Game Development Reference
In-Depth Information
Figure 1.1. Rendered terrain, with the underlying wireframe mesh partially superim-
Our algorithm was heavily inspired by two existing algorithms. The first in-
spiration came from the great desire to walk through the procedural mountains
created by F. Kenton Musgrave [Ebert et al. 98], in real time. The second in-
spiration came from the visual beauty of the real-time water created by Claes
Johanson, in his introduction of the projected grid concept [Johanson 04]. The
concept helped form one of the ideas for the basis of our subdivision algorithm,
by showcasing effective and ecient vertex placement to display a vast area of
The Algorithm
A few terms are used throughout this paper and are integral to understanding the
general algorithm and the related descriptions. Section 1.2.1 will describe these
terms and provide related calculations. An algorithm overview is provided in
Section 1.2.2 , and Sections 1.2.3 to 1.2.5 d escribe the main separate components
of our algorithm.
1.2.1 Terms and Definitions
Viewable region. A viewable region , denoted by R , is defined as an axis aligned
quadrilateral representing a region that is to be subdivided and/or rendered. This
region is defined from a center position and an applied offset in both the positive
and negative directions along each aligning axis (see Figure 1.2 ). The center
position is denoted by R C . The applied offset is denoted by R λ . The bounding
points of the region are denoted by P 1 , P 2 , P 3 ,and P 4 .
Viewable region span. To quantify a viewable region span , denoted by θ , we defined
the following calculation at point P and applied offset λ :
θ ( P, λ )=
P ScreenR
P ScreenL |
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