Abstract
When the rendering budget is limited by power or time, it is necessary to find the combination of rendering parameters, such as resolution and refresh rate, that could deliver the best quality. Variable-rate shading (VRS), introduced in the last generations of GPUs, enables fine control of the rendering quality, in which each 16×16 image tile can be rendered with a different ratio of shader executions. We take advantage of this capability and propose a new method for adaptive control of local shading and refresh rate. The method analyzes texture content, on-screen velocities, luminance, and effective resolution and suggests the refresh rate and a VRS state map that maximizes the quality of animated content under a limited budget. The method is based on the new content-adaptive metric of judder, aliasing, and blur, which is derived from the psychophysical models of contrast sensitivity. To calibrate and validate the metric, we gather data from literature and also collect new measurements of motion quality under variable shading rates, different velocities of motion, texture content, and display capabilities, such as refresh rate, persistence, and angular resolution. The proposed metric and adaptive shading method is implemented as a game engine plugin. Our experimental validation shows a substantial increase in preference of our method over rendering with a fixed resolution and refresh rate, and an existing motion-adaptive technique.
Highlights
Shading is one of the most computationally expensive parts of the rendering pipeline, yet the demand for shading computations is growing significantly with the increase of both the resolution and refresh rate of displays
Variable-rate shading (VRS) has been used to exploit the limits of the human visual system (HVS) by intelligently distributing the shading budget based on foveation [Tursun et al 2019], scene content and motion
Our model provides an opportunity to study the interplay between luminance and persistence (Figure 9) for rendering on the upcoming variable persistence-variable refresh rate displays [Hekstra et al 2008; Verbeure et al 2017]
Summary
Shading is one of the most computationally expensive parts of the rendering pipeline, yet the demand for shading computations is growing significantly with the increase of both the resolution and refresh rate of displays. With the growing popularity of mobile gaming, which needs to operate under a limited power budget, and GPU sharing cloud gaming [Yadav and Annappa 2017], rendering often needs to operate at a fraction of the maximum GPU capacity To address this challenge, all popular GPU manufactures have introduced a more flexible shading mechanism called VRS in their next-gen chipsets [AMD 2021; Nvidia 2018; Qualcomm 2021]. One way to reduce blur is to reduce the amount of time a signal is displayed every frame (aka persistence) but this can lead to flicker if the display’s refresh rate is lower than the critical fusion frequency of the HVS and from a lower accuracy of saccadic eye motion [Goettker et al 2020]. When the display’s spatial and temporal sampling frequency is lower than that of the displayed signal, we see aliasing artifacts which are a common occurrence in real-time graphics
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