Posts tagged “programming”

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Writing a test DSL in Kotlin

As I previously wrote, I recently fell in love with the Kotlin language. It’s been over four months since that post, and my enthusiasm has not diminished. In this post, I’ll show how I combined some of Kotlin’s best features to write some extremely readable unit tests. The thing we’ll... Continue reading

Texture compression on mobile demystified

If you’re developing a game for mobile devices, chances are you have run into the words “texture compression”. Texture compression helps to keep video memory usage down, reduce download sizes and loading times, and may even reduce power consumption. In this article, I take a comprehensive look at what the... Continue reading

10 cool things about Kotlin

Kotlin is a programming language developed by JetBrains (the makers of IntelliJ IDEA), which compiles down to Java bytecode. I got over my initial aversion for the ugly name, and decided to give it a try. Now I never want to go back to Java. Here’s why. 1. Full Java... Continue reading

10 reasons to love C++

In the past few years, I’ve done most of my game development in Java. It didn’t use to be that way. Before Android and libGDX came along, when C++11 was still C++0x, I used C++ almost exclusively. And recently, because of some performance-critical bits in Mystery Game No. 1, I... Continue reading

SRY: Sometimes Repeat Yourself

Any programmer worth their salt will have heard of the DRY principle: Don’t Repeat Yourself. The idea is that repetition is bad: it makes for more code to read through, and it makes code harder and more error-prone to maintain because you have to make the same change in multiple... Continue reading

Localizing libGDX games via a spreadsheet

LibGDX has decent localization support via a bundle of .properties files, for example: == == app_name=Confirmation App confirmation=Are you sure? == == confirmation=I'm terribly sorry to bother you, but would you please be so kind to confirm your certainty on this matter? == == confirmation=Weet u het... Continue reading

Bigcanvas: Concurrency

Core to the idea of Bigcanvas is that it’s a shared space, where everyone can draw at the same time. Much as it would on a real canvas, this means people can interfere with each other. Properly handling this and making sure that everybody’s brush strokes made it onto the... Continue reading

Bigcanvas: Technology

How does one store the contents of an infinite canvas into a computer’s finite memory? One cheats. In this case, by taking advantage of the fact that the canvas may be infinite, but people’s drawings are quite finite. We simply don’t store the empty regions. To that end, the canvas... Continue reading


Ladies and gentlemen, Frozen Fractal presents… Bigcanvas! It’s an infinite online canvas that anyone can draw on. The ‘why’ is described within the app itself, so have a look! This blogpost focuses on the technical aspects, i.e. the ‘how’. Just for fun and challenge, efficiency was one of the main... Continue reading

Goodbye JavaScript

The JavaScript server code for Turtle Paint is becoming increasingly difficult to manage. People had warned me beforehand, but there’s no teacher like first-hand experience. The problems in a nutshell: Immaturity. Often, there are five different Node.js libraries that do approximately the same thing, but all of them are buggy... Continue reading

Bits and pieces

Game development can be a pain sometimes. Remember my writings on threading last week? This week has been more of the same kind of stuff: engine improvements, code cleanups, bugfixes, and only some small new features that are actually visible. Did I say visible? I meant “audible”. The biggest change... Continue reading


More work on performance this week. Things were getting a bit too slow for my tastes, meaning that they would likely be unplayable on medium-end phones. This work involved quite a bit of refactoring (which is jargon for “creating new problems to replace your old ones”), so I now have... Continue reading

Game architecture

Although games vary wildly in appearance and mechanics, the structure of the underlying classes and objects is often similar. There is a “world” object, which contains everything else; there are multiple “entities” representing stuff in the world, there’s a “renderer” which tells each object to draw itself, etcetera. My game... Continue reading

Performance measurements

After a week partly filled with lots of food and other Christmas celebrations, I’m back on track. I’ve done some polishing to make the game more game-like. There’s now a neat countdown at the start of the game. You can start racing before the countdown ends, but there’s a little... Continue reading

Texture compiler

After the model compiler comes the texture compiler. Decompressing a PNG file on Android is possible, but the loading code is simpler if the texture is already available in a format that we can feed directly to OpenGL. So I devised the GLT (GL Texture) format, and wrote a program... Continue reading

Model compiler

Having a level editor is a good start, but it’s not all. We need some kind of workflow to create models and textures and eventually get these to show up in the game. I started with the models. Since I know my way around Blender and it’s free, I decided... Continue reading

Two problems become none

No truism is always true, not even this one. I recently clashed with two common conceptions in software engineering: “All problems in computer science can be solved by another level of indirection.” – David Wheeler “Some people, when confronted with a problem, think ‘I know, I’ll use regular expressions.’ Now... Continue reading

Sandbox editor

To be able to test different configurations, I had a rudimentary text-based file format to describe levels in. It was fairly simple and easy to edit, but still, hand-typing coordinates is not my idea of fun. It was time to build a graphical editor. I plan to release the editor... Continue reading

Stam solver working

This week I worked hard on getting the fluid solver in the style of Jos Stam working. The basics were easy enough, but Stam makes some simplifying assumptions, so the continuation was not quite trivial. But combined with what I learned in my earlier work on the free-surface simulator, I... Continue reading

Fluid solver on the GPU

Work on this project has been standing still for some time while I was working on another project. But this week I picked up work where I left off: making the fluid simulation even faster. Since the SOR solver I was using lends itself well to parallelization, and video cards... Continue reading

Optimization story

The fluid simulation was beginning to approach results of decent quality. However, it was still far too slow. Most of the screenshots I’ve shown so far were done on a 64x64 grid, which barely ran in real-time even on my fast Intel i7 machine. For a full-screen game, I’d need... Continue reading

The joy of graphical debugging

I’m a very visual type of guy. A picture really does say more than a thousand words. It should come as no surprise that my way of coding and debugging reflects this. How does one debug a fluid solver? It is possible to step through the code, but that does... Continue reading

Fluid still failing

It’s been a busy week with little to show for it. As I wrote last time, I more or less gave up on the SPH particle-based method, and opted to fix my grid method instead. That turned out to be harder than I expected. As a first attempt, I tried... Continue reading


To find the source of the instabilities, I pulled my code apart into more independent steps, that could individually be turned on or off. This did result in a speed hit, but allowed me to quickly trace the source of the problems to the advection routine. This is the part... Continue reading

Lid driven cavity

Since no existing code fit my requirements, I started working on my own fluid simulator a few weeks ago. The idea was to try both a grid-based and a particle-based method, and see which worked better for my situation. I started with the grid-based version. My code was not based... Continue reading