Posts Tagged pixel

A Layman’s Guide To Projection in Videogames

Oftentimes when a videogame has a skewed, overhead point of view, we call it isometric. That’s rarely the accurate term, though, and it’s not just pointless semantics.

echochrome

Although Echochrome uses a single projection type, its gameplay is based on constantly rotating and morphing its 3D structures. With each new view, the physical architecture of the level changes to reflect what the player sees on the screen.

Projection basically means taking a three dimensional object and displaying it on a 2D plane (i.e., a screen). There are various ways of accomplishing this, and each technique has a deep impact on a game’s look and mechanics. The advent of 3D games and free-floating cameras somewhat lessened this role, but being aware of the pros and cons of each projection type is still applicable to both 2D and 3D titles.

So what exactly are these projection types? Well, let’s take a look:

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The 1-Pixel Collision Box

In the early 90s, a trend developed among shoot-’em-ups that was affectionately (or was it rancorously?) dubbed “bullet hell.”

touhou10fs4

An example of bullet hell. It gets worse. Much worse.

The impetus behind it was to add visual flair to 2D games in order to compete with the craze surrounding 3D games. Arcade cabinets were more powerful than ever before, so these shooters could handle many more sprites and the extra calculations required for the accompanying collision checks. The approach worked relatively well, providing plenty of “Holy Shit!” moments. However, there was one major issue: playability.

ikaruga2

Ikaruga's dual colour scheme was the focus of its gameplay.

Shoot-’em-ups tended to be one-hit kill games, and simply saturating the screen with harmful projectiles made them incredibly difficult (if not downright impossible). Now arcade games are meant to take your money, but that wouldn’t happen if no one played ’em. In order to implement bullet hell without alienating customers, something had to give.

Part of Ikaruga‘s solution was to make all bullets and your ship one of two colours, and then simply ignore collisions between like-coloured objects. Other titles used shields and various powerups, but the original solution, and, in a way, the purest to the genre, was the (roughly) 1-pixel collision box.

Instead of surrounding the majority of the player’s ship with an area susceptible to fire, a single pixel was used to indicate its vulnerable spot. This was a rather elegant solution as it required no other changes and didn’t present an extra hit to performance. Players were also less likely to feel cheated if they came out on the positive end of some collision-fiddling. The end result looked something like this:

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Saint Dragon's eponymous lead actually looked pretty good in motion.

The visual oddity of having the player’s ship fly straight through harmful projectiles was lessened by the nature of the top-down perspective. This view had issues with representing depth/elevation, and that actually made it easier to imagine bullets just skimming over the player’s ship. The 1-pixel collision box also had the side-effect of making the player feel more skilled at the game, which — in the very least — provided the illusion of empowerment.

As a side note, something of a similar concept was used in an old Amiga shooter called Saint Dragon. The player’s ship, the eponymous Saint Dragon, consisted of a head and spiraling tail. The head used regular collision detection, but the tail was purely aesthetic. This added scale and personality, and allowed the player to control a vehicle that seemed grandiose despite being virtually identical to countless other shoot-’em-up ships. The head could be easily destroyed, but the tail would actually absorb many types of bullets and even damage most of the enemies it touched.

Supplemental:

Since I’ve posted this article, it’s gotten a lot of attention from numerous shmup enthusiasts. Many have been eager to bring up the specifics of the tiny-collision-box phenomenon, as well as variations on the theme. I think that’s great, and one of the sites that has been pointed out to me contains a lot of interesting information on the genre. Of particular note are its threads on shmup strategies, the dos and don’ts of good shmups, and the glossary of common shmup terms.

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