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662 lines
20 KiB
662 lines
20 KiB
The Open Scene Graph library, which current FlightGear uses for its 3D
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graphics, provides excellent support for multiple views of a
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scene. FlightGear uses the osgViewer::Viewer class, which implements a
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"master" camera with "slave" cameras that are offset from the master's
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position and orientation. FlightGear provides the "camera group"
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abstraction which allows the configuration of slave cameras via the
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property tree.
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Slave cameras can be mapped to windows that are open on different
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screens, or all in one window, or a combination of those two schemes,
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according to the video hardware capabilities of a machine. It is not
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advisable to open more than one window on a single graphics card due
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to the added cost of OpenGL context switching between the
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windows. Usually, multiple monitors attached to a single graphics card
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are mapped to different pieces of the same desktop, so a window can be
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opened that spans all the monitors. This is implemented by Nvidia's
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TwinView technology and the Matrox TripleHead2Go hardware.
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The camera group is configured by the /sim/rendering/camera-group node
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in the property tree. It can be set up by, among other things, XML in
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preferences.xml or in an XML file specified on the command line with
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the --config option.
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Here are the XML tags for defining camera groups.
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camera-group
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For the moment there can be only one camera group. It can contain
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window, camera, or gui tags.
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window
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A window defines a graphics window. It can be at the camera-group
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level or defined within a camera. The window contains these tags:
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name - string
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The name of the window which might be displayed in the window's
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title bar. It is also used to refer to a previously defined
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window. A window can contain just a name node, in which case
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the whole window definition refers to a previously defined window.
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host-name - string
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The name of the host on which the window is opened. Usually this is
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empty.
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display - int
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The display number on which the window is opened.
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screen - int
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The screen number on which the window is opened.
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x, y - int
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The location on the screen at which the window is opened. This is in
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the window system coordinates, which usually puts 0,0 at the upper
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left of the screen XXX check this for Windows.
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width, height - int
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The dimensions of the window.
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decoration - bool
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Whether the window manager should decorate the window.
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fullscreen - bool
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Shorthand for a window that occupies the entire screen with no
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decoration.
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camera
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The camera node contains viewing parameters.
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window
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This specifies the window which displays the camera. Either it
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contains just a name that refers to a previous window definition, or
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it is a full window definition.
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viewport
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The viewport positions a camera within a window. It is most useful
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when several cameras share a window.
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x, y - int
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The position of the lower left corner of the viewport, in y-up
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coordinates.
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width, height - int
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The dimensions of the viewport
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physical-dimensions
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The physical dimension of the projection surface.
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Use this together with the master-perspective, right-of-perspective
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left-of-perspective, above-perspective, below-perspective or
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reference-points-perspective
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width, height - double
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The dimensions of the projection plane, if unset the veiwport values
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are taken as default.
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bezel
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Gives informantion about the bezel of monitors for a seamless view.
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right
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right bezel with in the same units than with and height above
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left
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left bezel with in the same units than with and height above
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top
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top bezel with in the same units than with and height above
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bottom
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bottom bezel with in the same units than with and height above
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view
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The view node specifies the origin and direction of the camera in
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relation to the whole camera group. The coordinate system is +y up,
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-z forward in the direction of the camera group view. This is the
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same as the OpenGL viewing coordinates.
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x,y,z - double
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Coordinates of the view origin.
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heading-deg, pitch-deg, roll-deg - double
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Orientation of the view in degrees. These are specified using the
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right-hand rule, so a positive heading turns the view to the left,
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a positive roll rolls the view to the left.
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perspective
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This node is one way of specifying the viewing volume camera
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parameters. It corresponds to the OpenGL gluPerspective function.
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fovy-deg - double
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The vertical field-of-view
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aspect-ratio - double
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Aspect ratio of camera rectangle (not the ratio between the
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vertical and horizontal fields of view).
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near, far - double
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The near and far planes, in meters from the camera eye point. Note
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that FlightGear assumes that the far plane is far away, currently
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120km. The far plane specified here will be respected, but the sky
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and other background elements may not be drawn if the view plane is
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closer than 120km.
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fixed-near-far - bool
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If true the near and far values are taken from above, if false
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near and far are adapted from the scene and visibility.
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Defaults to true.
