Design and Implementation of a Video Game System: Rodent Revenge in Space Naoshin Haque Matthew Kwan Lynne Salameh 6.111: Introductory Digital Systems Laboratory December 9, 2004 Abstract: Rodent Revenge in Space is a video game, featuring Tim the beaver. Tim moves around the virtual world, where he encounters various enemies and obstacles. When facing an enemy, Tim throws logs at him. Tim will lose a life if an enemy injures him, but can gain lives by picking up powerups. The three modules in the game are the game controller unit, video controller unit, and the resizer. The game controller interfaces with the user and coordinates with the video controller unit to advance the game accordingly. The video controller unit outputs the images onto the screen and interfaces with the resizer in order to output the correct enemy size frame onto the screen. The resizer uses interpolation and decimation to shrink the enemy frame into different sizes. In conclusion, the project was a satisfying and extremely informative experience.Table of Contents 1 Video Game System Overview 1 2 Subsystem 1: Game Controller Unit (by Lynne Salameh) 6 2.1 PC Module 8 2.2 Instruction Decoder 10 2.3 Register FSM 15 2.4 Testing and Debugging 17 3 Subsystem 2: The Resizer (by Naoshin Haque) 19 3.1 Resizer System Overview 19 3.2 Resizer System Module Descriptions and Implementation 21 3.2a Major FSM 22 3.2b Minor FSM 25 3.2c Overall Resizer Module 31 3.3 Testing and Debugging 31 4 Subsystem 3: Video Controller Unit (by Matthew Kwan) 33 4.1 Video Controller Overview 33 4.2 Sprite_table Module 34 4.3 Sync_generator Module 35 4.4 Timing Controls 36 4.5 Line Register Module 38 4.6 Overview Module 39 4.7 Debugging and Testing 40 5 Conclusion 42 6 Appendix: Verilog Code 44 6.1 Game Controller Unit 44 6.1a Controller 44 6.1b Decoder 44 6.1c PC 53 6.1d Register File 54 6.2 Resizer 57 6.2a Major FSM 57 6.2b Minor FSM 59 6.2c Overall Resizer Module 76 6.2d Filter Coefficients 77 6.3 Video Controller Unit 78 6.3a 6bit Reg 78 6.3b Line Reg 78 6.3c Overall 79 6.3d Sprite Table 83 6.3e Sync Gen 88List of Figures Figure 1: Overall Block Diagram for Video Game System 5 Figure 2.1: Block Diagram for Game Controller 7 Figure 2.2: State Transition Diagram for PC FSM 10 Figure 2.3: State Transition Diagram for Instruction Decoder 14 Figure 2.4: State Transition Diagram for Register FSM 17 Figure 3.1: Overall Resizer Block Diagram 21 Figure 3.2: Major FSM State Transition Diagram 24 Figure 3.3: Minor FSM State Transition Diagram 28 Figure 3.4: Example Image Matrix 30 Figure 4.1: Video Controller Block Diagram 34 Figure 4.2: Sync_generator Timing Durations 36 Figure 4.3: Timing Interface between Game and Video Controller 37 List of Tables Table 1: Opcodes and Their Description 121 Video Game System Overview This project will consist of a video game named Rodent Revenge in Space. The main character, Tim the beaver, is lost in outer space. Tim is trying to find the wormhole, which will lead him back to MIT. Along the way, many aliens will try to stop Tim from completing his journey, because they want to use his intelligence to take over the universe. Tim can only counter the aliens by throwing deadly wooden stakes at them. Initially, Tim has three lives, but if he is injured by an alien, he loses a life. However, if Tim has less than three lives and he collects enough energy drinks, he can regain the lives he lost. The game will be configured so that the user’s perspective coincides with Tim’s perspective. The user will have access to six controls to manipulate the game: 1. Start button: initiates the game. If the user has pressed quit once, then pressing start would cancel the quit. 2. Up button: moves Tim forward through space. 3. Left Button: moves Tim sideways left across the screen 4. Right Button: moves Tim sideways right across the screen 5. Shoot Button: Triggers Tim to shoot a stake from where he is located on the screen The screen display will be divided into several frames, which will each have x, y, and z coordinates. The x and y coordinates denote the horizontal and vertical position of the frame on the screen, respectively. The z coordinate determines which frame will take precedence on the screen. The frames will be of the following description: 11. Tim’s frame: A frame containing a back view of Tim’s head. This frame will be positioned at the bottom of the screen, and will have the highest z value, meaning it will take the most precedence on screen. 2. Background frame: This frame is static, has the lowest z value, and consists of a space backdrop. 3. Road frames: There will only be one road frame on screen at a time, depending upon Tim’s forward motion. Each road frame will lie centrally in the screen and will have a higher z value than the background frame. 4. Enemy frames: These frames will move along the road frame and their size depends on the enemy’s distance from Tim. Their z value will be higher than the previous frames. 5. Log/bullet frames: The log/bullet frames will be moving along the road frame. These frames will have the second highest z value. 6. Energy frame: This frame will be moving with the road frame, but it will have a higher z value than the road frame. 7. Score/Lives frames: These frames will be at the top of the screen and will have a z value higher than that of the background frame. The game will be subdivided into three sections of roughly the same complexity: a game controller (Lynne), a decimator (Naoshin) and a video display module (Matt). A general block diagram for the system is shown below: Game Controller Unit: The game controller module handles the game’s logistics. The game controller is in fact an FSM which has various states depending on the inputs. The game controller’s 2main job is to decide which frames are going to be used in the video display at each time-slice. The time-slice’s value will be chosen to simulate the game smoothly. The game controller will have an algorithm which decides when the alien will come on screen, and its trajectory towards Tim. The information associated
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