Monday, May 21, 2012

Fixing Long Load Times in Shatter Crash

Development on Shatter Crash is moving along pretty well, we are currently working on polishing, UI and bug fixing.  One of the things I decided to tackle today was the long load times we were seeing when traveling from our game play scene back to the main menu scene.  This was especially bad on the iPad's, where we could see load times between 10 and 15 seconds.

The first thing I did was use Unity's cool profiler tool to get a sense of where time was being spent by running the game on my computer. However this ended up failing horribly because the editor continually stalled or crashed while I did deep profiling, probably because the call trees were incredibly deep.  Doing regular, non-deep profiling, didn't flag anything that jumped out as problematic, so I began to suspect the issue had to do with asset loading. As a note, as far as I know Unity's profiler doesn't give much details about asset loading/unloading, so this was simply a theory. (As a note, I didn't have wifi access at the time, so was unable to directly profile the game running on the device.)

I began to suspect the extended load times had to do with our GUI solution forcing Unity to pull in a lot of textures and create a number of object hierarchies.  I tested this by creating an iPad build with most of the UI ripped out to see how much faster the main menu loaded.  To my surprise, it only dropped the load time from ~15 seconds to ~14 seconds...looks like the GUI isn't to blame. I eventually resorted to brute force debugging by removing objects from the scene and pushing a new build to the device to see if things got better.  This certainly wasn't an ideal debug flow, but it did work.

I eventually found the cause of the load time spikes was related to how we referenced the puzzle data for Shatter Crash's game levels.  Our puzzle data is stored in ScriptableObjects for convenience, and each 'level' contains lists with hundreds, or thousands, of entries which define each piece on a puzzle board. For simplicity, I had created a script and prefab which directly referenced each of these puzzle ScriptableObjects (about 30), and this prefab was referenced in the main menu.  Removing the reference to this puzzle container prefab dropped our load times from ~15 to ~3 seconds...sweet problem found!  It seems Unity was taking a long time to load the main menu because it was loading and parsing all the list data in each of the puzzle data files.

Now that I knew the cause of the problem, the fix was fairly straightforward, although a bit tedious.  I changed the puzzle loading system to use Resources.Load to dynamically load the puzzle data we needed on-demand.  I generally shy away from using the Resources.Load() much because it's a real pain in the butt to keep asset paths up-to-date, and when I do I generally write unit tests to validate the existing paths are good.  While I was copy pasting strings, I came up with an idea for a new tool to automatically create Resource paths, hopefully I'll have a chance to create it in the near future

*UPDATE* - The game described here was ultimately released as 'Shatter Crash'.  I edited several places where I referenced it by its old name 'Access Point' to refer to the new name

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