The Animation of Phoenix, Part 2: Birds in Flight



Previously, I demonstrated the animation that was used to bring the birds of Phoenix (1980) to life.  Now, I want to take a closer look at their movements.

Paths of the Large Fliers

An animation from the third round of the 1980 arcade game, Phoenix, showing the motion of a group of large birds..

The motions of the large fliers are not very complex, but can still be difficult to predict.  Their vertical motion proceeds entirely in unison, allowing them to keep a formation of sorts, but fluctuates up-and-down in an unpredictable way.  When allowed to fly unmolested, their motions appear like undulating waves and can even wrap around the bottom of the screen.

The horizontal motion is oscillatory, and despite starting out in unison, eventually goes out of sync due to random fluctuations.  They can go partially off of the edges of the screen, but don't wrap around.

Paths of the Small Fliers

An animation from the first round of the 1980 arcade game, Phoenix, showing the motions of the small birds.

The small fliers, with their aerial gymnastics and complex animations, are really the backbone of the Phoenix experience.  Watching clips of the game's first two rounds, you almost get the feeling that these birds have a life of their own, juking and jiving across the screen like choreographed dancers.  But how did the designers create this spectacle?  

Sprite Tracking

One of my favorite toys, which I've been developing for some time now, is the sprite tracker.  With this interactive Python script, I can match sprites that I've extracted to images taken during gameplay, and then trace their path across the screen.  My first trials were on the aliens in Galaxian (1979), with the results shown below.

An animation showing the paths of the three colors of galaxians in the 1979 arcade game.

The three colors of aliens each follow their own distinct path, starting with a semicircle when they leave formation and finishing in a sweeping arc.  Each alien arcs differently to end its dive, with the purple alien arcing so sharply that it almost returns to the horizontal position it started from.

The paths in Phoenix are much more complex than those in Galaxian.  In order to simplify the problem, I eliminated all but one of the birds and then tracked its motion.

An animation from the first round of the 1980 arcade game, Phoenix, showing the path of a small bird.

My first thought was... well, that didn't help much.  It just looks like a preschooler's art project, but then I started breaking it down into smaller chunks.  Here are some of the patterns I found in the first round:

An animation showing some of the paths traced out by the small birds in the 1980 arcade game, Phoenix.

As it turns out, the fliers actually follow repeatable closed loops.  They start by flapping slowly left-to-right or right-to-left.  Then they dive, trace out the pattern, and return to their slow-flapping state in the same location.  By returning to their previous location after a dive, the fliers are able to return to formation, something that is more apparent when they're in large groups (see the animation in the previous section).

Here are some of the patterns I found in the second round:

An animation showing some of the paths traced out by the small birds in the 1980 arcade game, Phoenix.

These patterns are not created randomly, but are predesigned and repeated in what appears to be a random order.  Their complexity is such that even an experienced player would have difficulty predicting the bird's motion.  This lack of predictability, in combination with the many-framed animation, help give the small fliers an appearance of life.  This is starkly different to the minimalist approach taken by Galaxian, where the motions of the enemies were so simple that they behaved like mindless drones.

In the final installment of my deep dive into the animation of Phoenix, I'll talk about the way they made use of double-tilemaps to create the elaborate animations, and how it would have been different with sprites.

Comments

  1. A stunning entry! It’s like deciphering secret messages.

    Also, most of them look like race tracks which matches nicely (albeit not on purpose) with the car/spaceship you steer.

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