Optimizing 2D Games To Support A Wide Range Of Devices And Displays
The core problem: Supporting many different screen sizes and resolutions
A key challenge in 2D game development is supporting a wide variety of display resolutions and aspect ratios. With players accessing games on monitors, TVs, phones, tablets, and more, developers must ensure their games can scale and adapt to different resolutions and sizes.
Screens come in many different resolutions – the number of pixels horizontally and vertically. Common resolutions include 1920×1080 (1080p), 2560×1440 (1440p), 3840×2160 (4K), and more. Screens also have different aspect ratios, which is the proportional relationship between width and height.
If developers lock their games to one specific resolution, issues can arise. Lower resolution displays will show smaller UI and sprites, reducing playability. Higher resolutions may show UI elements too large, with wasted space and cropped image content. Supporting many resolutions is key.
Common screen resolutions for 2D games
Lower resolutions like 800×600
While higher resolutions like 1080p and 4K grow in popularity, lower resolutions still see significant use. An 800×600 resolution was once very common for monitors and laptops. Today it remains popular for netbooks, older hardware, and handheld devices.
An 800×600 resolution only offers 0.48 megapixels of display area. With such little screen real estate, fitting detailed interfaces and graphics can pose challenges. Developers must carefully consider information density and balance playability on these lower resolution displays.
Higher resolutions like 1080p and 4K
Higher definitions like 1080p (1920×1080) and 4K (3840×2160) are quickly becoming more popular. 1080p monitors and TVs are common among modern gaming PCs and consoles. 4K displays are rapidly dropping in price as well.
The increased resolutions offer more real estate but also bring challenges. Higher pixel counts require more processing power to render. More screen space allows tighter and busier interfaces, but these can overwhelm players. Supporting ultra HD resolutions requires both technical and design considerations.
Sprite and texture considerations
Using sprite sheets
Sprites are 2D bitmap images used to represent game characters, items, backgrounds, and other graphical elements. Sprite sheets combine multiple sprites into a single texture asset. Using sprite sheets brings performance optimizations but also some design constraints.
With sprite sheets, developers avoid the overhead of issuing multiple draw calls per frame. Combining assets also better enables batching to the GPU. However level and character designs must work within the constraints of the sprite sheet size and layout.
Choosing intelligent sprite sheet dimensions is vital. Very large sheets can limit device compatibility, while small sheets impose design restrictions. Adaptive sprite sheets that scale assets to resolution can help strike a balance.
Setting maximum texture sizes
In addition to sprite sheets, games use texture assets for backgrounds, UI elements, visual effects, and more. Setting appropriate maximum sizes for these textures improves performance and compatibility.
Larger texture dimensions allow more detailed assets, but require more graphics memory.Maximum sizes between 2048×2048 and 4096×4096 balance quality and compatibility for most 2D games. Supporting runtime texture size scaling can optimize this on a per-device basis.
Textures beyond 8192×8192 often exceed integrated GPU capabilities. Testing assets on target mobile, console, and laptop hardware is important to determine ideal texture size thresholds.
Handling different aspect ratios
Letterboxing content
Displays come in different aspect ratios, which pose challenges when designing 2D game interfaces, backgrounds, and camera behaviors. A common approach is letterboxing – filling unused areas with bars.
For example, a 16:9 widescreen display playing a 4:3 ratio game may show vertical bars on the left and right. While this wastes some display space, it allows the core game content to retain correct proportions without distortion.
Adaptive UI elements can avoid the need for letterboxing in some cases. Careful background asset design is needed so critical game elements are framed correctly on both wider and taller aspect ratios.
Adjusting UI elements
Carefully constructing in-game interfaces enables supporting varying display ratios without letterboxing or cropping. Interfaces built using relative element positioning and scaling can gracefully adapt.
Positioning elements based on percentages rather than absolute pixels allows flexibility. Fonts and UI assets can scale dynamically based on changing resolution and aspect ratios at runtime.
Testing interface designs on multiple aspect ratios early in development can inform intelligent adaptive layouts. Reflowing long text blocks, strategically positioning scene elements, and scaling major UI components are key considerations.
Scaling game graphics
Pixel perfect vs smooth scaling
Game interfaces and sprites can scale in two primary ways – pixel perfect, or smooth/blurry. Pixel perfect scaling gracefully handles resolutions multiples of the source assets. However non-multiples will show blurriness without special handling.
