d38fcc9979
This supports the panoramic distortion option, as found in osgViewer, in the camera file syntax of flightgear.
397 lines
12 KiB
Text
397 lines
12 KiB
Text
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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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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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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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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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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