Exploring Transition Textures for Pseudo-natural Maps

Pseudo-natural maps show land cover information in a compelling style that combines cartographic abstraction with natural appearance. To make this style available to the modern cartographer, a (semi-) automatic method that generates pseudo-natural textures for rendering land cover categories on maps would be helpful. This article focuses on a single aspect of pseudo-natural map creation, namely the generation of gradual, natural looking transitions between land cover categories, so called transition textures. We give a survey on how texture synthesis algorithms are used in computer graphics to handle transitions between textures and point out how they could be useful for creating textured maps. By pointing out promising approaches, we aim to contribute to the development of (semi-) automatic methods for the generation of textured pseudo-natural maps in 2D and 3D for static perspective views. 1 Pseudo-realistic Maps A sterile, technical style as shown in Figure 1 (left) is the look most people associate with topographic maps. Yet, cartographic representations of the landscape have been created in more compelling styles that provide the observer with an attention-gripping, immersive experience. We call this map style pseudo-natural because it combines natural appearance with cartographic abstraction. Examples of such maps are natural-colour relief maps and winter maps in 2D, or hand-painted panorama maps in 3D (Figure 1, right). Important and well-known 20 century cartographic artists that we consider to have created pseudo-natural maps include, for example, Hal Shelton (USA), Richard E. Harrison (USA), and Heinrich C. Berann (Austria); contemporary artists include Tibor Tóth (USA), Arne Rohweder (Switzerland), Winfried Kettler (Switzerland) and James Niehues (USA). Most pseudo-natural maps of high quality were created manually, either by using traditional pens and brushes, or by applying digital-manual tools (e.g. digital paint brushes). Pseudo-natural design can be applied to maps with traditional two-dimensional map projections, or panoramic 3D maps. Using standard graphics editing software (e.g. Adobe Photoshop), pseudo-natural maps can be generated that combine characteristics of aerial photography, computer-generated textures and/or standard topographic map elements to depict land cover information in pseudo-natural look (Figure 2).