Achieving realistic results is one of the most important goals in outdoor Mixed Reality (MR) applications that are built by merging virtual objects into real scenes. One kind of these applications consists on viewing a virtual object that is distant from the observer. The objective in such applications is to realistically represent the atmospheric effect over the appearance of the virtual object. This natural effect over objects in open air scenes is known as aerial perspective and causes the color of distant objects to become fainter and shift towards the environmental light color. However, aerial perspective modeling is challenging since outdoor illumination is unpredictable and continually changing. In computer vision (CV) and computer graphics (CG), light scattering phenomena causing the aerial perspective effect are generally modeled by a combination of a directly transmitted light and an airlight. Using such model, several studies have been carried out for aerial perspective rendering in complete-virtual applications, but only Zhao 4 have presented a research applied to MR. His approach employs a straightforward adaption of Preetham's CG-directed aerial perspective model 2; however, his implementation is a computer-intensive task. In this paper, we propose an improved scattering model for MR applications that is based on both a full visible spectrum of light analysis and an atmospheric turbidity estimation. Our method first estimates the atmospheric turbidity by matching the brightness distributions of a captured omnidirectional image and sky models. Then the estimated turbidity is utilized to render the aerial perspective effect as a summation of the direct transmission and the airlight.
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