Figure 3: Rendering with acessories from the library People for People 
Wave information can produce the effect of uneven 
surfaces and have influence to light refelection. 
Light modells. The following parameters have to be 
considered when targeting to a realistic presentation: 
The colour of the object itself (the diffuse colour), 
surface properties, reflections, shadows , light colours 
and the light sources. 
The light model in general is a result of three different 
types. Ambient light, diffuse light, specular light. The 
colour of an object depends on the influence of these 
light forms at one point of time. 
Ambient light is the the illumination of a scene and 
provides the basic colour. There's no specific source 
for ambient light. Therefore the ambient colour for an 
object is constant. This light's intensity does not dimi- 
nish with distance. 
Diffuse light is reflected from object surfaces. Non 
glossy objects reflect light in all directions. One can 
observe from an arbitrary position the same intensity 
for a special point. Diffuse light is only dependent from 
176 
the light position relative to the observer. 
Intensity results from the angle between light direction 
and surface normal vector. Intensity decreases with 
larger angles. 
The specular component reproduces the bright shi- 
ning light, accepted from a billard ball. Specular light is 
the light of a light source beeing reflected directly to 
the viewer.The highest intensity occurs when the 
viewing direction fits the direction of reflection, otherwi- 
se it decreases rapidly. 
AccuRender contains a vast an flexible set of ligt 
modelling tools. Among them are apart from ambient 
light a distant light, point light, spot light and focuses 
spot light as well as parallel light in a linear and rec- 
tangular light source. Light sources ar in general invisi- 
ble but can be visualized in a transparent body. 
Properties of anly light source are the intensity , sha- 
dow and penumbra, the position and the light colour. 
With exeption of distant and indirect light, a light sour- 
ce looses intensity by distance, either invers linar or 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
invers squar 
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