max planck institut informatik
A basic principle behind image comprehension is that humans are able to mentally reconstruct an original scenario from visual cues such as shading, occlusions, perspective foreshortening, shadows and specularities. Local contrast enhancement emphasizes these cues, aiding the interpretation of 3D scenes and complex geometry, which is the common task in applications such as medical diagnostics, computer simulations, geographical navigation, game playing and film creation. The main problem is in deciding which cues to emphasize and how to do so with a predictable effect.
The goal of this work is to construct a perceptually founded approach for local contrast enhancement of arbitrary interactive 3D scenes. Such an approach should provide easier shape recognition, better visual separation between objects and a clarification of their spatial arrangement solely by increasing the apparent contrast of specific visual cues. Instead of identifying and modifying cues separately, we look at their common cause, changes (or gradients) in reflected light. These light gradients include all cues caused by variations in surface geometry, material properties, incoming light properties and the spatial arrangement of objects. For example, where a surface receives different amounts of incoming light (possibly in shadow), where reflectance properties change, and where specular highlights occur. In this work we strive to simultaneously increase the contrast of all such gradients without breaking coherence with the depicted scene.
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.
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Tobias Ritschel, Kaleigh Smith, Matthias Ihrke, Thorsten Grosch, Karol Myszkowski, Hans-Peter Seidel
3D Unsharp Masking for Scene Coherent Enhancement
ACM Trans. Graph. 27(3) (Proceedings SIGGRAPH 2008), 2008.
@article{Ritschel:2008:3DUnsharpMasking,
author = {Tobias Ritschel and
Kaleigh Smith and
Matthias Ihrke and
Thorsten Grosch and
Karol Myszkowski and
Hans-Peter Seidel},
title = {{3D Unsharp Masking for Scene Coherent Enhancement}},
journal = {ACM Trans. Graph. (Proc. of SIGGRAPH 2008)},
volume = 27,
number = 3,
year = {2008}
}
M. B. Ihrke, T. Ritschel, K. Smith, T. Grosch, K. Myszkowski, H.-P. Seidel
A Perceptual Evaluation of 3D Unsharp Masking
Proceedings Human Vision and Electronic Imaging XIII, 2009
@inproceedings{Ihrke:2008:3DUnsharpMaskingStudy,
author = {Matthias Ihrke and
Tobias Ritschel and
Kaleigh Smith and
Thorsten Grosch and
Karol Myszkowski and
Hans-Peter Seidel},
title = {A Perceptual Evaluation of 3D Unsharp Masking},
booktitle = {Human Vision and Electronic Imaging XIII},
publisher = {SPIE},
year = {2009}
}