Change here the geometry for a single light or a list of lights.
To modify a light, click over the graphic area to open a menu and choose a light,
or write its identification (name and number) on the
Light entry. To modify
a list of lights, press the button
List (after creating the list of lights
with
Light->Select). Parameters for empty entries or
Local choices
remain unchanged.
To change a light name write the new name in the
Light entry,
followed by the light number (GAMGI needs the number to identify the light).
To change the name for a list of lights, press
List first
and then write the new common name in the
Name entry.
Directional
Directional lights emulate lights very far from the objects they
illuminate (as the Sun illuminating the Earth), so: 1) the light
beams can be considered as paralel; 2) the attenuation produced
by the distances between the objects is negligible, compared to
the attenuation produced by the distance from the source (the
intensity of the Sun light iluminating the top of a building
or a street nearby is approximately the same).
Directional lights are thus determined by the
X,
Y,
Z coordinates of the
Direction vector.
Positional
Positional lights emit from a single point into all directions,
with equal intensity. The attenuation in the beam intensity, from the
source to the objects might be already significant (the visibility
produced by street lights decreases rapidly with distance).
Positional lights are thus determined by the
X,
Y,
Z coordinates of the light
Position.
Spot
Spot lights differ from positional lights because they emit in a given
Direction, as in a lamp. The
Angle (beam aperture) between
this
Direction (the spot) and the light outer limit (the cutoff),
can vary between almost 0 degrees (as in a laser) and 90 degrees (as in
a ceilling light).
A spot light is thus determined by its position, direction and angle.
Direction,
Position,
Angle and
Attenuation
entries are automatically enabled or disabled, according to the type of
light selected.