Change here the projection parameters for a single layer or a list of layers.
To modify a layer, click over the graphic area to open a menu and choose a layer,
or write its identification (name and number) on the
Layer entry. To modify
a list of layers, press the button
List (after creating the list of layers
with
Layer->Select). Parameters for empty entries or
Local choices
remain unchanged.
To change a layer name write the new name in the
Layer entry,
followed by the layer number (GAMGI needs the number to identify the layer).
To change the name for a list of layers, press
List first
and then write the new common name in the
Name entry.
Perspective, Orthographic
Change the type of projection of the layer.
GAMGI projects the 3D space on the 2D screen using
Perspective
or
Orthographic projections. The
Perspective projection
is better to simulate realistic views and gives users a depth feedback,
but the
Orthographic projection preserves object dimensions,
as these are not distorted by perspective.
Near, Far, Top
Change the dimensions of the space volume that is visible to the observer,
after being projected into the window graphic area.
This volume has six faces, and the front and back faces are always perpendicular
to the viewing direction.
Near and
Far parameters set
the distance from the view point to these front and back faces, respectively,
corresponding to the minimum and maximum distances that the observer can see.
Near must be smaller than
Far.
In a
Orthographic projection, the projection volume is a rectangular
parallelepiped, so the 4 lateral faces are paralell and perpendicular to
each other. In a
Perspective projection, the projection volume is
a truncated quandrangular pyramid, with the apex at the view point.
Top defines the half-height of the front face of the projection
volume. The width is automatically determined from the ratio height / width
of the window graphic area, so everytime users resize this window, the
projection volume changes accordingly. Increasing
Top increases
the visible volume and decreases the size of the objects.
Each layer has its own projection parameters, so in a window with
multiple visible layers, the image rendered in the graphic area
is the superposition of the various, totally independent, layer
views.