Optimizing Your Art Assets

Art is a famously subjective discipline, dominated by personal opinion and preference. It can be challenging to say whether, and why, one piece of art is better than another. Oftentimes, our opinions won't be able to find a complete consensus. The technical aspects behind art assets that support a game's artistry can also be very subjective. Multiple workarounds can be implemented to improve performance, but these tend to result in a loss of quality for the sake of speed. If we're trying to reach peak performance, then we must consult with our team members whenever we decide to make any changes to our art assets, as it is primarily a balancing act, which can be an art form in itself.

Whether we're trying to minimize our runtime memory footprint, keep the smallest possible executable size, maximize loading speed, or maintain consistency...

Audio

As a framework, Unity can be used to build anything from small applications that require only a handful of sound effects and a single background track to huge role-playing games that need millions of lines of spoken dialog, music tracks, and ambient sound effects. Regardless of the actual scope of the application, audio files are often a significant contributor to the application size after it is built (sometimes called its disk footprint). Moreover, many developers are surprised to find that runtime audio processing can turn into a significant source of CPU and memory consumption.

Audio is often neglected on both sides of the gaming industry: developers tend not to commit many resources to it until the last minute and users rarely pay attention to it. Nobody notices when audio is handled well, but we all know what lousy audio sounds like—it's instantly recognizable...

Texture files

The terms texture and sprite often get confused in game development, so it's worth making the distinction: a texture is simply an image file, a big list of color data telling the interpreting program what color each pixel of the image should be, whereas a sprite can be seen as the 2D equivalent of a mesh—it defines how and where the image will appear in the game scene. Usually, a sprite is just a single quad (a pair of triangles combined to make a rectangular mesh) that renders flat against the current camera.

There are also things called sprite sheets, which are large collections of individual images contained within a larger texture file, commonly used to contain the animations of a 2D character. These files can be split apart by tools, such as Unity's Sprite Atlas tool, to form individual textures for the character's animated frames.

Of course...

Mesh and animation files

The mesh and animation file types are essentially large arrays of vertex and skinned bone data, and there are a variety of techniques we can apply to minimize file size while keeping similar, if not identical, appearances. There are also ways to lower the cost of rendering large groups of these objects through batching techniques. Let's take a look at a series of performance-enhancing techniques that we can apply to such files.

Reducing the polygon count

Reducing the polygon count is the most obvious way to gain performance and should always be considered. In fact, since we cannot batch objects using skinned mesh renderers, it's one of the good ways of reducing CPU and GPU runtime overhead...

Asset bundles and resources

We touched upon the topic of resources and serialization in Chapter 2, Scripting Strategies, and it should be fairly clear that the resource system can be a great benefit during prototyping, as well as during the early stages of our project, and can be used relatively effectively in games of limited scope.

However, professional Unity projects should instead favor the asset bundle system. There are a number of reasons for this. Firstly, the resource system is not very scalable when it comes to builds. All resources are merged together into a single massive serialized file binary data blob with an index list of where various assets can be found within it. This can be hard to manage, and take a long time to build as we add more data to the list.

Secondly, the resource system's ability to acquire data from the serialized file scales in an Nlog(N)...

Summary

There are many different opportunities that we can explore to achieve performance gains for our application just by tinkering with our imported assets. Alternatively, from another perspective, there are plenty of ways to ruin our application's performance through asset mismanagement. Almost every single import configuration opportunity is a trade-off between one performance metric or workflow task and another. Typically, this means saving the disk footprint via compression at the expense of CPU at runtime to decompress the data, or faster access while reducing the quality level of the final presentation. So we must remain vigilant and only pick the right techniques for the right assets for the right reasons.

This concludes our exploration of improving performance through art asset manipulation. In the next chapter, we will be investigating how to improve our usage...