Optimizing Unity Games for iOS

Triangle comparison of a Unity plane, a simple plane and zombies

Triangle Comparison: Unity plane (Left), simple plane (Right) and zombies

This post is about something a little different, I’ve spent a lot of time fussing with optimization during the course of Lunacy’s development and I thought I should share some of the more obscure things I’ve learnt, on the off chance I can save somebody else hassle in the future.

There’s already a lot of information on the web about the more common approaches to optimization, lowering frame rates, removing lag etc. Repeating all that information isn’t the purpose of this post, so to that end I’ll only provide links to the following webpages, which were a great help to me.

Optimising with Unity for iOS by Jamie McCarter

Unity Manual: Optimizing Graphics Performance

Optimizing with Unity iPhone, the first three things I’ll do… by Cratesmith Gameworks

The actual purpose of this post is to highlight a few of the less well-documented potential sources of lag/lower frame rates I’ve run into so far:

1. Unity Planes
Unity planes, (the ones from game object -> create other -> plane), are not your friend. Firstly they come with mesh colliders, you’ll want to change these to box colliders, as mesh colliders are more intensive. (And as far as I can tell, completely unnecessary for a plane.) Secondly, these planes consist of a great many triangles, so you could potentially stand to gain by replacing them with simple (two triangle) planes you’ve brought in from a 3d modeling program. Doing so will make you unable to effectively use vertex lighting on the planes or things like fog. However if you’re not using fog and using baked light mapping, which you’ll probably want to do as its less intensive, then the 2 triangle planes should serve you fine.

2. Too Many Active Objects
Now this may seem ridiculously obvious, but it wasn’t for me so for the sake of any likeminded folk reading this I’m including it.

My trail of thought was that I would be able to get away with large amounts of objects as long as they weren’t within the camera’s rendering range, weren’t referred to by any active scripts and were just simple objects. I tested this with basic cubes with box colliders in Lunacy, queried Unity Answers, but ultimately came to the conclusion that I was completely wrong.

As long as the objects are toggled to active, even if they’re very simple, are not having their polygons rendered and are not interacting with anything, they will still cause a significant drain on performance in large numbers.

We had always intended to have fairly large and expansive areas in Lunacy, to compensate for us not having the manpower to produce a large variety of them. But of course large areas require lots of objects and I ran into this issue. Ultimately to counter act this issue I scripted a system in which all the environmental objects in each area are activated and deactivated in tile-marked segments as the player moves around. The cost of this is the occasional brief loading pause mid level, but it’s a price we’re willing to pay.

3. Dynamic Text
This one comes down to using a custom font set to dynamic, as they are by default. (Set under “Character” in the font import settings.) Dynamic means that Unity generates a texture for each character in the font on-the-fly the very first time that character is displayed. I’ve found in certain circumstances this can cause tiny lag spikes the first time specific characters are displayed. A simple enough solution to this issue is changing “character” in the font import settings to ASCII default set. Though this will mean you’re stuck with only one font size per font file and can’t align the font to center or right.

A Final Note
I should stress these are simply things I’ve found to be the cause my own problems via my own experiments, so they won’t necessarily be the cause of any problems you might be having or even be worth worrying about in your game.

Furthermore, this is my first time working on an iOS game, I’m still learning, so if somebody out there does have reason to disagree with any of my conclusions or can shed light on why number 2 happens, do let me know!

I should also mention that we’re developing in the free version of Unity 4, so if you have Unity Pro I imagine point number 2 could be less of an issue, as you can use static batching.

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About Tom

I’m a games design graduate with one simple (and rather predicable) goal, to make fun games. My weapons of choice are Photoshop, Blender, C# and Unity, whilst my favored platforms are iOS and Windows Phone. My blog, None Studios, plays host to all my games published, planned or somewhere in between.

Posted on May 2, 2013, in Uncategorized and tagged , , , , , , , , , , , , , , , , . Bookmark the permalink. Leave a comment.

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