A primer to the vishnu tk interface

Vishnu is a browser that gives access to multi-user 3D Dive and VRML worlds. The browser is designed to be easy to use. Further information is available on a world-wide web page at http://www.sics.se/dive, or by the Dive contacts (mail: dive-help@sics.se). You can also follow the tutorial.

1. The vishnu window interface

The vishnu window consists of three parts: a header, a viewport and a statusbar. The header consists of a set of menubuttons with pull-down menus and a possible button bar with shortcuts to some usual operations. The viewport displays a 3D view as seen from the user. The status bar located at the bottom of the window displays "interesting" information, such as the current world name.

You can "tear off" menus by pressing the dotted line at the top of each pull-down menu.

1.1 Fundamental concepts - Glossary

Actor - The virtual user, vishnu is bound to one actor.
World - A space containing objects where actors reside.
Object - Entities with graphical representations.
Avatar - The virtual representation of an actor consisting of a set of objects.
Head - Top part of avatar that can be independently rotated.
Eye - The object of the avatar from where the current scene is rendered.
Navigate - The act of moving the actor's avatar in the world.
Marked object - The actor's currently selected object (with shift-select or double-click).
Graspable - Only graspable objects may be marked or moved.

2. Mouse interaction

Vishnu interaction is based on mouse interaction and to some extent keyboard interaction. The four main operations are "activate", "mark", "move" and "rotate". In vishnu, objects are "activated" by pressing the left mouse button. Objects are "marked" by pressing the left mouse button while pressing the shift button or double-clicking with the left mouse button. "Move" is performed by the middle mouse button, while "rotate" by the right mouse button.

2.1 Left mouse button: "activate" and "mark"

When the left mouse button is pressed, objects are "activated". One example of an activated object is a vehicle icon which moves a user when it is activated.

If the shift button is pressed at the same time as the left mouse button, objects are "marked". When an object is marked, it is "blinked". Several operations may be performed on marked objects, such deletion, movements, etc. (see the Objects menu). Only graspable objects may be marked. Marking actually selects an object hierarchy, and it is possible to "traverse" the hierarchy and thereby access sub-hierarchies and individual objects.

2.2 Middle mouse button : "move"

By pressing the middle mouse button and dragging, graspable objects are moved around. If the shift button is pressed at the same time, (without moving) the object is attached to the user. The object then moves along with the user.

If the control button is simultaneously pressed, the object is moved in the z-axis of the user (in/out of the screen)

2.3 Right mouse button : "rotate"

If an object is selected while pressing the right mouse button, the object may be rotated by moving the mouse while keeping the mouse button pressed.

If the control button is simultaneously pressed, the object is rotated according to a different mode.

3. File menu

• Open URL: Open an URL and spawn a viewer for it, according to its Mime type. If it is a VRML or DIVE file, it will be interpreted as a loadable object and inserted in the current world. Other MIME types such as HTML or pictures will be shown in desktop windows.
• Configure: The system may be reconfigured during runtime - an alteranitve is to change the .dive_configure file and restart. Currently defined configuration includes:
• Proxy Server - Define a proxyserver for a non-multicast client to which it directs its output and receives its input.
• Name Server - Define a nameserver.
• Http Proxyr - Direct all http request to a HTTP proxy server.
• Bird Server - Define a birdserver.
• Tk Interface - Tk interface configuration.
• Talk - Tk talk interface configuration.
• Configure file - All default settings in the configure file are shown in a window. The default settings can be changed and saved. Saving is not recommended since all defaults settings will be copied to your local configuration file.
• Audio: Enable spatialized ambient and conference audio communication between participants. The Audio menu first contains checkbuttons:
• Audio in : Select audio in to be on or off.
• Audio out : Select audio out to be on or off.
• Then a spatialization of the 3D audio can be chosen:
• Mono spatialization
• Headphone spatialization
• Four channel spatialization
• Headphone: no attenuation
• Configure Audio will open a dialog box to refine the audio configuration parameters.
• Video: Enable video communication between participating peers. The video menu first contains checkbuttons:
• Video in : Select video in to be on or off.
• Video out : Select video out to be on or off.
• Then an image quality:
• Nicest
• Nearest
• Fastest
• Configure Video will open a dialog box to refine the video configuration parameters.
• Screendump: Dump a rendering image (a snapshot) to file.
• Record Movie: Record a rendering movie and save it as a sequence of image files. This operation consumes a fair amount of disk space!
• Empty Tcl Cache: Empty the cache for tcl script.
• Notification History: Open a window with an history of all the notifications that were shown in the status bar since the beginning of the session.
• Exit: Exit vishnu. You can also type ESC in the vishnu viewport.

