Page 2. Microsoft XNA's Game Loops w/ Text Animation
Last updated
Last updated
The goal of this project is to introduce the concept of game loops in Microsoft XNA by creating a simple text animation that changes color and position. It will also teach the concept of clamping to ensure the text stays within the bounds of the window.
Before you jump into the project, it's essential to make sure you've got the basics covered. If you're entirely new to Microsoft XNA and MonoGame, it's recommended to start with an introductory project. Please follow the walkthrough provided on.
List of Prerequisites:
A working installation of Visual Studio
MonoGame framework installed
.xnb of your desired font (Review Page 1 to make one)
Once your new project is set up, go to the Game1.cs
file. Remove all the code there, and we're going to build it up step by step for this text animation game.
Before writing any code, import these key libraries:
Microsoft.Xna.Framework: This is the core library for XNA game development.
Microsoft.Xna.Framework.Graphics: This library is used for all graphical operations.
Microsoft.Xna.Framework.Input: This library lets you handle user input like keyboard and mouse events.
What are libraries
A library is a collection of pre-written code that you can include in your programs. Libraries are important because they speed up development, offer optimized functions, and allow you to focus on the unique aspects of your project. However, using them might limit customization and introduce dependencies. They are tools to make your coding more efficient, but they're not always the ideal solution for every project.
Before we even dive into the Game1
class, let's talk about a line of code that acts like the address of your 'coding house'. Yep, it's the namespace
.
Namespace: Think of a namespace as a folder on your computer. It organizes your code files, helping to prevent naming conflicts.
GameLoops: This is the name of your specific folder. You can choose any name, but it should be unique to avoid confusion. It helps the compiler know where to find your specific classes and methods.
Now, let's nest our Game1
class safely inside our namespace, giving it its full address.
By putting the Game1
class inside the GameLoops
namespace, we're essentially saying, "Hey, Game1 lives at the GameLoops address!" Make sure you put all your related classes in this same 'house' to make your life easier when you're coding.
GraphicsDeviceManager graphics: Manages screen drawing
SpriteBatch spriteBatch: Draws 2D images
SpriteFont font: Sets the text style
Vector2 position: X, Y coordinates for text
Vector2 velocity: Speed and direction of text
Color color: Text color
public Game1()
is where you initialize these components
This is where we set up our stage, placing all the props and making sure the lighting is just right.
PreferredBackBufferWidth & PreferredBackBufferHeight: This is where you adjust the window dimensions.
ApplyChanges: This makes sure changes take effect
position = new Vector2(400, 300);
: Here, we're setting the initial x and y coordinates for our text on the screen. Think of Vector2
as a way to store two related numbers—in this case, the horizontal (x) and vertical (y) position of the text.
velocity = new Vector2(2, 1);
: This vector represents the speed and direction of your text's movement. The x-value "2" makes the text move to the right, while the y-value "1" makes it move downwards.
Here you load all the content you need for the scene. Backgrounds, characters, and fonts all get picked up here.
spriteBatch: This is responsible for drawing 2D images on the screen.
font: This specifies the style and size of the text that will appear on the screen.
This is where you direct the action scene by scene, directing objects where to move and what to do.
Let's break down each line:
MathHelper.Clamp()
: The Clamp function restricts a value to lie within a specified range. It's a way to ensure the text stays within the screen's bounds. If position.X
goes below 0, it will be set to 0; if it goes above graphics.PreferredBackBufferWidth - 100
, it gets set back to that value
color.G += 1;
: Here, you're incrementing the Green (G) component of the text color by 1 in each frame. Color values range from 0-255, which leads to the next line
if (color.G > 255) color.G = 0;
: This resets the green component back to 0 if it goes over 255, creating a loop of color changes.
Finally, it's time for the actors to perform! This is where all your plans come to life on the stage.
I hope this clarifies the process and adds some fun to the coding process!
Here's the full code for the project:
Update the Update() function so that when the text reaches the border of the screen, it bounces in an opposite direction
The changes are in the conditionals that detect when the text is about to exit the screen. The velocity is reversed (multiplied by -1
) and slightly increased by 10% (multiplied by 1.1
) whenever the text hits a boundary, thus causing it to "bounce" back. We still keep the MathHelper.Clamp
as a safety measure to ensure the text remains within screen bounds.
What is the role of the GraphicsDeviceManager
and SpriteBatch
classes in the Game1
class? How do they differ?
In the Update()
method, why is it necessary to use MathHelper.Clamp()
for the text position?
Explain how the velocity
vector affects the movement of the text. What would happen if its x or y values were negative?
Challenge 1: Play with Color
Modify the Update()
method to gradually cycle the text color through the entire RGB spectrum, rather than just modifying the green component. You can do this by incrementing and looping each color component (R, G, B) individually using a switch
statement.
Challenge 2: Managing Game Time
Create a system that allows the text to move at a constant speed regardless of the frame rate. You'll need to use the GameTime
object passed to the Update()
method. The ElapsedGameTime
property can be helpful for this.
position += velocity;
: This adds to the velocity
to the position
for each frame. In essence, it's like saying . For example, if your initial position is (400, 300)
and your velocity is (2, 1)
, after one update, the new position becomes (402, 301)