Should the coordinates, and rotation angles of all the sprites be stored in variables?

Question

I've learned that magic numbers are bad in code. However, should the coordinates, and rotation angles of all the sprites be stored in variables? Is the convention in game development to leave those hard-coded values as arguments to set the coordinates or the angles of the transformable?

// Create a texture to hold a graphic on the GPU
Texture textureBackground;
// Load a graphic into the texture
textureBackground.loadFromFile("graphics/background.png");
// Create a sprite
Sprite spriteBackground;
// Attach the texture to the sprite
spriteBackground.setTexture(textureBackground);
// Set the spriteBackground to cover the screen
spriteBackground.setPosition(0, 0);
// Create a tree sprite
Texture textureTree;
textureTree.loadFromFile("graphics/tree.png");
Sprite spriteTree;
spriteTree.setTexture(textureTree);
spriteTree.setPosition(810, 0);
// Prepare the bee
Texture textureBee;
textureBee.loadFromFile("graphics/bee.png");
Sprite spriteBee;
spriteBee.setTexture(textureBee);
spriteBee.setPosition(0, 800);

Answer 1

For small games, it's okay to define these defaults locally in code directly. For anything more complex, it becomes rather unmanageable to keep it all in code.

That's when the data is moved into dedicated external files. This can be a simple JSON file that holds all the different sprites and their initial position. You'd then load this information at the beginning of a map/level/game and create the different shapes/textures/sprites/sounds.

As a side note, only really do this when your game gets bigger, because it introduces quite a bit more complexity, as your code has to be written more generically and can also consume quite a bit more effort to get the loading working smoothly. If you do achieve it though, it offers a lot of flexibility. You can modify the whole level or character with a simple edit of the config file and restarting the game or even implement some hot-reloading.

Answer 2

Storing values in variables is not the same thing as using magic numbers. The magic number anti-pattern is a direct usage of a number in the code.

For instance, compare the following code snippet:

currentHealth += 5;
if(currentHealth > 10) {
   currentHealth = 10;
}

Why are we increasing currentHealth by 5?
Why are we limiting currentHealth to a maximum of 10?
The values 5 & 10 are magic numbers - values being used directly in the code, and in this case, without a clear explanation as to why those particular values are being used.

That code should be refactored into something like this:

currentHealth += healthPotion.amount;
if(currentHealth > maxHealth) {
   currentHealth = maxHealth;
}

The second block of code is easier to read & maintain.

• It explicitly tells us that the current health is being changed because of a potion.
• It explicitly tells us that the potion shouldn't raise the current health past the maximum.
• We can presumably change the value for maximum health in one location, minimize the potential for errors.

Based on the description given, it does not sound like you have a magic number problem. If you need to track a sprites coordinates and rotation angle, member variables are a very sensible way to do so.

For more information & examples regarding magic numbers, you might want to read this Stack Overflow post.

Answer 3

Please keep in mind that you're reading a book explaining a way to make a game, in SFML. You will likely end up having a working game, but not one that is ready to ship.

To make it simpler for you to "get something working", they hard-coded the values instead of having you write a whole system to load a level from files.

This is fine, though. This kind of book is often the first step in getting you going. Once you're done with it, you'll then need to expand and "fix all the problems you see with it": adapt it for multiple screen sizes, make levels that are dynamically loaded at run-time, add a second playable character, etc.

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Is the convention in game development to leave those hard-coded values as arguments to set the coordinates or the angles of the transformable?

No, there is no convention.

Also, I suppose how much hard-coding there is will depend on the nature of the object.

I'm pretty certain some folks created HUDs completely by hard-coding values (coinCountLebel.position(screenSize.x() - 150, 0)) with the real desire to come back later and fix it before release, but yeah, they had to ship.

However, if you are to make a level by hard-coding your values, you'll realize that you're spending a lot of time in compiling your game just because you moved an object a few pixels.