4. Render menu

The Render Menu contains operations to control the current setting of the 3D graphic rendering. The stationary flags sets the rendering when the actor is not moving, while the Motion flags sets the rendering when the actor moves.

• Render Off: If set, nothing is rendered.
• Stationary rendering flags:
• filled polys: if set, polygons are rendered with filled surfaces, otherwise as wireframes.
• texture: if set, textures are rendered.
• smooth shading: If set, polygons and objects that are marked for smoothing will be smooth shaded using Gouraud shading.
• transparency: If set, polygons and objects that are marked transparent will be rendered in the correct order.
• lod: if set, all level-of-details (lods) are rendered. If not, only the simplest lod is shown.
• Motion rendering flags:
• wireframe: if set, polygons are rendered as wireframes when moving.
• no texture: if set, textures are not rendered when moving.
• flat shading: If set, all polygons and object are rendered with flat shading.
• simplest lod: if set, only the simplest lod is shown when moving.

5. World menu

The World menu contains operations on the world that the actor associated with vishnu (self) is in.

• Load: Open new world by giving a universal resource locator (URL) or local file name. The actor leaves the current world and is transferred into the new.
• Save: Save complete world to local file.
• Export: Export the complete current world to another file format. Currently, VRML 1.0 and AC3D file formats are supported.
• World->AC3D: Send the content of the current to a running AC3D, in which edition will be possible. Communication between Dive and AC3D is only possible on secure hosts.
• Info: Presents name and information of current world.
• Resident: If set, world is always left resident in memory even when the actor leaves it. In practice, this means that the world will continue living even if not currently rendered. It is then possible to come back to a resident world to see how it has evolved.
• Reconnect: Disconnect and reconnect from current world. If the user is alone in the world, the world will be reread from file.

6. Object menu

In the objects menu, operations with objects can be performed. Apart from loading and saving objects, operations can be performed on "marked" objects (with "shift select").

• Load in Front: Load an object by giving an URL or file name. The loaded object is inserted into the current world "in front of" the actor.
• Load in Place: Load an object by giving an URL or file name. The loaded object is inserted into the current world at the position defined in the file (or URL).
• Save: Save the marked object to local file.
• Export: Export the marked object to another file format. Currently, VRML 1.0 and AC3D file formats are supported.
• User Subjective View: Modify local subjective view of the marked object.
• Group Subjective View: Modify group subjective view of the marked object. All users which have declared being member of the same group will share the same subjective view. This option requires to run the subjective login before.
• Info: Display information on marked object.
• Source: Display source on marked object.
• Edit: Display source on marked object. The source can sometimes be modified and saved or replaced with the original object. Note however that the use of all constants declared in dive.vh is impossible.
• Material Edit: Start an interactive material editor on the marked object.
• Dive/Tcl Editor: Start an interactive Dive/Tcl editor bound to the selected object. Callbacks and timers can be registered "on the fly". See the Dive/Tcl behaviour document: http://www.sics.se/dive/manual/tcl.html.
• Dive/Tcl Shell: Start a simple Dive/Tcl shell.
• Marked->AC3D: Send the current marked object for edition to a running AC3D. Communication between Dive and AC3D is only possible on secure hosts.
• AC3D->marked: Replace the current marked object by the object which has been edited in AC3D. Communication between Dive and AC3D is only possible on secure hosts.
• Delete: Remove marked object.
• Prune: Remove the marked object from its hierarchy and add it as a top-object to the world. Only applies to sub-objects.
• Add sub: Add a sub object to the marked object. The sub object is selected interactively after the command is chosen. It is illegal to add subs of the same hierarchy.
• Align: Align marked object to the y-axis of the coordinate system of the world, or the super object, if the marked object is a sub.
• Mark down: Mark object below the currently marked object. That is, traverse the object hierarchy by marking the next object "closer" to the view that was interacted with by "shift-select".
• Mark up: Mark the object above the currently marked object. That is traverse upwards towards the root in an object hierarchy.
• Graspable: Make the marked object graspable. As such, it can be moved and rotated by grasping it with the mouse buttons, while still being part of a hierarchy. To make it truly independent, make "Remove sub".
• Ungraspable: Make the marked object ungraspable.
• Blink: Blink marked object. Blinking is done by turning wireframe on.
• Smooth: Try to smooth the polygons of the currently marked object and all its subs, i.e. calculate automatically normals in order to improve Gouraud shading.
• Center Hierarchy: Will center the marked object and all its subs around their approximative center of gravity. This operation will improve rendering performance on badly modelled objects.
• Recorder: A recorder (alpha-version). Record movements of any object or an actor's avatar.
• Bring: Move the marked object to the actor.

