Dive 3.3x Keypoints

This page contains a brief summary of the main additions from Dive 3.2 to Dive 3.3x. More detailed information can be gained through the changes log that follows with the distribution.

• Geometry Optimisers
  • Tesselator - A simple tesselator allows you to cut all pointsets into triangles. This tool should be used as a first step before producing triangle strips (see below).
  • Center Hierarchy - This tool allows you to hierarchically recenter a tree around its approximate center of gravity. Centered models will improve all operations that involve culling the scene graph, e.g. rendering, collision, intersection, etc.
  • T-stripper - A greedy algorithm allows you to convert any multi-polygon that is composed exclusively of triangles into a set of triangle strips, which are usually quicker to render.
• Texturing Improvements
  • Mip Mapping - Mip maps are now supported, this allows for visually better textures and for variable resolution depending on the distance to the viewer.
  • Texture Transformations - All views now contain a texture transformation that allows you to translate and rotate the texture mapped on their surface.
  • Native Graphics - There is now native support for the most common graphics type. In practice, Dive almost never relies on external processes to be able to read the content of textures. The supported formats are (animated) GIF, JPEG, PNG, PPM and XWD.
  • Texture Blend - Dive now supports most of the texture blending possibilities offered by OpenGL, e.g. it is possible to ignore materials when texturing.
  • Environment Mapping - Support for environment mapping is present.
• Rendering Enhancements
  • Stero - Stereo is now fully supported on Silicon Graphics machines.
  • Display Lists - There is an initial support for display lists, at the view level. This allows rendering improvements on some architectures.
  • World Background - Support for VRML-like world background is now present in the platform.
  • FOV - Different ways of associating field of view modifications to window resizes are now supported.
  • Target Frame Rate - Dive now allows to specify a target frame rate, the software far clipping plane will be adjusted dynamically to reach that goal.
  • Anti-Aliasing - Lines are now correctly anti-aliased.
• External Devices
  • HMD - Support for head mounted displays with stereo view has been addded.
  • Fastrak - Support for fastrak sensors.
  • Track-Ball - Support for a track ball through a specific plugin.
  • MSD - Support for multi-screens displays, this is currently hard coded to three different viewports and screens and has only been tested on our Onyx.
• Networking Improvements
  • Packet Size - All transiting packets have been optimised so as to reduce their size to the vital minimum.
  • Message Aggregation - Dive now allows to aggregate a series of transformations into a single message, that will lead to a single chain of network packets. Noticeable improvements in animations result from this feature.
  • DNS Helper - Dive now provides a separate DNS helper application on UNIX systems. This allow other processes to avoid blocking when resolving host names to IP addresses.
  • Weak & Strong Peers - Dive now makes a difference between weak and strong peers. Weak peers will never be able to send state transfer or to become world server, and thus take in charge some possibly heavy operations.
  • SRM Improvements - The SRM (Scalable Reliable Multicast) implementation has been consolidated, which allows the platforms to run better on wide aread networks.
  • Debug Loss Rate - Dive now has support for simulation packet loss both on reception and sending.
  • RTT - Round-Trip Time between peers is now estimated on-the-fly, which allows for better behaviour on wide area networks.
• Audio Enhancements
  • Light-Weight Groups - Dive supports multiple audio groups, their creation and manipulation is eased by a Tcl interface.
  • Sampling Rate - Dive now allows you to choose the sampling rate on sending and reception, which enables better audio quality on local networks.
  • Playout Delay - The playout delay has been minimised and can now be configured, which allows for minimised delays on local networks, but also allows to adapt to wide-area trials.
  • Separate Process - Dive offers the possibility to run audio in a separate process or preemptive thread. While this is still work in progress, the resulting audio quality is noticeably improved.
• Database Improvements
  • Identifier Comparison - Entity identifier generation and testing have been modified to allow for faster comparisons and look-ups.
  • Dynamic Rehash - The databases containing the different entities are now dynamically rehashed when the mean number of elements for each hash value gets to big. This allows for faster look-ups in the database.
  • Dynamic Reordering - The lists forming the hash tables are reordered automatically so that the last looked-up object is placed at the head of the list automatically. This minimises the number of iterations the next time it is looked up, a situation that occurs quite often.
  • General Collections - Dive now supports the concept of collection. Collections are sets of entities, gathered in no specific order and across the hierarchy. Each entity has a floating membership value and collections can contain collections.
  • Access Control - There is support for some access control and possibility exists to control the actions that can be performed by a user or collection of users.
• Additional 3D File Formats
  • 3DS - There is an initial support for 3D Studio files, the code is based on the file format "specifications" that are found at various locations .
  • VRML97 - Initial support for the VRML97 specification, some primitives are not yet supported and only some of the animation nodes are supported through Dive/Tcl scripts.
  • AC3D - Internal support for the AC3D file format. Note that loading AC3D files directly into Dive gives generally better results than exporting Dive files from AC3D.
  • Binary Files - Dive now supports a binary file format, note that binary files created with 3.3x are likely not to work with further versions. Consequently, binary files should only be used to speed up file loading and the original text files should always kept as a backup.
• User Interface
  • Awareness List - The actor list has been improved and offers a quick view of what other users present in the same world are doing and allows for some common actions from a right-click menu. The list can be used as an awareness mechanism by running continuously and hiding the rendering window.
  • Shell Prompt - "diva" can now be started without any graphical interface, but with a Dive/Tcl prompt that allows you to enter commands and gather information about the environment programatically.
  • Better Widgets - The interface has been improved through the use of mega-widgets, especially the configure table edition and the scripting consoles.
  • Menu Reorganisation - The menus have been reorganised slightly and some accelerators have been added.
  • Object-Based Navigation - "diva" can now be started as an object viewer. The specific navigation methods can also be used from "vishnu", through a special vehicle.
  • Built-In Tools - An interactive box editor now allows the user to rescale any object dynamically. Similarily, a distance measurement tool can be accessed from the interface.
• Programming Interface
  • Plugin - Any Dive application can now load a list of plugins when starting up. These plugins will be activated through the call of a specific init function and they have access to all of the C programming facilities of the platform.
  • Dive/Tcl - As for every new release, some new Dive/Tcl commands have been added.
• Miscellaneous
  • Internal Operations - Dive now integrates an internal CPP (C pre-processor, used for resolving macros in .vr files) and an internal unzipping facility.
  • Logging - The logging facilities have been improved, especially through the a separate process that logs all actor movements.
  • Persistency - A first step towards persistent worlds has been taken. This is currently achieved through running one or several processes which only goal is to store the state of the environments.
  • SQL Support - SQL support has been added through a plugin.

Emmanuel Frécon - emmanuel@sics.se
Olov Ståhl - olovs@sics.se