Understanding Render Scale: Complete Guide to Resolution & Performance

Rendering resolution is one of the most important factors that affects the visual quality and performance of a game. Modern games often need to balance high-resolution graphics with the processing power available on the target hardware.

Render scale provides a simple way to control this balance. Instead of rendering the game at the full native display resolution, a game can render internally at a lower or higher resolution and then scale the result to the final display resolution.

For example, a game running at a native resolution of 1920 × 1080 with a render scale of 75% renders internally at 1440 × 810.

Render scale is a percentage that determines the internal resolution used when rendering a game scene.

A render scale of 100% means the game renders at the full native resolution. A value below 100% renders at a lower internal resolution, while a value above 100% renders at a higher internal resolution.

Render scale is applied independently to the width and height of the native resolution.

This means that reducing the render scale does not simply remove a percentage of pixels from the final image. Both dimensions are reduced, which means the total number of rendered pixels changes much more significantly.

For example, reducing render scale from 100% to 50% halves both the width and height of the internal resolution.

The resulting image can then be upscaled to the final display resolution using the game's rendering pipeline or an upscaling technique.

The render scale calculation is straightforward. Convert the percentage into a decimal and multiply it by the native width and height.

For example, consider a native resolution of 1920 × 1080 and a render scale of 75%.

1920 × 0.75 = 1440

1080 × 0.75 = 810

Therefore, the internal render resolution is 1440 × 810.

The relationship between render scale and resolution becomes easier to understand when looking at common display resolutions.

At 1920 × 1080, a 75% render scale produces an internal resolution of 1440 × 810. The final image can then be displayed at the native 1920 × 1080 resolution after upscaling.

The same percentage can be applied to other resolutions. For example, a 2560 × 1440 resolution at 75% render scale results in an internal resolution of 1920 × 1080.

One of the main reasons developers use render scaling is to reduce the number of pixels that the GPU needs to process.

Because both the width and height change, the pixel workload does not decrease at the same percentage as the render scale.

For example, reducing render scale to 75% produces approximately 56.25% of the native pixel count before rounding.

This can provide a meaningful reduction in GPU rendering workload, particularly in games that are limited by pixel processing. However, render scale is not a guarantee of a specific frame-rate improvement because games can be limited by CPU processing, geometry, shaders, memory bandwidth or other systems.

There is no universal render scale that works best for every game. Developers typically test several values to find an appropriate balance between visual quality and performance.

These values are useful starting points, but the appropriate setting should always be evaluated on the actual target hardware and display.

Render scaling is a common optimization concept in modern game engines. Developers can use internal resolution scaling to adjust rendering workload dynamically or through graphics settings.

In Unity, render resolution can be controlled through the rendering pipeline and platform-specific graphics settings. The exact implementation depends on whether the project uses the Built-in Render Pipeline, URP or HDRP.

In Unreal Engine, resolution scaling is commonly used as part of performance and scalability settings. Developers can adjust rendering resolution independently from the final output resolution.

Lowering render scale reduces the internal resolution, which can make the final image appear softer or less detailed.

The visual impact depends on the render scale, the type of content being rendered and the upscaling technique used by the game.

Modern temporal and spatial upscaling techniques can reconstruct information from a lower-resolution render and produce a sharper final image than simple scaling alone.

Render scaling is relatively simple, but there are several common mistakes when using it as a performance optimization technique.

• Assuming that a 50% render scale means 50% of the original pixel workload.
• Expecting a guaranteed frame-rate increase from reducing render resolution.
• Using an unnecessarily low render scale without considering image quality.
• Testing only on development hardware instead of the target platform.
• Ignoring the game's upscaling or reconstruction method.
• Assuming the same render scale produces the same visual result across different rendering pipelines.

Render scale provides a straightforward way to control the relationship between internal rendering resolution, image quality and GPU workload.

Reducing render scale can significantly reduce the number of pixels that need to be processed. However, the resulting performance improvement depends on whether the game is actually limited by GPU rendering.

The best approach is to test several render scale values on the target hardware and choose the lowest setting that provides an acceptable balance between performance and visual quality.