7. Self menu

Operations performed on the actor associated with this vishnu.

• Load: Load new actor avatar from URL or local file. Old avatar will be left behind.
• Save: Save actor avatar to local file.
• Info: Display information on actor avatar.
• Dive/Tcl Shell: Start an interactive Dive/Tcl shell. From this prompt Div/Tcl commands can be interactively entered to the actor associated with vishnu. See the Dive/Tcl behaviour document: http://www.sics.se/dive/manual/tcl.html.
• Dive/Tcl Shell: Start a simple Dive/Tcl shell.
• Right eye: Change viewport to the actor's right eye.
• Left eye: Change viewport to the actor's left eye.
• Polar view: Change viewport to a position above the actor's avatar (the positive y-axis).
• Side view: Change viewport to a side position of the actor's avatar.
• Rear view: Change viewport to a position behind the actor's avatar.
• Align: Align the coordinate axes of the actor's avatar to the world's global system. If you are lost in cyberspace, this will make your avatar "stand up", i.e., the avatar's y-axis is parallel to the world's y-axis. Same effect if "home" key is pressed.
• Align head to avatar: Rotate head so that it faces straight ahead with respect to the avatar.
• Align avatar to head: Rotate avatar so that it faces the same way as the head. Useful if you have turned your head in an "interesting" position and you wish to continue moving your avatar in this direction.
• Align as marked object: Rotate avatar so that it faces the same way as the currently marked object.
• Attach to marked: Attach the actor's avatar as a sub-object to the marked object. If the marked object moves, the avatar moves along with it.
• Detach: Detach the avatar from super object, if any. Usually meaningful only if Attach to marked has been called.
• Change avatar: Replace the current avatar with the marked object. The old avatar will be left behind.
• Undo change avatar: Undo the most recent avatar change.
• Subjective login: Declare which user and group name for the subjective views module.

8. Navigate menu

Vehicles represent tools that allow a user to navigate in 3D space.

• Keyboard: Enable the keyboard vehicle (see below).
• Mouse: Enable the mouse vehicle. The mouse vehicle icon has three sub-icons, the upper triangle moves the avatar forward and rotates sideways, the middle box-icon translates the avatar up and sideways, while the lower icon pitch/rolls the avatar.
• Fly: Enable the Fly vehicle. When interacting with the Fly vehicle's triangle-icon, the avatar behaves as an aeroplane; while moving the forward, mouse movement controls pitch/roll.
• Simple: Enable the simple vehicle, a simple 2D vehicle where you can move forward and sideways in a 2D plane.
• Head: A Tk tool that enables independent head motion.
• Walk: A Tk tool for simple "walk-style" motion.
• Translation: A Tk tool for simple translation motion (forward, backward, left and right).
• To start: Move actor's avatar to world's start position.
• To origo: Move actor's avatar to world origo.
• To marked: Move actor's avatar to marked object.
• Increase speed: Increase default vehicle speed. PgUp can also be used.
• Decrease speed: Decrease default vehicle speed. PgDn can also be used.
• Use Velocity: If set, all non-Tk vehicles will use velocity to move the avatar. Using velocity will result in a smoother rendering and less network traffic.

