Visually Lossless Content and Motion Adaptive Shading in Games

We present a technique that adaptively adjusts the shading rate during rendering based on the scene content and motion. Our goal is to improve performance with no loss in perceived quality. We determine per-screen-tile shading rate by testing an error estimate against a perceptually-corrected just-noticeable difference threshold. Our design features an effective and efficient error estimate using spatial and frequency analysis of half and quarter rate shading. We also study the effect of motion in reducing perceived error, a consequence of display-persistence and/or motion blur effects. Our implementation uses the computed per-tile shading rate with variable rate shading (a recent GPU feature) to lower shading cost. We demonstrate the quality and performance of our technique on two high-end game engines and shipped games.