Lesson 7: AnimationOkay, time to breathe a little life into these backgrounds for that finishing touch!
Here's the full tileset including animation alternates. I'll be referring back to it as I go through the various animation types.
The essence of animation is visible change, obviously. If you think back to the very first part of this series each tile is influenced by two sources of information, the palette (what colors are available) and the pattern table (which colors go where). Thus, any change to either of these two items will cause a visual difference in how the tile is displayed on screen. Of the two, changing the palette is far less taxing on the system so most games use this for the vast majority of animation effects.
The simplest change we could make is just to change one color, and this is exactly what we're going to do animate the lights in our deepest backgrounds. when that one color on the palette changes every tile using it will update simultaneously (or at least as fast as the tv/monitor's scan rate can manage) to the new color choice. In this case we want a simple pulsing animation for the lights on both our dark blue interiors and the underwater... things... which we will accomplish in a 4-step cycle. We just set it up to rotate in stages through pale yellow, light orange, dark orange, and then light orange again (light green/royal green/aqua/royal green for the underwater things). When put on repeat this produces a fairly smooth loop with a soft pulsing.
Another very common effect we'll be making use of is cycling multiple palette colors at the same time, specifically just juggling the same three in sequence to create flowing water effects. By changing them systematically in the order darkest > lightest > middle > darkest we can create a sense of movement even though the patterns stay perfectly still because the eye wants to follow the highest contrast area (where darkest and lightest touch) which will be shifting.
There are plenty of other ways this can be used that we won't be needing for this stage by combining these effects that we won't be using for this map, but which can easily be seen at work in MM2, for example. Take Airman's stage, those fluffy clouds gently puffing in and out; what's actually happening there is that the two darker edges of the cloud are being palette cycled progressively towards white and then back to create that effect, essentially a more subtle version of the lights earlier but using two colors for the effect rather than just one. The gears and pistons churning away in Metal Man's stage are actually using a similar technique to the water animation, specifically there's one color stuck on brown, the black background, and then the last two colors are flicking back and forth between brown and black (basically on or off) to create the illusion of movement. The same technique is used in the 'screens' on Dr. Wily teleporter room, though in that case they cycle between through 1 on > 2 on > both on > both off > repeat.
Here, see for yourself. Aside from highlighting the different pallette colors in the metal sample these tiles are straight from the game.
When things get more complicated however we need to consider changing the pattern tables rather than just the pallettes. This type of animation is used very sparingly in NES games because it's much harder on the processor and is likely to produce lag, but some later games made use of it more freely due to additional help from various special chips built into the cartridges.
In this case, we need a little more effort to make the propellers look convincing. Just flipping the propeller vertically is a good start, but it still needs another frame to sell the movement otherwise it just looks like it's twitching back and forth rather than spinning. One more frame, with two 'forward' blades about halfway between the two and a vague shadow for the blades that would be coming around further back, makes for a surprisingly smooth animation with just 3 frames total on a cycle.
These sorts of effects are always saved for impressive details and usually used sparingly. The GB games tend to indulge in these more often since otherwise animation would be impossible as there's only one pallette to work with, but otherwise the megaman series doesn't use the technique very often. For more extensive examples I'd point you to Natsume's
Shatterhand (check out those fans and water effects) or Sunsoft's
Batman: Return of the Joker, or the extremely impressive use Irem's
Metal Storm makes of it for pseudo-parallax effects.
Of course there's one more type of animation involving background tiles that no Megaman-based discussion would be complete without... the large boss or miniboss. There are hardware limitations which limit the maximum size a sprite can be, but by combining a mobile background with a few sprites above it for action and extra colors some fairly impressive enemies can be created. The miniboss of the stage isn't that big in X3, but it's still a good opportunity to play it up for the true NES experience. To pull this off you need a large area with no tiles so that background scrolling can be used to move the miniboss without interrupting the rest of the screen, then a few well-placed sprites to round it out. You do need to take some care not to use too many of them and to space them out vertically as too many sprites on one horizontal line cause flickering.
Finally, here's a few screenshots I mocked up from the stage map with the animation fully implemented so you can see it in action:
Next time: MM8BDM conversion
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I think I'll have to break that down a little bit.
