Overview

CSC 481/581 Fall 22 Homework 3 Due: 10/26/2022 by the start of class

Your task for this assignment is to add more functionality to your engine. You will submit your code and a writeup of your results, including screenshots where appropriate. This is an individual assignment, you are to work alone. As always, you are expected to abide by the University’s Academic Integrity Policy (http://policies.ncsu.edu/policy/pol-11-35-01), which includes providing appropriate attribution for all external sources of information consulted while working on this assignment.

There are 125 points available on this assignment. Students enrolled in 481 are required to complete the first 100 points (Sections 1–2), but may also choose to complete Section 3. Students enrolled in 481 earning scores above 100 will receive a 100 on the assignment (i.e., extra points will not be given as extra credit). Students enrolled in 581 are required to complete all 125 points, and will receive a grade as the percentage of the 125 points they earn. All students are required to submit a writeup addressing the sections of the assignment they have completed—simply submitting code without a writeup discussing that code or including a section in the writeup to cover a part of the assignment for which there is no code submitted will result in zero points for that section of the assignment.

This assignment is worth 20% of your homework grade. All scores will be converted to be out of 20.

Given issues that arose with Homework 2, the standard grading environment will now include three additional apt packages: nlohmann-json-dev, libzmq3-dev, and libzmqpp-dev. In other words, you may additionallyrunsudo apt install nlohmann-json-dev libzmq3-dev libzmqpp-devin your grading environment.

Part 1: Game Object Model (70pts)

For the first component of this assignment, you must design and implement a runtime game object model of your choosing. The design is completely up to you. You may opt to use one of the models covered in lecture, or come up with something on your own. The main requirements are that it be extensible enough that you can reasonably implement new types of objects that you aren’t necessarily using at this point in time and that you motivate and defend your design in your writeup.

To demonstrate your model, you must implement a 2D platformer with at least the following objects:

1. Characters that are the depiction of the client-controlled players. Characters must respond to key-

board inputs to move left and right, as well as jump.

2. Static platforms (i.e., rectangles) that have a position in the environment and a color. Demonstrate at least three different colors by creating at least three different platform objects.

3. Moving platforms that are implemented similarly to the static platforms, but also move around the screen in a patterned way. Demonstrate at least two different patterns of movement.

4. Spawn points that are hidden (i.e., not drawn or rendered to the screen) objects marking the location where characters start from. There may be multiple spawn points in your environment.

5. A “death zone,” which is a different type of hidden object that marks some boundary of your en- vironment. When a character collides with the death zone, they should be teleported a spawn point of your choosing. There may be multiple death zones. You must use collision detection in order to demonstrate the death zone in use.

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6. A “side boundary,” which is another type of hidden object similar to a death zone, however when a character collides with a side boundary it should trigger a lateral translation of all objects in the scene (some of which may transition from viewable on the screen to not, and vice versa). This is the mechanism by which you must implement side-scrolling.

When implementing these game objects, think in terms of the game object model you developed. Are you using inheritance to accomplish different behaviors? Components? Properties? What behaviors, properties, or components do you need to get these game objects working right?

Although not required, it may be very informative to implement additional functionality like scoring, a goal location, and/or a timer.

Part 2: Multithreaded, Networked Scene (30pts)

For this portion of the assignment, your task is to fully integrate your SFML codebase with your mul- tithreaded, networked client and server from Assignment 2. If you are enrolled in 581, this should be integrated with your code from Part 5 of Assignment 2. If you are enrolled in 481 you may choose to in- tegrate with either Part 4 or Part 5 from Assignment 2. At the minimum, you must support the following functionality:

1. Youmusthaveamultithreadedserverthatreadsdatafromandsendsdatatoclients,allwhileaccepting an arbitrary number of incoming connections at arbitrary times. Whether you send GameObjects, Strings, primitive types, or something else isn’t critical provided the correct behavior results.

2. You must handle keyboard inputs that control the movement of a unique character object on each client.

3. You must draw the entire scene on as many as four clients, including the movement of objects con- trolled by the inputs on the clients.

4. You must utilize your runtime object model on both the client and the sever.

5. You must gracefully handle client disconnects, where one or more clients may disconnect at any time and the remaining client(s) and the server will continue normal operation, without the representation of the disconnected client(s) player objects being displayed.

In other words, you should start a server which will define the “scene,” i.e., maintain the game world object model including static and moving object locations. Then, you should start any number of clients (we will test with up to four simultaneous clients, although may connect and disconnect several clients before reaching four), where each client connection will generate a new player character object and handle keyboard inputs to move that object around the scene. Each of those inputs or movements (depending on your design) should get transmitted to the server, where it will be re-sent to every other client and drawn on their scenes as well.

The main differences between this part of the assignment and Part 3 of Assignment 2 are: 1) You have a requirement to handle an arbitrary number of connections that initiate at arbitrary times; 2) You have a requirement to handle graceful disconnects when clients stop; and 3) You have a requirement to implement all of this using the runtime game object model from Part 1 of this assignment. As a reminder, each client should run in a separate process, not a thread within a single process.

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Part 3 (required for 581, optional for 481): Performance Comparison (25pts)

For this section of the homework you will implement a second “network data exchange format” and do a performance comparison. Your aim for this part of the assignment is to characterize the performance of different approaches to client/server communications. You are to continue to use 0MQ as the library to fa- cilitate communications; however, you must devise at least two different strategies for sending information between the clients and the server. Practically, this means either keeping the representation (e.g., packed strings) the same and varying the type of information sent (position updates only, or entire object repre- sentations), varying the representation and keeping the information constant, or changing the ZMQ socket types substantively (e.g., to make it peer to peer). The goal is to have the differences between your two approaches be different enough that there is a noticeable performance difference, but not so different as to fundamentally alter the “game play experience.”

To compare your two methods, you must use a server with two, and in separate set of experiments three clients (although you may find it informative to do more). You will want to measure the performance in terms of runtime. Given that you’re using a fixed number of clients (two and three), you should change the number of static and moving objects in the environment. The moving objects do not have to be controlled by keyboard inputs. You will want to measure how long it takes to complete some number of game loop iterations (say 100,000) under different conditions. How long does it take with 10 moving objects on each client? What about 100? Can you get to 500? How does this change if you’re using two vs. three clients?

Note: It is not required that the code for this part of the assignment be integrated with your platformer game. You may choose to branch your codebase to develop a stand-alone application to collect your data and analyze performance, but it is required that you are using your runtime object model. It is also expected you will collect, analyze, and visualize (i.e., graph) data from these experiments to support your conclusions.

Writeup

Now that you have designed and implemented a number of engine components, write a 2-–3 page paper summarizing your design. That is a minimum of 2 FULL single-spaced pages. It is strongly suggested that you do not limit yourself to only answering the questions posed in this assignment. Think creatively about what you have done. Why did you make the design decisions you made? What did they enable for this assignment? What will they enable in the future? The most successful writeups will contain evidence that you have thought deeply about these decisions and implementations and what they can produce and have gone beyond what is written in the assignment.

As an appendix to your paper, please include all relevant screenshots to support your discussion. The appendix does not count toward your 2—3 page requirement. For students completing Part 3 of the as- signment, any graphs used to present data should be part of the appendix. Your points for the writeup will represent 12 of the points allocation for each of the above sections (i.e., 35 of the 70 points for the “Game Object Model” section will come from your writeup).

What to Submit

By the start of class on 10/26/2022, please upload to moodle a .zip file containing your code, a README file with compilation instructions and execution instructions, and a .pdf of your writeup.

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