Computer Graphics Final Write-up
The SpeedRacer game is made up of eight classes, and three nested
classes for event handling in the 1.1 JDK:
Selected object message passing.
- class SpeedRacer
- This is the main class which extends Applet and creates three panels
on the screen for drawing: the SkyCanvas, the DashCanvas, and the
- class SkyCanvas
- Above the horizon is the sky, which is currently drawn blue once,
and is never repainted unless that part of the applet is exposed by
- class DashCanvas
- This canvas shows the car's current speed (in the units of your
choice), amount of damage sustained from hitting barriers (shown as
a percentage bar), number of good guys (wearing red) and bad guys
(wearing black and wielding guns) killed, total score, and time left.
- class RoadCanvas
- This is the workhorse class for the entire game, since it is
responsible for drawing the bulk of the graphics and determining
collisions between the car and Targets. First, it creates the Targets
that will appear in the road. Following this, it creates the Ticker
thread, that will periodically request that the game state be updated.
See below for a description of the Ticker/RoadCanvas interaction.
- class Target
- Contains and is responsible for loading images for each item that
you careen toward on the road. It can load two images and cycle between
them at a given interval, if so desired. It also can move an image
across the road at a given rate when its update() method is called.
(This is how the people appear to "walk".) It also resets the location
of the Target to the top of the screen at a random X position if it
rolls off the bottom. One more image that it keeps track of: the dead
image. This is the image that is displayed after the Target has been
hit by the car.
- class Car, class Line (not shown in diagram)
- These are two simple "struct-only" classes that hold information
about the Car's position and score, and the position of the lines in the
The ticker sleeps for a short amount of time (20 milliseconds), then
calls the "tick()" method in its parent, then repeats the process. In
this case the parent is the RoadCanvas, and it performs a variety of
tasks in the tick() method, including:
- Call each Target's update() method to move them down and across the
- Move the Lines down the screen.
- Perform some checking to see if the car is "in the air". When the
car collides with a target, it is bumped up a little bit. This
particular check will lower the car back toward the ground, so that it
experiences a little bump when it hits things.
- Accelerate the car toward the mouse.
- Update the stats in the DashCanvas.
- Perform rectangular collision checking with the Targets, and perform
the necessary actions.
- Check for game over due to timeout or damage.
- Schedule a repaint of the RoadCanvas and of the DashCanvas.
Some improvements that could be made to the game are:
- There is no sound currently. I was hoping to make some
cheesy sound effects, but my sound editor kept crashing. (I guess my
home-made sounds were just that bad.)
- The images aren't drawn in the correct z-order. Since they tend to
not collide with each other that often, this isn't usually seen. It
does happen, though.
- The car should bounce and slow down if driven off the road.
- I wanted to have the "Game Over" text zoom in from the distance. I
also want a "Speed Racer" intro screen of sorts.
- The lines tend to get bunched together as the game progresses.
While I haven't tracked down this bug, I suspect it has to do with the
car accelerating while some lines are closer to the bottom of the screen
than others. A fix seems ugly, but not impossible.