Musings on computer-rotated sprites in old-school games

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Musings on computer-rotated sprites in old-school games

Post by Expack3 » Fri Oct 19, 2012 3:31 pm

I've been having some rather intriguing daydreams about "What If?" scenarios - not of the 'fanboy/girl', mind you, but of the realistic type - of whether it might've been possible to save some disk space on the older Sierra games by having rotating sprites, like wheels and people (Roger Wilco, I'm looking at you!), actually rotate instead of being animated by hand. If this were possible back in 1989-1995 using nothing but CPUs and memory, it might have lead to some more interesting scenes in adventure games. For example, you could have the villains, whose faces are obscured by the overhead angle of the camera, are shown plotting out their latest scheme on a table using various supplies. Accompanying the music, the entire room, which would effectively be one large, animated image, is rotated at a tense pace to add to the suspense, cutting in with pseudo-rotating scenes of the villains at a normal perspective.

Of course, such a method would have some limiting factors:
  • A smoothly-rotating sprite whose rotation calculations are rendered on the CPU wouldn't have the benefits of bi-linear or tri-linear filtering, resulting in a rather jagged, pixelated-looking image during parts of the rotation process.
  • While, at the very least, bi-linear filtering could be achieved via CPU rendering as well, would that even be feasible in the early-to-mid 90's?
  • Technically, with the rise of 3D accelerators, you could get bi-linear filtering by putting the sprite on a planar polygon and have the 3D accelerator rotate the polygon, thus simultaneously achieving a rotating sprite as well. However, to my knowledge, such a feature would only be available on more advanced - and, thus, more expensive - 3D accelerators.
  • Depending on the angle and perspective the rotating sprite would need to be viewed in, it may prove more troublesome than any space savings since you'd still need an animated portion to give a convincing illusion of a rotating object. In fact, for some sprites, like people, perspective could force the sprite to be hand-animated anyways in order to achieve the illusion of rotation.
  • How hard would it be to code rotating sprites in the early-to-mid 90's on MS-DOS machines? Would the increased processing requirements and the space savings - if any - be worth what could be gained?
While I don't know if it would be feasible, let alone possible, I just think it might be a cool idea.
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