Abstract: A nonisotropic hybrid image/model-based gaze-contingent rendering technique utilizing ray casting on a GPU is discussed. Empirical evidence derived from human subject experiments indicates an inverse relationship between a peripherally degraded scene's high-resolution inset size and mean search time, a trend consistent with existing image-based and model-based techniques. In addition, the data suggest that maintaining a target's silhouette edges decreases search times when compared to targets with degraded edges. However, analysis suggests a point of diminishing returns with an inset larger than 15$deg $ when target discrimination is a component of visual search. Benefits of the hybrid technique include simplicity of design and parallelizability, both conducive to GPU implementation.