Jetboard Joust Devlog #76 – It’s All Relative

Sometimes with code you just have to pick it all apart and start again – and that’s exactly what I’ve been doing for the last day and a half.

Like its main inspiration ‘Defender’, Jetboard Joust has a game world that ‘wraps’, ie once you leave one side of the world you enter at the other – a bit like Pac Man in his maze with the difference that, as the camera is permanently fixed on the player, the effect isn’t so immediately obvious.

To date I’ve been using the obvious approach to this, an approach that I’ve always used when coding this type of game. When the player leaves one side of the world the horizontal size of the world is added or subtracted to/from the player’s location and they appear at the other side. It’s straightforward in principle, seems to make logical ‘sense’, and for the most part works.

But there’s always been these little niggles when gameplay occurs around the area where the world ‘wraps’ and I’ve found myself writing lines and lines of code to circumvent issues to do with drawing (particularly some particle effects), collision detection, and AI. Most of these problems have been solvable without too much hassle but I kept thinking ‘there must be a better way…’.

Then, for no particular reason, a light bulb went off and I had the idea of dealing with wrapping relative to the player rather than to the world itself. In this scenario the player never ‘wraps’, their location just keeps increasing or decreasing as they travel in one direction, but if anything else in the game world finds itself more than half a world width away from the player the width of the world is added/subtracted to/from its location to position it on the other side of the player.

Whilst this method doesn’t really make logical ‘sense’ (static objects like buildings are jumping all over the place in the game world) it actually works much, much better in practice. The real beauty of this system is that if any glitches do occur due to the sudden jump in location caused by wrapping, they happen way off screen so the player is never aware of them – and as fast-moving objects such as projectiles, particles etc only really appear close to the player wrapping code can be completely omitted for these items.

Implementing this was a major change for the game engine and I proceeded very gingerly at first, making sure I preserved the ‘old’ method of doing things in case I needed to switch back, but it soon became obvious this was the right way to go. Various minor bugs have been completely eradicated and I was finding myself able to comment out large swathes of code. Debugging at the ‘wrap point’ is now pretty much a non-issue! I’ve eradicated a fairly major development headache in preparation for working on the enemies.

Dev Time: 1.5 days
Total Dev Time: approx 153.5 days

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A Trip Round The World As Seen On The Game Scanner

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One Of The Vast Swathes Of Crap Code I Was Able To Dispense With
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