6.170 Laboratory in Software Engineering
Spring 2004
Final Project Amendment: Poly-Gizmos

Handout F5

Contents:

Background

The staff members in charge of acceptance testing have enjoyed using your initial implementation. We have decided, however, that the pinball game needs to be extended. First, we want to be able to create boards with multiple balls since we are unchallenged by only a single ball on the board. Second, we would like to be able to create bumper gizmos with arbitrary polgygonal shape that the ball can interact with.

You must extend Gizmoball to support arbitrary polygonal bumpers and multiple balls.

Multiple Balls

You must now support multiple balls. This requires no change to the file format, except that there can be multiple "Ball" commands each correponding to a new, different ball. In build mode, you must allow the user to place multiple balls on the board, and in run mode these balls must realistically interact. The behavior of the absorber is now underspecified. You will need to specify absorber behavior when multiple balls interact with an absorber and write this up in your final write-up.

Note: We are allowing you to maintain a default (and unmodifiable) size and mass for each ball that is placed on the board; you therefore do NOT need to support arbitrary ball sizes and densities. If you choose to support larger balls, however, make sure to make a (reasonable) modification to absorber behavior.

Poly-Gizmos

Your Gizmoball game must now support static bumpers with arbitrary polygonal shape. The ball will interact with these "Poly-Gizmos" just like the triangular, square, and circular bumpers. You will be required to load Poly-Gizmos from XML files, but you are NOT required to provide GUI support for creating arbitrary Poly-Gizmos (though we encourage you to think about how to do so and make an attempt if you have time!)

File Format

In order to create and place Poly-Gizmos, a new element has been added to the provided XML schema. Here is a sample file using the new polyGizmo element and polyGizmoVertex sub-elements: 
<board>
 <gizmos>
  <!-- define an OCTAGON! :-) -->
  <polyGizmo name="PG13" x="1" y="2" width="3" height="3">
   <!-- vertex locations are RELATIVE to polyGizmo x,y -->
   <gizmoVertex x="1" y="0"/>
   <gizmoVertex x="2" y="0"/>
   <gizmoVertex x="3" y="1"/>
   <gizmoVertex x="3" y="2"/>
   <gizmoVertex x="2" y="3"/>
   <gizmoVertex x="1" y="3"/>
   <gizmoVertex x="0" y="2"/>
   <gizmoVertex x="0" y="1"/>
  </polyGizmo>
 </gizmos>
</board>

The format of the element is similar to the squareBumper and circleBumper elements: 

<polyGizmo name="STRING" x="INTEGER" y="INTEGER" width="INTEGER" height="INTEGER" />
<gizmoVertex x="INTEGER" y="INTEGER"/>

If you would like to use an updated schema (with references to polyGizmo and gizmoVertex), you can find it here.

Sample Boards

We provide a sample board (given in the standard file format) to illustrate one of the many possible configurations your clients expect to be able to create and play using these new features.

Ambiguities

Parts of this amendment have been left intentionally vague. It is up to you to decide what (if any) clarifications are necessary. You should include any changes to your Revised Specification documentation in your final submission on 5/11/2004.

Design Decisions

Spend some time thinking about the best way to incorporate this change into your design. In your final design write-up, be sure to discuss the changes to your initial design (and the relevant trade-offs). You will be graded on how easily your initial design can support the amendment, and how cleanly you incorporate the amendment into your design.

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