Gabriele Cosmo
187 lines
6.5 KiB
Plaintext
187 lines
6.5 KiB
Plaintext
Extended OI Xt viewer
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=====================
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INCOMPLETE DRAFT
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G4OpenInventorXtExaminerViewer is based on and is
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a plug-in replacement for SoXtExaminerViewer which
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is a base class viewer provided by the SoXt (Coin3d)
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library. SoXtExaminerViewer is the normal viewer
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that you get when doing /vis/open OIX.
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These viewers depend on X, Xt and Xm and so are
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limited to UNIX/MAC and will not run on native
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Windows.
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The SoXtExaminerViewer is instantiated by
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G4OpenInventorXtViewer. This has been temporarily
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disabled and has been replaced by an instantiation
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of G4OpenInventorXtExaminerViewer, together with
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some additional configuration. The intention
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is to find a suitable mechanism to allow a choice
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of viewer (standard or extended) at run time.
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No modifications to user code or to any other
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Geant4 categories are required to use the extended
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viewer. Many of the implemented features are made
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possible by the SCENE GRAPH technology in Open
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Inventor which stores the scene elements and
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associated information in a structured way.
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Features
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========
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Reference Path navigation
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-------------------------
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Most of the new features are concerned with navigation
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along a "reference path" which is a piecewise
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linear path through the world. The reference path
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can be any particle trajectory, chosen as follows:
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The application can attach a "reference trajectory"
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attribute to a particular trajectory.
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If there is no such designated trajectory, the viewer
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chooses the longest trajectory as the initial reference
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path.
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Any other trajectory can be selected as the reference
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by selecting it with the mouse.
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Elements are assigned a "distance" along the reference
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path, based on the perpendicular from the element's
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placement coordinates to the path. Elements are then
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sorted by distance and the list is displayed in an
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auxiliary window of the viewer. NOTE: at present
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the path is not extrapolated at the ends, so elements
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"before" or "after" the path are assigned distances
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of 0 or the total path length respectively. This
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will be generalized in future.
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Reference path navigation controls:
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Select an element from the list: navigate along the
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path to the element's "location" (distance along
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the path.
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L,R,U,D refer to the arrow keys.
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Shift-L and Shift-R: navigate to the previous or next
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element on the path (with wraparound).
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L and R: rotate 90 degrees around the vertical axis
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U and D: rotate 90 degrees around the path
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Ctrl-L and Ctrl-R: rotate 90 degrees around the horizontal axis
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All these keys have a "repeat" function for continuous motion.
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The rotation keys put the camera in a definite orientation.
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The Shift-L and Shift-R keys can be used to "fly" along the
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path in whatever orientation is in effect.
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NOTE: if this appears to be "stuck", try switching from
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orthonormal camera to perspective camera ("cube" viewer button).
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Tools / Go to start of reference path: useful if you get lost
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Tools / Invert reference path: flips the direction of travel
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and the distance readout
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Reference path animation
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This is a special mode which flys the camera steadily along the
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path, without wraparound. Special controls are:
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Tools / Animate Ref Particle: start animation mode
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Page-Up: increase speed
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Page-Down: decrease speed
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U: raise camera
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D: lower camera
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ESC: exit animation mode
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For suitable geometries the U and D keys can be used to
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get "Star Wars" style fly-over and fly-under effects.
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Bookmarks
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At any time, the viewpoint and other camera parameters can
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be saved in a file as a labelled "bookmark".
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The view can then be restored later in the current run or
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in another run.
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The default name for the bookmark file is ".bookmarkFile"
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The first time a viewpoint is saved, this file will be
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created if it does not already exist. When the viewer
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is first opened, it will automatically read this file
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if present and load the viewpoints into the left-hand
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panel of the viewer's auxiliary window.
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Controls:
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Select viewpoint from list: restore this view
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Right-arrow VIEWER button: go to next viewpoint
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Left-arrow VIEWER button: go to next viewpoint
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"Floppy Disk" button: save current view.
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The user can type in a label for the view,
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or use the default label provided.
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File / Open Viewpoint File: loads an existing bookmark file
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File / New Viewpoint File: creates a new bookmark file for
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saving subsequent views
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Special Picking Modes
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"Console" VIEWER button: enable brief trajectory picking and
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mouse-over element readout
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For trajectories, the list of all trajectory points is
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replaced by the first and last point only, allowing easier
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identification of the particle without scrolling back.
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Passing the mouse over an element will give a readout
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of the volume name, material, and position on the
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reference path.
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"Star" VIEWER button: select new reference path
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The cursor will change to a small cross (+)
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after which a trajectory can be selected to become
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the new reference path.
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Convenience feature
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Escape from viewer without using the mouse:
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In addition to the File / Escape menu item, pressing the "e"
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key on the keyboard will exit from the viewer's X event loop.
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The viewer becomes inactive and control returns to the
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Geant4 UI prompt.
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Prototype only:
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File / Save-Load Ref Coords: status to be determined
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File / Save-Load Scene Graph: this saves the current scene graph,
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(whatever is being viewed and navigated in the viewer)
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including the geometry, camera, lighting information, into a
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file which can be read back, thus returning to a previous
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viewing "experience". This only partially works and some
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or all of the geometry may be missing. Geant4-specific
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scene elements may be lacking a "save" method.
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Known problems:
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Viewer occasionally hangs in an unknown state.
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Usually can be "cleared" by trying various viewer buttons
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or menu items. Last resort: escape to the G4 prompt and
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run more events. Viewer will usually be o.k. afterwards.
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Unpredictable mode-switching behaviour: switching between
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orthonormal and perspective camera may give wierd results.
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Navigation may appear "stuck" with orthonormal camera.
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Both the standard and extended viewers can crash the
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executable or even the X server if they are pushed
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too far (e.g. by excessive zooming).
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