Coin3D-Qt.zip_Coin3D_Molongcoin-qt代理_qt-coin3d

Coin3D and Qt:

1

The Solution for Cross-platform 3D Application Development

KONGSBERG SIM

1 Introduction

Coin3D and Qt together present the easiest way to create powerful, cross-platform 3D applications. Kongsberg

SIM’s Coin3D is an OpenGL based, retained mode 3D graphics rendering library that is fully compatible with SGI’s

Open Inventor. Qt is a high-performance, cross-platform application development framework that makes developing

can be updated to use Coin. SoQt’s interface closely matches SGI’s original SoXt GUI bindings, making it easier to port

legacy X Windows Inventor applications to Qt.

2 First Steps with SoQt

Before delving into the details of SoQt and Coin, it is useful to see SoQt in action to illustrate just how simple it can be

to develop a 3D Qt application. The goal is to load an Open Inventor le containing a scene, display it, and provide user

interaction.

int main( int argc, char** argv ) {

// Initializes SoQt library (and implicitly also the Coin and Qt

// libraries). Returns a top-level / shell Qt window to use.

QWidget * mainwin = SoQt::init(argc, argv, argv[0]);

SoQtExaminerViewer * eviewer = new SoQtExaminerViewer(mainwin);

eviewer->setSceneGraph(root);

eviewer->show();

// Pop up the main window.

SoQt::show(mainwin);

// Loop until exit.

SoQt::mainLoop();

// Clean up resources.

delete eviewer;

root->unref();

Coin3D and Qt:

KONGSBERG SIM

drawing, interaction via the mouse, and has several buttons and thumbwheels to control the display. Of course SoQt allows

the use of the complete Qt API to create far more sophisticated user interfaces. This example just demonstrates how easy

it can be load, display, and manipulate a scenegraph in a Qt application using Coin and SoQt.

Examining the code in more detail provides some insight into how SoQt and Coin work. The rst key piece of code from

the example above is:

QWidget * mainwin = SoQt::init(argc, argv, argv[0]);

This initializes the SoQt and Qt libraries, and returns a pointer to a QWidget that will act as a container for the viewer once

it is created. The next several lines open an Inventor scene le and load the data into a scene graph..

SoInput sceneInput;

if ( !sceneInput.openFile( “stagedancers.iv” ) )

Figure 1

Coin3D and Qt:

3

The Solution for Cross-platform 3D Application Development

KONGSBERG SIM

This example uses the high-level SoQtExaminerViewer class to provide a complete viewer with all the features described

above. SoQt offers several classes capable of displaying a scenegraph, each with different levels of features and exibility.

These will be described in detail later. Next we give the viewer the scenegraph to display and then show it:

eviewer->setSceneGraph(root);

context in QWidget and draw onto that widget using OpenGL; however, it does not provide an easy way to integrate with

more complex rendering libraries like Coin. SoQt is the glue between Qt and Coin, allowing the application programmer to

use the power of Coin for 3D rendering and the simplicity of Qt for the user interface. Both Coin and Qt isolate the developer

from the underlying platform dependencies and are completely cross-platform.

SoQt builds on Qt’s QGL library. Qt interacts with the underlying windowing system to create OpenGL contexts, create

and manage windows, and handle windows system events. SoQt uses the OpenGL widgets created by Qt, but adds an

interface for rendering Coin scenegraphs instead of pure OpenGL. SoQt provides automatic event handling: just as Qt

translates low-level window system events into higher-level QEvents, SoQt translates these QEvents into Coin SoEvents.

SoEvents describe how to manipulate the camera or other objects in the scenegraph. Event types handled by SoQt include

mouse events, keyboard events, and window resizing events.

several available classes, each offering differing levels of abstraction and customization. Some can be used directly while

others are abstract and must rst be subclassed.

Figure 2 shows the inheritance hierarchy of the viewing classes. The bottommost classes, the SoQtFullViewer and its

subclasses, provide the easiest way to display a scenegraph. They are fully functional viewers, complete with working

user interface components. They are mainly useful for rapid development and prototyping because their user interface

components typically will not match an application’s desired look-and feel. The SoQtViewer offers much of the functionality

of these full viewers, but without the UI widgets. It has many convenience functions for easily setting up, displaying, and

manipulating scenegraphs. The SoQtRenderArea and SoQtGLWidget classes are the most general of the classes for

displaying scengraphs. They offer greater exibility at the cost of more work. This section will examine the details of these