2007 | 5 Themenheft

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Image Morphology: From Perception to Rendering
Buf, Hans Du; Rodrigues, Joao (2007) , S. 98-116
A complete image ontology can be obtained by formalising a top-down meta-language which must address all possibilities, from global message and composition to objects and local surface properties. In computer vision, where one general goal is image understanding, one starts with a bunch of pixels. The latter is a typical example of bottom-up processing, from pixels to objects to layout and gist. Both top-down and bottom-up approaches are possible, but can these be unified? As it turns out, the answer is yes, because our visual system does it all the time. This follows from our progress in developing models of the visual system, and using the models in re-creating an input image in the form of a painting.
Specification of Morphological Models with L-Systems and Relational Growth Grammars
Kurth, Winfried (2007) , S. 50-79
Among the techniques for the creation of photorealistic virtual organisms, particularly plants, and in scientific models of vegetation structure, rule-based specifications (formal grammars) play a prominent role. Lindenmayer systems (L-systems) are the most widespread formalism of this sort, but certain types of graph grammars, combined with standard object-oriented programming, offer even more possibilities to specify rule-driven developments of 3-dimensional arrangements, morphology of virtual organisms and underlying processes like, e.g., metabolic reactions. Examples of grammar rules and the virtual geometrical structures generated from them, all realizable with the open-source software GroIMP (www.grogra.de), are shown. This grammar-based approach is often not immediately used for the direct specification of a picture as a pattern of graphical elements in a plane, but for virtual 3-D scenes, which are then rendered visible using standard techniques of geometry- based computer graphics.
A Survey of Image-Morphologic Primitives in Non-Photorealistic Rendering
Isenberg, Tobias (2007) , S. 80-97
This paper presents an overview of the image-morphologic primitives used commonly in non-photorealistic rendering (NPR), a subdomain of computer graphics that is inspired by a long tradition of artistic and illustrative depiction. In particular, we survey NPR shading, stroke-based rendering, sparse line drawings, graftals, and area primitives. Such primitives usually cover larger regions on the canvas and often carry a meaning beyond the color of the image region they represent. This distinguishes them from the pixel as a primitive used in photorealistic rendering, which does not have any meaning aside from sampling the color of the image section it represents. We give examples to illustrate the individual techniques and briefly mention how they are tracked though the rendering process as well as represented in the final image.
Syntactic Structures in Graphics
Engelhardt, Yuri (2007) , S. 23-35
Building upon the existing literature, we are suggesting to regard the building blocks of all graphics as falling into three main categories: a) the graphic objects that are shown (e.g. a dot, a pictogram, an arrow), b) the meaningful graphic spaces into which these objects are arranged (e.g. a geographic coordinate system, a timeline), and c) the graphic properties of these objects (e.g. their colors, their sizes). We suggest that graphic objects come in different syntactic categories, such as nodes, labels, frames, links, etc. Such syntactic categories of graphic objects can explain the permissible spatial relationships between objects in a graphic representation. In addition, syntactic categories provide a criterion for distinguishing meaningful basic constituents of graphics. Based on the above, we discuss how the concept of syntactics can be applied to graphics. Finally we distinguish different types of meaningful graphic spaces that can be used to construct graphics. Throughout the paper we relate our proposals to the relevant existing literature.

Browsing 2007 | 5 Themenheft by Subject "Computergrafik"

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