3D unsharp masking for scene coherent enhancement

We present a new approach for enhancing local scene contrast by unsharp masking over arbitrary surfaces under any form of illumination. Our adaptation of a well-known 2D technique to 3D interactive scenarios is designed to aid viewers in tasks like understanding complex or detailed geometric models, medical visualization and navigation in virtual environments. Our holistic approach enhances the depiction of various visual cues, including gradients from surface shading, surface reflectance, shadows, and highlights, to ease estimation of viewpoint, lighting conditions, shapes of objects and their world-space organization. Motivated by recent perceptual findings on 3D aspects of the Cornsweet illusion, we create scene coherent enhancements by treating cues in terms of their 3D context; doing so has a stronger effect than approaches that operate in a 2D image context and also achieves temporal coherence. We validate our unsharp masking in 3D with psychophysical experiments showing that the enhanced images are perceived to have better contrast and are preferred over unenhanced originals. Our operator runs at real-time rates on a GPU and the effect is easily controlled interactively within the rendering pipeline.