Asteroids

Introduction

Implementation Strategy

• First I took on the task of creating objects and animating them.  In order to do this, I was forced to learn the add_timer function from the FLTK library.  With this function, I could force a redraw of my scenario 30 times per second, effectively making smooth motion.  I began with only 3D color cubes for simplicity.  Each asteroid rotates randomly, begins with a random start point, and translates in an arbitrary linear manner.
• The second step that I took was to add in the player's ship.  This was simply a matter of drawing something myself and inserting it into the scene.  No big deal.  Once it was inserted, I defined the arrow keys to make the player move and rotate.
• Next I began the task of collision detection.  I used the bounding box method as suggested by Professor Pang to determine when things would collide.  Once two unalike objects shared a coordinate space, I printed out a message to standard output.
• With collision detection working, I enabled the player to fire from their ship.  The space bar was used for this task, and the shots followed a trajectory determined by the rotation value of the player's ship.  At first I simply used a pixel to represent the player's munitions.  I incorporated collision detection in with the shots fired as well.
• Once these basic steps were functional, I made the asteroids shrink in size once they were collided with.  The asteroids start out large and can be shrunk two times before being ultimately destroyed.  Once destroyed, they simply were not drawn anymore and a flag was set for that asteroid so that the player's ship would not be destroyed by something that was not there.
• In an effort to add more of a game-like feel, I added the concept of lives and points.  Though not obvious in any way, the player starts out with 3 lives, which are depleted one by one whenever they are collided with.  Once all of the player's lives are gone, they are given the option through standard input to play again.  The standard out/in part of this feature is very annoying and I did not have time to make something more eloquent.  The points are maintained through a little output box in the lower left hand corner.  This was necessary so that I could compete with my friends.
• Next I decided that the player needed to cruise around in style, so I inserted the Starship Enterprise.  This was a more difficult task than I had originally anticipated as many things needed to be scaled down or up to accomodate the large new object on the screen.  Collison detection became a slightly more difficult task at this point as well.
• I then improved the look of the player's bullets.  I created a 3 dimensional object out of 8 triangles, sort of like a double sided pyramid.  This object is colored red for easy visibility.  I also designed a trail of pixels to follow behind the player's shots and make things look cool.  The pixels can only travel a short distance from the rear of the player's shot and are in many different colors.
• From here, I created (with the help of Jonathan Cheatham) a texture map for my asteroids to give them more of a rustic dirt look.  I applied this texture map to each side of the asteroids and that made them seem a bit more authentic.
• Finally, I engineered a sort of explosion which occurs whenever the ship or asteroid is destroyed.  Though not perfected, it is still effective and serves its purpose.  When an asteroid is shot, a field of small pixels erupt from that point and expand outward for a second.  When the player's ship is collided with, a larger explosion with bigger pixels is generated.

How to Play

>asteroids

From there, the user will be prompted to enter a seed for the random number generator used so heavily in this program.  This was absolutely necessary so that you don't play the same configuration every time.

Up Arrow - moves the player in the direction they are facing

Down Arrow - applies reverse thrusters and moves the player in the opposite direction that they are facing

Right Arrow - rotates the player clockwise (I think)

Left Arrow - opposite of the right arrow

Space Bar - fire phazers

Comments

wildone@cats.ucsc.edu