Reducing the pixelated look of Variable Rate Shading on particle effects

Sammanfattning: As video games get more and more demanding and screen resolutions continue to increase, new methods to render video games at high frame rates are needed. Variable Rate Shading is a technique currently available on Nvidia’s Turing architecture and Intel Gen11 hardware. Variable Rate Shading makes it possible to pick a shading rate during rendering and shade a group of pixels instead of individually, ultimately speeding up the rendering. A drawback of Variable Rate Shading is that the image quality often degrades by producing a pixelated look. This paper aims to reduce the pixelated look of particle effects that are rendered through Variable Rate Shading by implementing and evaluating four different post-processing filters. A qualitative evaluation in the form of a user study took place to evaluate the work subjectively. Structural Similarity Index was another qualitative method used to evaluate the image quality objectively. Also, a quantitative evaluation was performed to measure how the render times vary. All Variable Rate Shading solutions were compared against a traditional method used in the industry to render particles effectively. Findings showed that when using 2x2 shading rate, which generally reduces shaded pixels by 75%, two of the solutions presented in this paper have better image quality than the traditional method and close to, but not equally good time performance for both 1080p and 4K resolution. 4x4 shading rate has more specific use cases such as smoke that consists of similar color over the entire effect or if 4K resolution is used. Using 4K resolution makes 4x4 shading rate potentially useful as the render times were the fastest, with an acceptable aesthetic look, while for 1080p resolution, it was not recommended. In conclusion, as video games are vastly different, an artist might be best suited to decide which implementation is best and how essential the reduction in render times are. Variable Rate Shading can be used to reduce render times and keep an appealing visual look