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# Full text

Title
The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics
Author
Chen, Jun

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
411
Figure 2 Surface model of timber component
3. Simulation of lignification
In order to generate satisfactory and virtual realistic images of
a timber building by the computer simulation system, it needs
to simulate the surface material of each component besides
the establishment of correct model. This is beginning with the
generation of material texture.
3.1 Generating material texture
The main task of generating material texture is to determine
the color, texture and light and shade pattern of the material.
The color of a material can be divided into three categories:
ambient the color of the shading part of an object,
diffuse—-the color of an object under lighting, specular—-the
color of an object under strong lighting.
Texture describes the natural characteristics of the
surface of an object, it can be generated by a 2D random
function f(u,v) Let N(p,a) denotes a normal distribution
function withprepresents the mean value and crthe standard
deviation. The method generates f(u,v) is the following:
/ (« min
/ (“ min
/ (“ max
. / (“ max
Vmm )= /, = N (0 Vmax )= /2 = N(0 a) O)
v mi „ )= /3 = N (0 a)
Vmax )= /4 = ^(0 G)
therefore, the generation of a random function upon the
interval of [u-min, u-max]*[v-min, v_max] can be decomposed
to the generation of 4 random functions upon 4 sub-intervals
derived from the segmentation of the whole interval into 4 parts,
with the cut-off point on (....). A recursive process is applied by
using the abovementioned algorithm until the detail of the
generated texture is satisfactory enough. According to the
formula listed in equation 1 and 2, the standard deviation is