A couple weeks ago I started writing a game and
i-can-management is the directory I made for the project so that’ll be the codename for now. I’m going to write these updates to journal the process of making this game. As I’m going through this process alone, you’ll see all aspects of the game development process as I go through them. That means some weeks may be art heavy, while others game rules, or maybe engine refactoring. I also want to give a glance how I’m feeling about the project and rules I make for myself.
Speaking of rules, those are going to be a central theme on how I actually keep this project moving forward.
- Optimize only when necessary. This seems obvious, but folks define necessary differently. 60 frames per second with 750×750 tiles on the screen is my current benchmark for whether I need to optimize. I’ll be adding numbers for load times and other aspects once they grow beyond a size that feels comfortable.
- Abstractions are expensive, use them sparingly.This is something I learned from a Jonathan Blow talk I mention in my previous post. Abstractions can increase or remove flexibility. On one hand reusing components may allow more rapid iteration. On the other hand it may take considerable effort to make systems communicate that weren’t designed to pass messages.I’m making it clear in each effort whether I’m in exploration mode so I work mostly with just 1 function, or if I’m in architect mode where I’m trying to make the next feature a little easier to implement. This may mean 1000 line functions and lots of global like use for a while until I understand how the data will be used. Or it may mean abstracting a concept like the camera to a struct because the data is always used together.
- Try the easier to implement answer before trying the better answer.I have two goals with this. First, it means I get to start trying stuff faster so I know if I want to pursue it or if I’m kinda off on the idea. Maybe this first implementation will show some other subsystem needs features first so I decide to delay the more correct answer. So in short quicker to test and expose unexpected requirements.The other goal is to explore building games in a more holistic way. Knowing a quick and dirty way to implement something may help when trying to get an idea thrown together really quick. Then knowing how to evolve that code into a better long term solution means next games or ideas that cross pollinate are faster to compose because the underlying concepts are better known.
The last couple weeks have been an exploration of OpenGL via
glium the library I’m using to access OpenGL from Rust as well as abstract away the window creation. I’d only ever ran the example before this dive into building a game. From what I remember of doing this in C++ the abstraction it provides for the window creation and interaction, using the
glutin library is pretty great. I was able to create a window of whatever size, hook up keyboard and mouse events, and render to the screen pretty fast after going through the tutorial in the glium book.
This brings me to one of the first frustrating points in this project. So many things are focused on 3d these days that finding resources for 2d rendering is harder. If you find them, they are for old versions of OpenGL or use libraries to handle much of the tile rendering. I was hoping to find an article like “I built a 2d tile engine that is pretty fast and these are the techniques I used!” but no such luck. OpenGL guides go immediately into 3d space after getting past basic polygons. But it just means I get to explore more which is probably a good thing.
I already had a deterministic map generator built to use as the source of the tiles on the screen. So, I copy and pasted some of the matrices from the
glium book and then tweak the numbers I was using for my tiles until they show up on the screen and looked ok. From here I was pretty stoked. I mean if I have 25×40 tiles on the screen what more could someone ask for. I didn’t know how to make the triangle strips work well for the tiles to be drawn all at once, so I drew each tile to the screen separately, calculating everything on every frame.
I started to add numbers here and there to see how to adjust the camera in different directions. I didn’t understand the math I was working with yet so I was mostly treating it like a black box and I would add or multiply numbers and recompile to see if it did anything. I quickly realized I needed it to be more dynamic so I added detection for the mouse scrolling. Since I’m on my macbook most of the time I’m doing development I can scroll vertically as well as horizontally, making a natural panning feeling.
I noticed that my rendering had a few quirks, and I didn’t understand any of the math that was being used, so I went seeking more sources of information on how these transforms work. At first I was directed to the OpenGL transformations page which set me on the right path, including a primer on the linear algebra I needed. Unfortunately, it quickly turned toward 3d graphics and I didn’t quite understand how to apply it to my use case. In looking for more resources I found Solarium Programmers’ OpenGL 101 page which took some more time with orthographic projects, what I wanted for my 2d game.
Over a few sessions I rewrote all the math to use a coordinate system I understood. This was greatly satisfying, but if I hadn’t started with ignoring the math, I wouldn’t have had a testbed to see if I actually understood the math. A good lesson to remember, if you can ignore a detail for a bit and keep going, prioritize getting something working, then transforming it into something you understand more thoroughly.
I have more I learned in the last week, but this post is getting quite long. I hope to write a post this week about changing from drawing individual tiles to using a single triangle strip for the whole map.
In the coming week my goal is to have mouse clicks interacting with the map working. This involves figuring out what tile the mouse has clicked which I’ve learned isn’t trivial. In parallel I’ll be developing the first set of tiles using Pyxel Edit and hopefully integrating them into the game. Then my map will become richer than just some flat colored tiles.
Here is a screenshot of the game so far for posterity’s sake. It is showing 750×750 tiles with deterministic weighted distribution between grass, water, and dirt::