Category Archives: programming

SQL headache

April 28, 2015 | Filed under: programming

Gah, I spent all morning wracking my brains to fix a rendering order batching bug (fixed! yay!), and now I suddenly have a second daily headache with some SQL. If you use SQL a lot you can probably tell me how trivial this is…

Imagine a table of scores

DaveĀ  PlanetA 4,200

Mike PlanetB 2,200

Dave PlanetA 4,100

Chas Planet A, 7,200

And so on. What I am doing right now is a SELECT to get the top 20 rows from this table where the planet is (for example ) PlanetA. What I *want*n to do is to get the top 20 rows, but only the TOP entry for each player. So you only appear once in each high score list.

I can’t get my head around how to do that. I want something like SELECT * FROM scores WHERE scores.planet == ‘zog’ AND scores.score IS HIGHEST FOR score.player ORDER BY score

But of course I’ve made that syntax up and its imaginary. Albeit cool.

Tell me there is an easy way to do this thang?

And ooh guest what! Democracy 3 is the #1 strategy game on the ipad right now, due to a rather insane price drop I’m experimenting with…

Yikes,. so we had a lot of MUST FIX NOW issues in the first four days of releasing Gratuitous Space Battles 2. I think in retrospect I had bitten off a bit more than in possible for a single coder / designer to do.

GSB2 involved a phenomenal amount of re-engineering to support the kind of graphical fidelity I wanted. I sometimes read comments like ‘its just a new engine’, as though I just went into a drop-down box in unity and selected ‘new engine’, then hit the ship-it button. Arrggghhh. This new engine took well over a year of mind-mangling stress to develop. I love it, but its still hard work.

Anyway… Lesson learned #1: Multithreading increases your bug count by at least tenfold. Especially on ‘other peoples hardware’.


Lesson learned #2: Don’t do a multi-platform release. Do a Windows release. Fix everything, THEN worry about mac & Linux. Or hire another 3 or four people. Or make a much, much simpler game.

The good news is that after tracking down some pretty obscure stuff, I’ve got version 1.26 out there, and early reports suggest it is MUCH better. MUCH more stable, and a lot of silly dumb-ass mistakes by me have been fixed. The only *big* bug left is some series of actions that leads to ship designs being (temporarily) deleted until you restart the app. I reckon thats easily fixable today. Which then means I can get on with what I wanted to be doing all along: tweaking values, improving GUI elements, supporting modders, and getting a feel for what features people would like improved or added. I know people want galactic conquest put in, but thats a HUGE project, and not one for the next few months. That didn’t ship with GSB1, and that was with good reason, I assure you. Every single weapon and module from every race & expansion pack of GSB1 is in GSB2. It also has more initial missions, but even then people complain it doesn’t have enough content. Argggghhh.

Anyway, at least I can smile now for the first time in a few days. If you are enjoying the game, please leave a positive steam review. Even better, tweet about it :D.

Supporting modded content

April 04, 2015 | Filed under: gsb2 | programming

Supporting mods is normally pretty easy, especially if you have your data left pretty open. The place it gets tricky for GSB2 is online challenges. People post their fleet to other players as a challenge, and this works great when the only content in your challenge is content you *know* the other player has on their hard drive, but the minute you allow modding it gets kinda complex.

It’s pretty late in GSB2’s development for me to realize (less than two weeks from release) that the way I was handling it was not actually working, so yesterday I had to go back to the drawing board, and I have high hopes it will be cracked by the end of the day, especially regarding the most likely form of modding, which is extra hulls, modules and ship components (visuals).

When people posted a challenge in GSB1, it was just a binary GSB file. I had a really rubbish system where the player had to tick boxes when issuing a challenge saying what extra DLC content might be included. In fairness, the game did actually check on launching a challenge and warn people if they needed extra content, but it really did kinda suck.

With GSB2 I’m improving this. I hacked the mod-content code last night so it told each piece of moddable content (module/component/hull) what mod is came with. The base game has been designated as just another mod, which makes this nice and easy. Then, when I post a challenge, the game can scan through every ships hull, module and component and make up a list of all the content packs required, which in 99% of cases will be just the base game. In then sticks that in the header file for the challenge.

Theoretically I can parse that file on the server and store it in a database, and thus show a player what content requires mods and what doesn’t. Also theoretically I can direct them to the download page for that mod. In an ideal world, I’d break mods apart automatically upon submission and handle the file delivery along with the challenge, so you would magically get any extra required content. The bandwidth requirements there might be a pain, and this is all fantasy work for after release.

But I am at least confident that I will release with a system that at least lets people put together mods, and use them within challenges without any confusion or random crashing. Worst case situation is a popup on a challenge saying “sorry, this requires the ‘l33t ship hulls mod’ and you don’t have it yet!”. That will just be phase one.

GSB2 had a superb modding scene, and I want to be supporting that in GSB2 from day one. I suspect the ship design steam workshop submission stuff will help get people interested in the mod scene better, and the integration of a mod control panel will also make mod management a lot easier.



So here is something you might enjoy, especially if you like gratuitous charts and stats porn, or are interested in graphics programming, or maybe you just want to tell me I’m doing it wrong. This is a video of me demonstrating nvidia nsight, and how I use it to spot things that are inefficient in my engine for Gratuitous Space Battles 2. I’ve already fixed the two inefficiencies I point out in the video, while I was waiting for it to upload :D Enjoy! (And please share!)

multithreading sound engine bug…

February 28, 2015 | Filed under: programming

I have a bug thats driving me nuts. I use some middleware as a sound engine. its the ONLY middleware I use, and its bugging me. theoretically its easy to use, but I have a situation that it seems incapable of coping with.

With this middleware, I can play a sound, and request a pointer to track it. I can use that pointer later to adjust volume, or stop the sound, or query if its finished. For various reasons, I need to keep my own list of what sounds are currently playing. Thus I have a list of ‘current playing sounds’.

The middleware gives me a callback which triggers when a sound ends. This is handy, as I can then loop through the current playing sounds and remove it, keeping that list up to date. The sound engine runs in its own thread, so that callback triggers in a different thread to the main game.

This is where it goes wrong (but only on fast speed). I decide from the main game, to stop a sound. I firstly check that the sound exists within the current playing sounds. It does, so I access the sound pointer and tell it to stop. But wait! in-between those two events, the sound has expired naturally (in another thread) and the pointer has become invalid. CRASH.

using critical sections just produces race conditions, because stopping the sound has to happen in the same thread as the callback, and there are likely several sounds generating callbacks in the same frame (on fast speed) as the one I’m trying to stop, and it reaches a deadlock. It’s a real pain.

One solution is to make all such sounds loop (and thus never expire naturally, and rely on me killing them, which should work ok) and I thus never hit this problem. Another is to just not stop them prematurely (looks weird). I have currently hacked it, but I suspect the 1.18 build still has this issue manifesting itself as a 4x speed lots of beam-lasers crash.

Another solution is to tell the sound engine to run single threaded but that seems horrendously hacky.

I may have to try the always-loop solution. One day I’ll write my own sound engine again.