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offset-x, offset-y - double
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Offsets of the viewing volume specified by the other parameters in
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the near plane, in meters.
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frustum
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This specifies the perspective viewing volume using values for the near
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and far planes and coordinates of the viewing rectangle in the near
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plane.
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left, bottom - double
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right, top - double
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The coordinates of the viewing rectangle.
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near, far - double
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The near and far planes, in meters from the camera eye point.
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fixed-near-far - bool
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If true the near and far values are taken from above, if false
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near and far are adapted from the scene and visibility.
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Defaults to true.
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ortho
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This specifies an orthographic view. The parameters are the sames as
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the frustum node's.
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fixed-near-far - bool
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If true the near and far values are taken from above, if false
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near and far are adapted from the scene and visibility.
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Defaults to true.
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master-perspective
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Defines a persective projection matrix for use as the leading display
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in a seamless multiscreen configuration. This kind of perspective
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projection is zoomable.
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eye-distance - double
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The distance of the eyepoint from the projection surface in units of
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the physical-dimensions values above.
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x-offset, y-offset - double
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Offset of the eyelpint from the center of the screen in units of
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the physical-dimensions values above.
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left-of-perspective, right-of-perspective, above-perspective,
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below-perspective
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Defines a perspective projection matrix for use as derived display
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in a seamless multiscreen configuration. The projection matrix
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is computed so that the respective edge of this display matches the
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assiciated other edge of the other display. For example the right edge
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of a left-of-perspective display matches the left edge of the parent
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display. This also works with different zoom levels, leading to distorted
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but still seamless multiview configurations.
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The bezel with configured in the physical dimensions of this screen and
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the parent screen are taken into account for this type of projection.
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parent-camera - string
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Name of the parent camera.
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reference-points-perspective
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Defines a perspective projection matrix for use as derived display
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in a seamless multiscreen configuration. This type is very similar to
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left-of-perspective and friends. It is just a more flexible but less
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convenient way to get the same effect. A child display is configured
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by 2 sets of reference points one in this current camera and one in
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the parrent camera which should match in the final view.
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parent-camera - string
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Name of the parent camera.
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this
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reference points for this projection.
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point - array of two points
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x, y - double
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x and y coodinates of the reference points in units of this
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physical-dimensions.
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parent
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reference points for the parent projection.
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point - array of two points
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x, y - double
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x and y coodinates of the reference points in units of the
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parents physical-dimensions.
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texture
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This tag indicates that the camera renders to a texture instead of the
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framebuffer. For now the following tags are supported, but obviously
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different texture formats should be specified too.
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name - string
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The name of the texture. This can be referred to by other cameras.
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width, height - double
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The dimensions of the texture
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panoramic-distortion
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This tag cause the camera to create distortion geometry that
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corrects for projection onto a spherical screen. It is equivalent to
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the --panoramic-sd option to osgviewer.
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texture - string
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The name of a texture, created by another camera, that will be
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rendered on the distortion correction geometry.
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radius - double
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Radius of string
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collar - double
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size of screen collar.
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gui
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This is a special camera node that displays the 2D GUI.
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viewport
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This specifies the position and dimensions of the GUI within a
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window, *however* at the moment the origin must be at 0,0.
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Here's an example that uses a single window mapped across 3
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displays. The displays are in a video wall configuration in a
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horizontal row.
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<PropertyList>
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<sim>
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<rendering>
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<camera-group>
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<window>
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<name>wide</name>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>0</screen>
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<width>3840</width>
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<height>1024</height>
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<decoration type = "bool">false</decoration>
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</window>
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<camera>
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<window>
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<name>wide</name>
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</window>
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<viewport>
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<x>0</x>
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<y>0</y>
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<width>1280</width>
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<height>1024</height>
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</viewport>
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<view>
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<heading-deg type = "double">0</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>-.5004</left>
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<right>-.1668</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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</camera>
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<camera>
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<window>
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<name type="string">wide</name>
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</window>
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<viewport>
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<x>1280</x>
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<y>0</y>
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<width>1280</width>
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<height>1024</height>
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</viewport>
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<view>
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<heading-deg type = "double">0</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>-.1668</left>
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<right>.1668</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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</camera>
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<camera>
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<window>
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<name>wide</name>
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</window>
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<viewport>
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<x>2560</x>
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<y>0</y>
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<width>1280</width>
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<height>1024</height>
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</viewport>
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<view>
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<heading-deg type = "double">0</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>.1668</left>
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<right>.5004</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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</camera>
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<gui>
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<window>
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<name type="string">wide</name>
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</window>
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</gui>
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</camera-group>
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</rendering>
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</sim>
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</PropertyList>
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Here's a complete example that uses a seperate window on each
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display. The displays are arranged in a shallow arc with the left and
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right displays at a 45.3 degree angle to the center display because,
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at the assumed screen dimensions, the horizontal field of view of one
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display is 45.3 degrees. Each camera has its own window definition;
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the center window is given the name "main" so that the GUI definition
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can refer to it. Note that the borders of the displays are not
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accounted for.