Keyboard vehicle

Navigate using the keyboard vehicle:

Turn left.
Turn right.
Move forward.
Move backward.
Home Align y-axis to world.
+/- Zoom in or out.
PgUp/PgDown Increase/Decrease speed.
F1,...,F6 Rotate and change eye view.

• Pressing Shift while moving increases the speed.
• Control and Alt controls movement in other degrees of freedom.

9. Tools menu

• Viewpoints: Display a list of all viewpoints (cameras) in the current world. Select "GoTo" or double click on a viewpoint to go to the viewpoint.
• Bookmarks: Display a list of all bookmarks you have already defined. Buttons are provided to add a new bookmark (i.e. remember the current URL and the current position and orientation), to delete the selected bookmarks or to go to a specific bookmark. Bookmarks are saved at the end of each dive session in a file called .dive_bookmarks in your HOME directory.
• Worlds: Presents an (automatically) updated list of all the worlds which have been visited since the beginning of a session. A double click on a world name or a click in the "Go To" button will teleport to the selected world.
• Actors: Display a list of all actors present in world. An actor can be selected in the list, and operations including sending messages and going to the selected actor are available.
• Inspect by Name: Find an entity in the database and display an inspector with as much as possible information for the entity.
• Send Message to all: Send messages to all the other participants of this world.
• Send Message to Actor: Send messages to actor associated with marked object. Also accessible from Actors tools menu.

10. Window menu

The window menu has an entry for each of the top level window which are currently opened by the Dive viewer. Clicking on an entry will deiconify the window, if necessary and raise it to the front.

11. Help menu

• About: "about message"
• On Vishnu: This text.
• On Dive: Some information about Dive - the distributed multiuser virtual environment system.
• On multiple users: Information about how to run multiple users.
• On audio: Information about audio.
• Release Notes: Information on the release.
• Tutorial: A tutorial for novel users of Dive and also an introduction to the system.

12. Status bar

The status bar shows notifications from Dive, such as the number of bytes which have been read since an URL was opened, the HTTP connection status, the result of an HTTP connection, etc.

When the button bar is not shown, the status bar shows additionally the name of the current world, and the URL that was used to access it. The position and presence of the button bar can be controlled using its positioning button or the Tk interface configuration.

13. Button bar

The Button bar shows shortcuts to useful operations which may, otherwise, be found in the menus. The button to the extreme left will attach/detach the button bar from vishnu main window. The Dive logo will be rotating each time Dive is reading from a URL or a local file. Clicking on it will open a menu which replicates the menu of the main window. The location entry shows the URL of the current world and is editable. Pressing return once edition is done will connect to another world.

The remaining buttons, from left to right, in the button bar have the following functions:

• Load: Open new world by giving a universal resource locator (URL) or local file name. The actor leaves the current world and is transferred into the new.
• Reconnect: Disconnect and reconnect from current world. If the user is alone in the world, the world will be reread from file.
• Load in Front: Load an object by giving an URL or file name. The loaded object is inserted into the current world "in front of" the actor.
• Load in Place: Load an object by giving an URL or file name. The loaded object is inserted into the current world at the position defined in the file (or URL).
• Delete: Remove marked object.
• Info: Display information on marked object.
• Mark down: Mark object below the currently marked object. That is, traverse the object hierarchy by marking the next object "closer" to the view that was interacted with by "shift-select".
• Mark up: Mark the object above the currently marked object. That is traverse upwards towards the root in an object hierarchy.
• Align: Align marked object to the y-axis of the coordinate system of the world, or the super object, if the marked object is a sub.
• Graspable: Make the marked object graspable. As such, it can be moved and rotated by grasping it with the mouse buttons, while still being part of a hierarchy. To make it truly independent, make "Remove sub".
• Ungraspable: Make the marked object ungraspable.