1.9. Cross-Platform Extensions

Open Inventor supplies a set of classes designed for real-time rendering of very large models. These tools can be divided into several categories:

Using multiple threads in an application can increase overall performance by making use of multiple processors, or better use of a single processor. This also enables use of multiple graphics pipes. Now, multiple graphics windows can each have their own rendering thread, multiplethreads can simultaneously traverse the same scene graph, and modification and traversal of the scene graph can safely occur in different threads. Open Inventor can also be used in immersive VR applications based on tools like CAVELib™ and Multipipe SDK™.Chapter 24, Multithreading, gives you full details on multithreading.

The SoTrackerEvent SoTrackerEvent SoTrackerEvent and SoControllerButtonEvent SoControllerButtonEvent SoControllerButtonEvent classes have been designed to be useful in immersive VR applications that use tracking. For instance, a “wand” device can generate SoTrackerEvents when moving and SoControllerButtonEvents when a button is pressed. All classes that respond to SoMouseButtonEvent SoMouseButtonEvent SoMouseButtonEvent (i.e., SoSelection SoSelection SoSelection , SoExtSelection SoExtSelection SoExtSelection , etc.) also respond to SoControllerButtonEvents. All dragger classes also respond to SoTrackerEvents and SoControllerButtonEvents. So, for example, a wand input device can be used to interact with draggers and manipulators in an immersive environment. Chapter 26, Immersive Virtual Reality discusses these events.

Open Inventor supports detection of collisions between the viewer (camera) and the scene, collisions between objects in the scene, as well as collsions between two scene graphs, one moving and one static. The following classes have been added to handle these kinds of collisions:

Chapter 23, Collision Detection explains how to use these classes.

Open Inventor supports high quality stereo projection with different types of stereo modes to render your virtual model with high realism. Software stereo is supported as well as hardware stereo (OpenGL stereo). Furthermore, a new graphical user interface dialog box, accessible from the Stereo menu item of the viewer popup menu, allows the user to interactively select the stereo mode and make adjustments to various stereo parameters.Chapter 19, Stereo Viewing , describes how to use and configure these different stereo types.

Open Inventor supports VRML 1.0, VRML 2.0 (VRML97), and X3D nodes. This is an advantage over other graphics toolkits because the VRML nodes are fully integrated, native objects in Open Inventor. This avoids the problem of translating nodes into a different representation and potentially losing information or generating inefficient VRML when writing them back out. Using Open Inventor you have complete, precise control over the nodes and their field values.Chapter 22, VRML97/ X3D Extensions explains the use of VRML 2.0 and X3D nodes.

Open Inventor provides support for programmable vertex, geometry, and fragment (pixel) shaders, allowing you to take advantage of the latest generation of graphics cards to produce more advanced real-time rendering effects.

Programming in the following languages is supported (depending, of course, on support for these shader languages by your graphics card):

The following classes provide support for programmable vertex, geometry and fragment shaders:

The basic approach is to:

  1. Write your shader code and load it into a SoVertexShader and/or SoGeometryShader and/or SoFragmentShader node. Use SoShaderParameter to set parameters (float, integer, vector, etc.) as necessary.

  2. Combine your shaders into an SoShaderProgram SoShaderProgram SoShaderProgram . They should be directly referenced by the multiple field SoShaderProgram::shaderObject.

  3. Insert this SoShaderProgram SoShaderProgram SoShaderProgram object in your scene graph above above the shapes in the scene graph that should be affected by it

Chapter 21, Shaders deals with this topic.

Remote rendering allows an Open Inventor application to both execute and render on a remote server machine. Only the optimized and compressed rendered images are sent to the local machine. This allows very large data sets to be centralized and handled on a machine with more memory, processors, and graphics hardware.

Chapter 27, Remote Rendering deals with this extension.

Starting with Open Inventor 6.1, it is also possible to do remote rendering on a cluster using ScaleViz. See Chapter 3, ScaleViz.

In addition to the actions for large model visualization and collision detection, the following new actions are available:

Open Inventor has followed the evolution of graphics boards and OpenGL in terms of texturing support. Furthermore, numerous other features have been added to provide more flexibility and improve performance. The following features have been added:

When creating your application with Open Inventor, you may need to use external dynamic libraries for specific purposes. However, the need for these libraries can depend on the use of the application. In order to save memory and loading time at start-up, you can load these dynamic libraries “on the fly” only when required.

The class SoDynamicLibManager manages the loading and the unloading of a dynamic library (cross-platform). You can query the list of all loaded libraries or whether a specific library is currently loaded. You can also inquire whether a specific library supports a particular function.

This class is used by Open Inventor to load the following libraries: Zlib, libJpeg, libTiff, libPng, libJasper, OpenAL (Windows only), FreeType, OpenFlight, and NVIDIA CG.

The library name given to the load method can include an absolute or relative path. If no path is supplied, the library will be searched for in the following paths:

OpenFlight is an industry standard real-time 3D scene description format developed and maintained by the MultiGen-Paradigm company. It was originally created in response to a need for database transportability within the visual simulation community.

A converter allows you to import OpenFlight (Version 15.7) files into the Open Inventor viewers. The OpenFlight converter extracts and converts the OpenFlight data (binary format files) to an equivalent Open Inventor scene graph.

Reading an OpenFlight file into Open Inventor is just like reading in any other kind of file. Open Inventor will open the file and automatically detects that it is an OpenFlight file. Optionally, you can tell Open Inventor explicitly that the file type is OpenFlight:

SoInput fltInput;
fltInput.openFile("myOpenFlightFile.flt");
fltInput.setCurFileType(SoInput::OpenFlight);
SoSeparator *fileContents = SoDB::readAll(&fltInput);
  
SoInput fltInput = new SoInput();
fltInput.OpenFile("myOpenFlightFile.flt");
fltInput.SetCurFileType(SoInput.FileTypes.OpenFlight);
SoSeparator fileContents = SoDB.ReadAll(fltInput);
SoInput fltInput = new SoInput();
fltInput.openFile("myOpenFlightFile.flt");
fltInput.setCurFileType(SoInput.FileTypes.OpenFlight);
SoSeparator fileContents = SoDB.readAll(fltInput);

In addition to the extension nodes mentioned previously, the following new nodes have been added by FEI: