BENDING TYPE TO REPRESENT THE THIRD DIMENSION OF TERRAIN ON MAPS

Bernhard JENNY

ABSTRACT: Many 3D maps show type with considerable distortion, resulting from draping 2D maps directly onto digital elevation models. Distortion is caused by perspective foreshortening and by the irregular shape of the terrain surface. Characters are compressed, expanded, skewed, occluded and misaligned, producing distorted text labels that are difficult or even impossible to read. However, deformed type can also function as a visual clue indicating the shape of the terrain. When rendered in a perspective view, draped text labels traverse hills and valleys along curved lines. The curviness of these lines reflect the shape of the terrain. This paper draws inspiration from this observation encountered on 3D maps, and replicates this effect for standard 2D orthogonal maps. Type deformed in this way not only provides textual information, but also suggests the third dimension of the terrain. A method is presented that bends text along a curved line following the terrain. The line is extracted from a digital elevation model. The amount and direction of bending can be controlled by a user-definable parameter. The more the label is bent, the closer it follows the undulations of the terrain and better portrays the shape of the terrain, but the more difficult it is to read.

Keywords: Terrain mapping, label placement, lettering for areal features.

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