2009

The item selected will depend on your Selection Resolution setting. See “ Selection Resolution ”
for more information.
or
• Right-click an item in the Selection Tree (see “ Selection Trees ” for more information), click Presenter
on the shortcut menu, and then choose the shadow casting option you require.
Advanced Lighting
NavisWorks Presenter is capable of many advanced lighting effects, including soft shadows, physically
accurate lighting simulation, volumetric lighting effects and Image-based lighting.
Soft Shadows
NavisWorks Presenter includes shadows generated from pre-calculated shadow-maps for each shadow
casting light source. The use of shadow maps enables rapid rendering of shadows with soft or graduated
edges. The shadow resolution can be controlled to balance performance and image quality.
Soft shadows are only suitable for use with small models and are disabled by default. For large models
the generation of the shadow maps can use excessive amounts of time and memory. Soft shadows
generated for large models are often too vague and dispersed without using an excessively high
resolution, which uses even more memory and time.
Physically Accurate Lights
By default Presenter uses lights with unitless, or empirical intensities. These are physically meaningless
and are just chosen to give a visually pleasing result. Presenter can also use physically accurate
intensities. These are defined in real world units such as Candela, Lumen or Lux. However, once we start
using lights with real world intensities, we start to produce images with a real world variation in luminance
values.
By default Presenter uses lights whose intensity remains constant as you move further from the light. In
the real world intensity is reduced proportional to the inverse square of the distance from the light.
Changing a light's "Fall Off" parameter to "Inverse Square Law" will more accurately model a light's fall off
in intensity. However, once we start using lights with real world fall off, we start to produce images with a
real world variation in luminance values.
In the real world, the human eye is capable of resolving images in extremely varied lighting conditions,
ranging from bright sunshine reflecting off snow to a room lit only by a single candle. In computer graphics
on the other hand, we need to produce an image on a display device which has a very limited range of
luminance values. Therefore it is necessary to compress the range of luminance values found in a real
world scene into the displayable range in such a way as to produce a realistic looking image.
Photography, of course, has exactly the same problem. If a photographer (or camera) does not take into
account the light levels in a scene before calculating the exposure of the shot, the likely result will be an
image which is either over-exposed (everything is too bright) or under-exposed (everything is too dark). A
professional photographer will also use different speeds of film for different lighting conditions. The aim is
to produce an image on film that is representative of how that scene would have looked to a human
observer.
Presenter includes an "Auto Exposure" option (see “ Auto Exposure ”). When enabled, Presenter will
Presenter Lighting
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