Section 8.4 Reduction of the Geometric Data   image quantization   median cut algorithm   • : •   Figure 8.8 Median cut algorithm: (a) initial partitioning at the median regarding ж-values; (b) areas after a number of divisions with representatives (red panes) at the center of gravity of all points in a box   (a)   (b)   At the beginning of the procedure, the number of areas is defined. After respec­tively many areas have been generated, the representative is positioned at the centroid of all the points in an area. In a plant population, the representative is thus assigned the attribute and thereby also the respective appearance resulting from the centroid element. Figure 8.8 demonstrates this process. &nbsp

Chapters Hierarchical Instancing

Modeling Vegetation

Instancing can take place on several levels. Thus not only can different plants be represented over a single geometry, but instancing can also be implemented within tree structures: Leaf instancing is used to define a small branch; branch instancing is applied to define a larger branch, and so on. This way, optimal compression is achieved for the geometry of a tree.

The concept can be extended in that for each instancing object several represen­tatives are generated to increase the variability of the total geometry. This step was applied in [132] in order to simplify an image-based rendering method.