. 3. To do "isometric" with the correct 30° angles and only a little bit of geometric distortion, with your XYZ vectors being [-1 -½], [0 -1], and [1 -½], you can have four positions for a boundary within each tile: \ lower half, / lower half, \ upper half, and / upper half. This results in 27 tiles given one texture per plane, though not all will necessarily occur. The tradeoff for all this complexity is that now you have four colors per tile instead of two, possibly higher resolution, and faster screen updates, which enable a scrolling full-screen viewport. Note that, of the 3-D Spectrum games I mentioned above, only DeathChase, Knight Lore, and Fairlight have a nearly-full-screen viewport onto the playfield, and the latter two achieve it by having an almost totally static background with a 1–2-second "loading" pause in between rooms. By contrast, a tilemap would allow you to rapidly scroll a large viewport, as long as it was done in multiples of the tile size. 4. Instead of precomposing a pattern table that draws a full-screen "isometric" world, you can draw with total freedom into a small viewport by writing into the pattern table. (On the NES the pattern table was typically in ROM, but of course that would be impossible for a cartridgeless machine like the Spectrum.) This allows you to not only do partial occlusion effects and subpixel scrolling like The Great Escape but even perspective rendering like Driller and 3D Starstrike. It might enable you to do faster perspective rendering like Driller because you could get better fill rates on the interiors of stippled surfaces by reusing a stippled tile. (Maybe Driller could have managed more than 1fps.) And Driller wouldn't have had to be black and white: four colors in a tile means that a tile containing an edge between two checkerboard stipples can contain four colors, two per checkerboard. 5. If you can change the base address register for the pattern table, maybe you can do it three times per screen during the HBI, thus clawing back the ability to treat the tiled screen as a full-screen raw framebuffer, without having to dedicate RAM to it all the time or losing the ability to scroll it rapidly. This might even enable you to cut the tilemap entries from 8 bits to 7—all you need for ASCII anyway—using the 8th bit for a half-brightness flag or something. Hindsight.

nottorp 5y ago

All that smart hardware and you end up with a device that can only run side scrollers and top down jrpgs, because that's what you can do with a tiled background and a few sprites. Could the NES run the first isometric games that showed up on the spectrum, for example? Or even some of the first primitive adventure games that used the built in graphics primitives to accompany the text with some graphics.

kragen 5y ago
The NES mostly couldn't, but it also had only 2K of RAM. The NES did end up with a quite faithful port of Marble Madness, but not until 01989, 5 years after the game's initial arcade release (which used a 68010!). The Spectrum port of Marble Madness was abominable, but that wasn't really the Spectrum's fault. However, the NES port did feature a full-screen viewport onto a smoothly-scrolling isometric playfield, which as far as I can tell no Spectrum game ever managed. (Maybe Golden Axe is closest?) I'm really interested in the question of how to use an NES-like tile engine to draw a 3-D world without perspective, like Fairlight, Knight Lore, half of Quazatron, Highway Encounter, The Great Escape, or Ant Attack—though remember that the Spectrum also had first-person shooters with perspective, like DeathChase, Tau Ceti, or 3D Starstrike, which maybe would have been harder to incorporate. I think there are at least four reasonable answers and one total cheat. 1. You can take an "oblique" rather than "isometric" approach, like Target Renegade, Golden Axe, and many old technical drawings. Your X-Y plane is the screen, and Z goes off at a diagonal, typically 45°. So your X vector is just [1 0], your Y vector is [0 -1], and your Z vector is, say, [1 -1]. Single tiles of surfaces in the X-Y plane are just single tiles on the screen, and that's adequate for when an X-Y surface occults a surface in any other orientation, as long as it's at a tile boundary. A tile of an X-Z (horizontal) surface becomes two right triangles, one in the lower right of a screen tile and one in the upper left of the tile to its right. Similarly, a tile of a Y-Z (vertical but not screen-parallel) surface becomes two right triangles, one in the upper left of a screen tile and one in the lower right of the tile above it. So, to make oblique renderings of axis-parallel arbitrary solid shapes out of a single X-Z texture, a single X-Y texture, and a single Y-Z texture (as in Ant Attack, though Ant Attack is isometric), all joined at tile boundaries, you need only 5 tiles: all X-Y, all X-Z, all Y-Z, and two that are half X-Z and half Y-Z. If you can have free-standing X-Z and Y-Z surfaces that occult an X-Y surface, like some of the walls in Highway Encounter, you need 4 more tiles: half X-Y and half either X-Z or Y-Z. An additional texture on the Y-Z plane costs you 3 additional tiles, or 5 with free-standing surfaces and arbitrary occultations. Similarly, non-straight edges, like in Where Time Stood Still, cost you an extra tile or two. 2. You can do "isometric" tiles with 45° angles instead of the correct 30° angles, so your X vector is [-1 -1], your Y vector is [0 -1] as before, and our Z vector is [1 -1]. This requires a larger variety of different tiles, has the same degree of geometric distortion, and might actually look worse: for a single texture on each plane you need not only the X-Y, Y-Z, X-Z, Y-Z/X-Z, and X-Z/Y-Z tiles from before, but also Y-Z\X-Z, X-Y/Y-Z, and 8 other combinations, 15 in all. 3. To do "isometric" with the correct 30° angles and only a little bit of geometric distortion, with your XYZ vectors being [-1 -½], [0 -1], and [1 -½], you can have four positions for a boundary within each tile: \ lower half, / lower half, \ upper half, and / upper half. This results in 27 tiles given one texture per plane, though not all will necessarily occur. The tradeoff for all this complexity is that now you have four colors per tile instead of two, possibly higher resolution, and faster screen updates, which enable a scrolling full-screen viewport. Note that, of the 3-D Spectrum games I mentioned above, only DeathChase, Knight Lore, and Fairlight have a nearly-full-screen viewport onto the playfield, and the latter two achieve it by having an almost totally static background with a 1–2-second "loading" pause in between rooms. By contrast, a tilemap would allow you to rapidly scroll a large viewport, as long as it was done in multiples of the tile size. 4. Instead of precomposing a pattern table that draws a full-screen "isometric" world, you can draw with total freedom into a small viewport by writing into the pattern table. (On the NES the pattern table was typically in ROM, but of course that would be impossible for a cartridgeless machine like the Spectrum.) This allows you to not only do partial occlusion effects and subpixel scrolling like The Great Escape but even perspective rendering like Driller and 3D Starstrike. It might enable you to do faster perspective rendering like Driller because you could get better fill rates on the interiors of stippled surfaces by reusing a stippled tile. (Maybe Driller could have managed more than 1fps.) And Driller wouldn't have had to be black and white: four colors in a tile means that a tile containing an edge between two checkerboard stipples can contain four colors, two per checkerboard. 5. If you can change the base address register for the pattern table, maybe you can do it three times per screen during the HBI, thus clawing back the ability to treat the tiled screen as a full-screen raw framebuffer, without having to dedicate RAM to it all the time or losing the ability to scroll it rapidly. This might even enable you to cut the tilemap entries from 8 bits to 7—all you need for ASCII anyway—using the 8th bit for a half-brightness flag or something. Hindsight.