Pixel perfect scaling locks assets to integer multiples for a crisp retro pixel art style. Smooth scaling uses filtered resampling algorithms, ideal for 3D games where precision isn’t as vital. Hybrid approaches are common as well.
Pixel perfect rendering suits 2D games when sharpness is more important than anti-aliasing for the visual style. Smooth scaling prioritizes softness over accuracy. Weighing these trade-offs helps inform the optimal display scaling approach.
Integer scaling techniques
New integer scaling algorithms provide pixel perfect sharpness without requiring exact resolution multiples. These examine source pixel ratios and resample screens to best match native sizes.
Integer scaling avoids subpixel color blending that causes blurriness at non-native resolutions. Machine learning super sampling further enhances results. When implemented well, crispness can be maintained regardless of display size.
Powerful GPU pixel shaders make integer scaling possible in real-time game engines. Adaptive asset loading and intelligent pre-rendering can further optimize when to use this advanced scaling technique.
Testing on multiple devices
Physical devices
Emulators provide great convenience for testing 2D games on various target platforms. However real-world testing on physical devices still plays a vital validation role for resolution support and performance.
Factors like refresh rates, display calibration, thermal throttling, and manufacturing variance can influence how games appear and handle on actual devices. Testing on real smart phones, tablets, laptops, and monitors is invaluable.
Developers should assemble a test battery of devices spanning generations, OS versions, and capability ranges. Testing early and often on real world hardware can expose compatibility issues and areas for optimization.
Emulators
Game system emulators emulate target platform hardware, enabling convenient testing across many devices virtually. Android emulators like BlueStacks along with console emulators provide key testing capabilities.
Emulators empower iteratively testing gameplay on systems a developer may not physically own. Quickly validating changes across resolutions and alternate device types can accelerate development. Automated testing harnesses multiply the testing possibilities.
However, emulators carry some variance from real system operation. Periodic validation on physical devices ensures accurate simulation and provides supplemental confirmation of performance.
Optimizing performance
Texture compression
As texture resolutions and counts scale up, graphics memory bandwidth strains can arise, especially on mobile chips. Texture compression formats help improve performance by reducing asset file sizes.
Formats like ETC2 on Android and PVRTC on iOS squeeze textures down while retaining reasonable fidelity. Level designers can author assets tailored to compression constraints for further gains.
Crunching textures offline during asset processing stages quickens run-time performance. Compression parameters can scale dynamically based on detected device capabilities for an optimal blend of quality and speed.
Fewer/smaller draw calls
Draw calls issue commands to render sprites, textures and meshes. Minimizing draw calls and keeping remaining draws batched into larger groups can significantly improve rendering efficiency.
Sprite sheets, asset atlasing, and intelligent scene culling are key techniques. Analyzing per-frame draw call numbers helps quantify batching improvements during optimization. Targeting under 100 peak draw calls offers smooth gameplay.
Reducing individual draw sizes also carries performance benefits. Larger batch counts allow leveraging faster GPU pathways. Designing 2D scenes and effects to enable efficient batching takes consideration from the beginning.
Batching
Batching combines multiple draw calls together into single larger constructs for more efficient GPU processing. This amortizes fixed function overhead across many assets.
Carefully sorting transparent and blended objects minimizes costly state changes within batches. Custom renderers can further optimize batch counts, sizes, and contents per scene and target platform.
Multi-threaded rendering divides batches effectively across CPU cores as well. Analyzing performance analyzers helps guide batching optimizations for smoother gameplay on all systems.
Setting graphical options
Resolution scaling
When supporting many resolutions, offering graphical options for players to scale rendering down from native resolutions can improve performance on lower powered devices.
50% downsampling dims each axis by half while maintaining crisp image quality. Dynamic scaling factors can adjust from 20% to 100% based on real-time performance data to sustain framerates.
Resolution scale sliders provide an intuitive control for players to balance graphical fidelity and smoothness. Intelligent presets tailored per device also simplify getting optimal settings.
Enabling/disabling effects
Beyond resolution, allowing players to selectively enable or disable certain graphical features helps optimize for their systems’ capabilities.
Post-process effects like bloom, depth of field, motion blur and anti-aliasing carry some of the highest GPU costs. Allowing these to be disabled prevents the game from overtaxing lower end hardware.
Particle counts, shadow resolutions, texture filtering modes, and more graphical features provide further tuning dimensions. Exposing the most costly settings enhances playability across devices.
