Line scrolling functions the same as row scrolling, but each horizontal scanline is able to be scrolled independently rather than each 8-pixel row. Developers got truly creative with line scrolling, and some of the console’s most impressive effects are done using it.
Let’s look at an example from the opening stage of Thunder Force IV:
There is perhaps no better example of parallax on the Mega Drive. The top of the screen shows layers of clouds (discussed previously). However, as the screen scrolls to the bottom, we see that the water is done with line scrolling. Each line of the water is scrolling at a different rate, with the lines closer to the bottom scrolling faster, giving a strong impression of depth:
Fighting games typically use line scrolling for their floors to create this sense of depth. This is most noticeable when the floors have a checkerboard or grid pattern:
Here are the two 64 x 32-tile planes:
Of course, the technique is not limited to fighting games:
This boss fight from Dynamite Headdy really goes all-out with the concept:
Here we have the illusion of a giant donut-shaped platform with the boss in the middle. The checkered floor under the player scrolls per-line, while the opposite side of the donut scrolls as a section in the reverse direction. The near foreground shows the wooden supports holding the floor up, scrolling as one section and giving a sense of height to the platform.
All of the scrolling occurs on Plane A, aside from the golden pillar that passes in front, which is on Plane B. Here is a breakdown of each plane and the sprites:
The scene gets even more impressive when the giant boss grabs onto the platform and spins it around:
We’ll look at how the boss itself moves in a later section, but the point here is that the line scrolling is used very effectively to create the sense that the platform is rotating.
Ranger-X is particularly famous for its impressive effects. Look at the line scrolling in this example:
The sense of depth of the tunnels is well-realized. How is it done? The effect becomes clearer if we remove Plane A:
Line scrolling is being applied to the floor and ceiling of the tunnels, while the walls are simply a solid two-tone color that doesn’t give a sense of depth alone (but our brains apply depth to it due to its surroundings). Plane B is on a very short scrolling loop, so the back of one tunnel never appears visible on the side of its neighbor tunnel.
Here’s another interesting line scrolling effect from Ranger-X, creating the impression of traveling through a cylindrical passage:
The near plane appears convex from the perspective of the viewer since it scrolls fastest towards its center, while the far plane appears concave since it scrolls slowest towards its center. The result is visually impressive but done using the same line scrolling technique.
Battle Mania 2 has a similar effect, but this time the cylindrical passage appears to be rotating:
For this effect, each plane is being scrolled both horizontally and vertically. Line scrolling is used to create a sense of curvature by shifting the scanlines horizontally more and more as they near the top and bottom of the screen.
Line scrolling is often used with sine wave patterns to create unique effects. The lava on this stage of Twinkle Tale appears to flow back and forth:
Using sine wave patterns is a popular technique for screen transitions, as seen in M.U.S.H.A.:
Ranger-X creates a wonderful line-scroll-driven water ripple effect in this scene:
When the player moves in the water, the scanlines began to wobble back and forth. The intensity of the sine wave driving the movement is higher towards the bottom of the screen where the player is standing. If the player remains stationary, the effect begins to diminish in intensity.
List of Effects:
- Full-Screen Scrolling
- Row / Column Scrolling
- Line Scrolling
- Multi-Jointed Characters
- Tilting / Rotation
- Shadow and Highlight
- Palette Swapping
- Vertical Scaling
- Sprite Raster Effects
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