Constrained optimization for disoccluding geographic landmarks in 3D urban maps

Abstract

Figure 1: Side-by-side comparison between an ordinary perspective view (left) and its optimally distorted version with our approach (right). Note that we can successfully avoid the occlusions of important route to the destination (drawn in orange) while accentuating the 3D appearance of the landmark buildings. ( ABSTRACTIn composing hand-drawn 3D urban maps, the most common design problem is to avoid overlaps between geographic features such as roads and buildings by displacing them consistently over the map domain. Nonetheless, automating this map design process is still a challenging task because we have to maximally retain the 3D depth perception inherent in pairs of parallel lines embedded in the original layout of such geographic features. This paper presents a novel approach to disoccluding important geographic features when creating 3D urban maps for enhancing their visual readability. This is accomplished by formulating the design criteria as a constrained optimization problem based on the linear programming approach. Our mathematical formulation allows us to systematically eliminate occlusions of landmark roads and buildings, and further controls the degree of local 3D map deformation by devising an objective function to be minimized. Various design examples together with a user study are presented to demonstrate the robustness and feasibility of the proposed approach.

Occlusion-Free Visualization of Important Geographic Features in 3D Urban Environments

“…Recently, deformation methods [5,18,19] have been proposed to alleviate occlusions in urban areas. Deformation methods clear the line of sight by deforming the occluding objects and the surroundings.…”

“…Deng et al [18] presented an automatic method that enabled an interactive context-aware visualization of the relevant urban features. Hirono et al [5] proposed an optimization method based on common aesthetic criteria to disocclude landmarks for urban environments. However, this optimization does not support the interactivity required for various tasks.…”

“…However, the perturbation of spatial relationships caused by this camera-centric approach is a major concern. Hirono et al [5] presented a method to enhance map readability that can identify common design criteria often employed in hand-drawn illustrative maps created by cartographic artists. This method employed fixed orientation, relative position, and scale limits to maintain consistency in the arrangement of geographic features and formulated these as hard constraints, while introducing minimum displacement and occlusion avoidance as a nuanced approach to enhance the reality and readability of 3D urban maps, respectively.…”

“…Third, the realism of the 3D environment is lost. A 2D map cannot provide depth information; thus, it fails to yield a visual match to the real landscapes people see in their daily lives [5].…”

“…Therefore, users cannot obtain the spatial information concerning the route and, consequently, will not be able to make good advance preparations for upcoming turns or intersections. It is challenging to eliminate occlusions of important geographic features while simultaneously preserving the global layout of a 3D map [9]; Hirono et al [5]. Moreover, rendering such an occlusion-free view consumes considerable computational resources.…”