Automated Asset Optimization for Mobile Games with Simplygon

When we talk about games that need automated asset optimization, traditional games often come to mind: huge AAA budgets, large MMOs, and complex assets. However, a growing segment of the gaming market is mobile games, which have different requirements and constraints. Yet, asset optimization remains essential.

Mobile games often rely on a free-to-play model where monetization comes from microtransactions or gacha mechanics. The content you pay for is usually additional art assets, such as special skins or characters. This means that asset creation cost is directly correlated to how profitable the video game is. In this blog, we will look at how to reduce the cost of art optimization, which can play a significant role.

Asset optimization for mobile games targeting different devices

Traditionally, when we talk about automated asset optimization, we think about generating LOD levels for a game where you view assets from different camera distances, like in an FPS game. This is not always the case for mobile games, which tend to have more static cameras. Automated asset optimization still serves a purpose in mobile game development.

Mobile games target a wide range of platforms, from cheap and old low-end Android phones to the latest iPhone. This means that performance requirements can vary significantly. Ideally, you want to perform different optimizations targeting different devices. This is where automated asset optimization comes in.

With Simplygon's triangle reducer, you can easily create different levels of detail for your assets, allowing you to optimize them for low-end, mid-range, and high-end devices. This means you can reduce the polygon count for lower-end devices while maintaining higher quality for more powerful devices. In our blog Low-poly character optimization, we shared a few tips on good reduction targets. Often, you can be more aggressive with your optimizations for mobile devices.

When developing for mobile platforms, it is important to always review the generated models in the proper context—on a mobile device. This ensures that performance is acceptable and that screen size and viewing distance influence how we see the models. We do not want to sit in our DCC tool and review the models.

Don't just optimize the model — optimize the character rig as well

For low-end devices, calculating skinning can be very taxing on both CPU and GPU. Having fewer skinning influences for each animated model improves performance. Optimizing rigs is especially important for mobile games where the characters are the main focus. In these kinds of games, you often have multiple versions of the character: a highly detailed one for when only the character is in focus, and a lower-resolution one for gameplay.

Optimizing the rig can be done with Simplygon's bone reducer. This tool can automatically reduce the number of bones and skinning influences in a character rig while preserving the overall shape and animation quality. By reducing the complexity of the rig, you can improve performance without sacrificing visual quality.

Optimize mobile game environments with hidden geometry removal and simpler shading

For mobile games, you want the environment to be as cheap as possible to render while retaining visual quality. This means using fewer objects, simpler geometry, and more efficient materials.

Our suggested tool of choice here is Simplygon's Object aggregation, which combines multiple objects into a single model. This simplifies the scene by reducing the number of draw calls and mesh transformations. This is especially useful for mobile games where performance is critical.

Aggregation can also perform geometry culling, which means it can automatically remove triangles that are not visible to the player. This can either be done by sampling cameras or volumetrically. Often a simple camera hemisphere is sufficient, but more complex camera setups can be used for better accuracy. For more information on this topic please read our blog Visibility culling and weighting with sphere and hemisphere.

The benefit of removing internal geometry is that overdraw is reduced. This also benefits lighting calculations depending on the technique used. In a baked lighting scenario, removing hidden geometry reduces the cost of lightmaps, saving texture memory. If the environment casts real-time shadows, then removing hidden geometry will reduce shadow calculations.

Consider merging as many materials together as possible using Simplygon's Material merging. This will significantly reduce draw calls and is a great way to gain control over texture usage in a scene. During material merging, depending on the desired quality level, you can switch to using simpler shading. For non-important distant objects, you can go as far as only using vertex colors.

Where to start

We suggest starting with what gives you the most performance gain, so benchmark the game on different mobile platforms and figure out what the bottlenecks are. Once those are identified, the next step is picking which tools from the above are suitable to address those issues.

With Simplygon's scripting API, it is easy to batch process optimizations across multiple assets. This allows you to quickly validate if addressing the bottleneck solves the performance issues.