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<PropertyList>
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<sim>
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<rendering>
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<camera-group>
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<camera>
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<window>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>0</screen>
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<fullscreen type = "bool">true</fullscreen>
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</window>
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<view>
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<heading-deg type = "double">45.3</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>-.1668</left>
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<right>.1668</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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</camera>
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<camera>
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<window>
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<name type="string">main</name>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>1</screen>
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<fullscreen type = "bool">true</fullscreen>
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</window>
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<view>
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<heading-deg type = "double">0</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>-.1668</left>
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<right>.1668</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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</camera>
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<camera>
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<window>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>2</screen>
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<fullscreen type = "bool">true</fullscreen>
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</window>
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<view>
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<heading-deg type = "double">-45.3</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>-.1668</left>
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<right>.1668</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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</camera>
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<gui>
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<window>
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<name type="string">main</name>
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</window>
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</gui>
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</camera-group>
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</rendering>
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</sim>
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</PropertyList>
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This example renders the scene for projection onto a spherical screen.
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<PropertyList>
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<sim>
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<rendering>
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<camera-group>
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<camera>
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<window>
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<name type="string">main</name>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>0</screen>
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<!-- <fullscreen type = "bool">true</fullscreen>-->
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<width>1024</width>
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<height>768</height>
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</window>
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<view>
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<heading-deg type = "double">0</heading-deg>
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</view>
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<frustum>
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<top>0.133</top>
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<bottom>-0.133</bottom>
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<left>-.1668</left>
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<right>.1668</right>
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<near>0.4</near>
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<far>120000.0</far>
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</frustum>
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<texture>
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<name>mainview</name>
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<width>1024</width>
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<height>768</height>
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</texture>
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</camera>
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<camera>
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<window><name>main</name></window>
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<ortho>
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<top>768</top>
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<bottom>0</bottom>
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<left>0</left>
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<right>1024</right>
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<near>-1.0</near>
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<far>1.0</far>
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</ortho>
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<panoramic-spherical>
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<texture>mainview</texture>
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</panoramic-spherical>
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</camera>
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<gui>
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<window>
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<name type="string">main</name>
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</window>
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</gui>
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</camera-group>
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</rendering>
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</sim>
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</PropertyList>
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Here is an example for a 3 screen seamless zoomable multiscreen
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configuration using 3 533mmx300mm displays each with a 23mm bezel.
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The side views are angled with 45 deg.
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The commented out reference-points-perspective shows the
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aequivalent configuration than the active right-of-perspective.
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This is done by just using two reference points at the outer
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edge of the bezel of the respective display.
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<PropertyList>
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<sim>
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<view n="0">
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<config>
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<pitch-offset-deg>0.0</pitch-offset-deg>
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</config>
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</view>
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<rendering>
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<camera-group>
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<window>
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<name type="string">0.0</name>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>0</screen>
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<fullscreen type="bool">true</fullscreen>
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</window>
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<window>
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<name type="string">0.1</name>
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<host-name type="string"></host-name>
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<display>0</display>
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<screen>1</screen>
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<fullscreen type="bool">true</fullscreen>
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</window>
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<camera>
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<name type="string">CenterCamera</name>
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<window>
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<name>0.0</name>
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</window>
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<viewport>
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<x>0</x>
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<y>0</y>
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<width>1920</width>
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<height>1080</height>
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</viewport>
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<view>
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<heading-deg type="double">0.0</heading-deg>
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<roll-deg type="double">0.0</roll-deg>
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<pitch-deg type="double">0.0</pitch-deg>
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</view>
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<physical-dimensions>
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<!-- The size of the projection plane: 533mm 300mm -->
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<width>533</width>
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<height>300</height>
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<bezel>
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<right>23</right>
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<left>23</left>
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<top>23</top>
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<bottom>23</bottom>
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</bezel>
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</physical-dimensions>
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<master-perspective>
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<!-- Cheating, the real distance is about 800mm.
