High-fidelity rendering of complex scenes at interactive rates is one of the primary goals of computer graphics. Since high-fidelity rendering is computationally expensive, perceptual strategies such as visual attention have been explored to achieve this goal. In this paper we investigate how two models of human visual attention can be exploited in a selective rendering system. We examine their effects both individually, and in combination, through psychophysical experiments to measure savings in computation time while preserving the perceived visual quality for a task-related scene. We adapt the lighting simulation system Radiance to support selective rendering, by introducing a selective guidance system which can exploit attentional processes using an importance map. Our experiments demonstrate that viewers performing a visual task within the environment consistently fail to notice the difference between high quality and selectively rendered images, computed in a significantly reduced time.