3D unsharp masking for scene coherent enhancement

Abstract

Figure 1: A naturally illuminated 3D scene (left) and the same scene with 3D unsharp masking enhancement (center). Our enhancement technique is coherent with the scene itself, not simply with each rendered frame, permits arbitrary lighting and is temporally coherent. AbstractWe 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.

Perceptually based downscaling of images

“…This ratio thus adaptively adjusts the filter using H as the reference image so as to preserve the local features. Unsharp masking combined with pixel-wise contrast measures extracted from a reference image has previously generated excellent results for enhancing images generated by tone mapping [Krawczyk et al 2007] [Ritschel et al 2008]. It is interesting to see that our SSIM-optimal filter leads to a similar term for the downscaling problem.…”

Light warping for enhanced surface depiction

“…Besides, it requires a time-consuming pre-process and yet does not incorporate automatic simplification behaviors as opposed to our approach. Compared to [Ritschel et al 2008], our system offers a greater control as it enhances the surface features uniformly, while 3D unsharp masking increases indiscriminately radiance contrast, resulting in irregular enhancement and alteration of material properties. Our approach is also simpler to control compared to previous work, as it offers 3 intuitive parameters: warping magnitude α, lighting contrast γ, and feature scale s.…”

Realtime shape-enhanced shading of large scale skinned meshes with fast normal updating

“…However, as these method do not separate the analysis and shading step, they have limited control in surface feature depiction, and use rather smooth shading variations to convey concavities. The 3D unsharp masking technique of Ritshel et al [8] is also related to such volumetric enhancement of shape, and thus shares the advantages and drawbacks of the aforementioned methods. Some researchers chose to modify reflection rules according to the local surface information: Gooch et al [22] reproduce effects used in technical illustrations of mechanical parts; mean-curvature shading technique by Kindlmann et al [23] resembles pen-and-ink archeological illustrations; normal enhancement by Cignoni et al [10] is inspired from technical pencil drawings; exaggerated shading by Rusinkiewicz et al [12] uses a set of rules originating from cartography; geometry-dependent lighting [13] is inspired from anatomical illustration, and apparent relief by Vergne et.…”

“…Besides, it is clearly not always wanted, the preservation of material and illumination information is expected in many situations. Many researchers thus turn to study various shading model which can selectively amplifying or suppressing surface details to enhance the features and convey better visual interpretation of the shape [8], [9], [10], [11], [12], [13], [14], [15], [16]. However, many of them are still limited by the performance *Corresponding author: Juncong Lin, jclin@xmu.edu.cn and can not satisfy the requirement of real-time applications.…”