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But then the screen does not show what is needed to fly.
|
|
By shortening this pictures get bigger but the view also gets
|
|
less realistic.
|
|
-->
|
|
<eye-distance>450</eye-distance>
|
|
<x-offset>0</x-offset>
|
|
<y-offset>130</y-offset>
|
|
</master-perspective>
|
|
</camera>
|
|
<camera>
|
|
<name type="string">RightCamera</name>
|
|
<window>
|
|
<name>0.0</name>
|
|
</window>
|
|
<viewport>
|
|
<x>1920</x>
|
|
<y>0</y>
|
|
<width>1920</width>
|
|
<height>1080</height>
|
|
</viewport>
|
|
<view>
|
|
<heading-deg type="double">-45</heading-deg>
|
|
<roll-deg type="double">0</roll-deg>
|
|
<pitch-deg type="double">0</pitch-deg>
|
|
</view>
|
|
<physical-dimensions>
|
|
<!-- The size of the projection plane: 533mm 300mm -->
|
|
<width>533</width>
|
|
<height>300</height>
|
|
<bezel>
|
|
<right>23</right>
|
|
<left>23</left>
|
|
<top>23</top>
|
|
<bottom>23</bottom>
|
|
</bezel>
|
|
</physical-dimensions>
|
|
<right-of-perspective>
|
|
<parent-camera type="string">CenterCamera</parent-camera>
|
|
</right-of-perspective>
|
|
<!-- <reference-points-perspective> -->
|
|
<!-- <parent-camera type="string">CenterCamera</parent-camera> -->
|
|
<!-- <parent> -->
|
|
<!-- <point n="0"> -->
|
|
<!-- <x>289.5</x> -->
|
|
<!-- <y>100</y> -->
|
|
<!-- </point> -->
|
|
<!-- <point n="1"> -->
|
|
<!-- <x>289.5</x> -->
|
|
<!-- <y>-100</y> -->
|
|
<!-- </point> -->
|
|
<!-- </parent> -->
|
|
<!-- <this> -->
|
|
<!-- <point n="0"> -->
|
|
<!-- <x>-289.5</x> -->
|
|
<!-- <y>100</y> -->
|
|
<!-- </point> -->
|
|
<!-- <point n="1"> -->
|
|
<!-- <x>-289.5</x> -->
|
|
<!-- <y>-100</y> -->
|
|
<!-- </point> -->
|
|
<!-- </this> -->
|
|
<!-- </reference-points-perspective> -->
|
|
</camera>
|
|
|
|
<camera>
|
|
<name type="string">LeftCamera</name>
|
|
<window>
|
|
<name>0.1</name>
|
|
</window>
|
|
<viewport>
|
|
<x>0</x>
|
|
<y>0</y>
|
|
<width>1920</width>
|
|
<height>1080</height>
|
|
</viewport>
|
|
<view>
|
|
<heading-deg type="double">45</heading-deg>
|
|
<roll-deg type="double">0</roll-deg>
|
|
<pitch-deg type="double">0</pitch-deg>
|
|
</view>
|
|
<physical-dimensions>
|
|
<!-- The size of the projection plane: 533mm 300mm -->
|
|
<width>533</width>
|
|
<height>300</height>
|
|
<bezel>
|
|
<right>23</right>
|
|
<left>23</left>
|
|
<top>23</top>
|
|
<bottom>23</bottom>
|
|
</bezel>
|
|
</physical-dimensions>
|
|
<left-of-perspective>
|
|
<parent-camera type="string">CenterCamera</parent-camera>
|
|
</left-of-perspective>
|
|
</camera>
|
|
<gui>
|
|
<window>
|
|
<name type="string">0.0</name>
|
|
</window>
|
|
</gui>
|
|
</camera-group>
|
|
</rendering>
|
|
</sim>
|
|
</PropertyList>
|