We already mentioned that good visual approximations of trees should display the fringed character of the foliage. If only a few large-sized polygons are used, the desired look is not achieved, not even if partially transparent textures are used. It is more efficient to represent the foliage deliberately using unconnected prim- point-based representation ^ itives. […]
Category: Digital Design of Nature
Static LOD Methods for Trees
The appearance of trees is mostly determined by the foliage, so that methods have to achieve an optimal approximation for the many isolated surfaces of the leaves. The problem here is the special characteristic of the foliage, since, in contrast to smooth surfaces, the approximation should not reveal a smoothness but rather the fringed outline […]
LOD Methods for Smooth Surfaces
The successive simplification of closed, smooth surfaces is the subject of many approaches. Some methods work directly with geometric data; others transform the data into a new representation in which the reduction is executed. A common example is the simplification in wavelet space [53, 209]. The classic method, which works directly with geometric data, is […]
Level-of-Detail
The procedures discussed in the last chapter, and particularly the efficient raytracing implementations, allow for a relatively fast, though sufficiently exact calculation of the light distribution in complex botanical scenes. The performance of the procedures is here mostly only restricted through the quantities of the data that have to be processed. However, it is not […]
When Do Computer Images Appear Real?
In concluding this chapter, some questions remain when viewing images, such as those on the following pages. Why is it actually possible to reproduce using relatively simple methods a sometimes astonishing degree of realism? One reason could possibly be the relatively simple lighting conditions within the plants that are easy to approximate using traditional computer […]
Plant Images Using Radiosity
In the rendering of landscapes, radiosity has so far rarely been used. The enormous amount of geometric information causes extreme computing times and needs a huge amount of memory. Soler and Sillion [204] decreased this by integrating hierarchical instancing in radiosity procedures (see Sect. 8.5). hierarchical radiosity ^ With the hierarchical version of the algorithms, […]
Accelerated Ray Query with Index Images
The method described here takes advantage of the fact that in plant scenes very seldomly must reflection rays be traced. A great part of the ray query thus consists of the so called primary rays, and the number of secondary rays caused by reflection is minimal. All primary rays start at the viewing point of […]
Plant Images Using Raytracing
As already mentioned, raytracing is the most widely used method for the simulation of global illumination. With the described spatial division methods and bounding objects, the time-consuming process of the ray query can be optimized. Additional optimizations can be reached with special versions of raytracing that are described in the following. First two aspects for […]
Occlusion Culling
The term “occlusion culling” defines methods that exclude all the objects hidden by other objects before the actual image computation. In connection with local rendering methods, these objects are not even transferred to the graphics hardware. In connection with raytracing, these procedures are used to decrease the total complexity of the scene description, and to […]
Bounding Boxes
In raytracing, a great amount of computing time must be spent on the so-called ray query. Here, with each tracing ray, we have to check which object or polygon of the scene is hit first. On the other hand, in local illumination models a lot of work is due to the visibility calculation, which defines […]