OpenSceneGraph实现的NeHe OpenGL教程 - 第八课

• 简介

本课是在第七课的基础上实现将立方体变透明的效果，其中用到了OpenGL中的混合(Blend)

• 实现

在OpenGL中如何实现混合以及混合实现的原理和过程在NeHe教程中已经解释的很清楚了，在这里就不在赘述，本课主要探讨在OSG中实现混合的效果，混合同样是作为一种StateSet的方式来进行处理的，OSG中的混合主要涉及到一下几个类BlendFunc、BlendEquation和BlendColor，对应于OpenGL中的glBlendFunc 、glBlendEquation和glBlendColor三个函数，对混合的参数进行一些设置。本课中我们参考NeHe教程中设置混合的计算方式定义如下的BlendFunc

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1. osg::BlendFunc *blendFunc = new osg::BlendFunc(GL_SRC_ALPHA, GL_ONE, 0.5, 0.5);  
2. quadGeometry->getOrCreateStateSet()->setAttribute(blendFunc,  
3.     osg::StateAttribute::ON);  

需要注意的是我们需要将初始的清除背景的颜色的alpha值设置为0.5

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1. camera->setClearColor( osg::Vec4(0.0, 0.0, 0.0, 0.5) );  

在按下键盘上B键的时候开启和关闭混合模式

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1. if (ea.getKey()== osgGA::GUIEventAdapter::KEY_B)  
2. {  
3.     static int i = 0;  
4.     if (i % 2 == 0) {  
5.         root->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::ON);  
6.     } else {  
7.         root->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::OFF);  
8.     }  
9.     ++i;  
10. }  

其他的代码与第七课相同，编译运行程序后点击B键时可以看到透明的效果。

附：本课源码(源码中可能存在错误和不足，仅供参考)

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1. #include "../osgNeHe.h"  
2.   
3. #include <QtCore/QTimer>  
4. #include <QtGui/QApplication>  
5. #include <QtGui/QVBoxLayout>  
6.   
7. #include <osgViewer/Viewer>  
8. #include <osgDB/ReadFile>  
9. #include <osgQt/GraphicsWindowQt>  
10.   
11. #include <osg/MatrixTransform>  
12. #include <osg/NodeVisitor>  
13. #include <osg/Texture2D>  
14.   
15. #include <osgGA/GUIEventAdapter>  
16.   
17. #include <osg/Light>  
18. #include <osg/LightModel>  
19. #include <osg/LightSource>  
20.   
21. #include <osg/BlendFunc>  
22.   
23. float textureVertices[][2] = {  
24.     //Front Face  
25.     {0.0f, 0.0f},  
26.     {1.0f, 0.0f},  
27.     {1.0f, 1.0f},  
28.     {0.0f, 1.0f},  
29.     // Back Face  
30.     {1.0f, 0.0f},  
31.     {1.0f, 1.0f},  
32.     {0.0f, 1.0f},  
33.     {0.0f, 0.0f},  
34.     // Top Face  
35.     {0.0f, 1.0f},  
36.     {0.0f, 0.0f},  
37.     {1.0f, 0.0f},  
38.     {1.0f, 1.0f},  
39.     // Bottom Face  
40.     {1.0f, 1.0f},  
41.     {0.0f, 1.0f},  
42.     {0.0f, 0.0f},  
43.     {1.0f, 0.0f},  
44.     // Right face  
45.     {1.0f, 0.0f},  
46.     {1.0f, 1.0f},  
47.     {0.0f, 1.0f},  
48.     {0.0f, 0.0f},  
49.     // Left Face  
50.     {0.0f, 0.0f},  
51.     {1.0f, 0.0f},  
52.     {1.0f, 1.0f},  
53.     {0.0f, 1.0f}  
54. };  
55.   
56. float QuadVertices[][3] = {  
57.   
58.     {-1.0f, -1.0f,  1.0f},  
59.     { 1.0f, -1.0f,  1.0f},  
60.     { 1.0f,  1.0f,  1.0f},  
61.     {-1.0f,  1.0f,  1.0f},  
62.   
63.     {-1.0f, -1.0f, -1.0f},  
64.     {-1.0f,  1.0f, -1.0f},  
65.     { 1.0f,  1.0f, -1.0f},  
66.     { 1.0f, -1.0f, -1.0f},  
67.   
68.     {-1.0f,  1.0f, -1.0f},  
69.     {-1.0f,  1.0f,  1.0f},  
70.     { 1.0f,  1.0f,  1.0f},  
71.     { 1.0f,  1.0f, -1.0f},  
72.   
73.     {-1.0f, -1.0f, -1.0f},  
74.     { 1.0f, -1.0f, -1.0f},  
75.     { 1.0f, -1.0f,  1.0f},  
76.     {-1.0f, -1.0f,  1.0f},  
77.   
78.     { 1.0f, -1.0f, -1.0f},  
79.     { 1.0f,  1.0f, -1.0f},  
80.     { 1.0f,  1.0f,  1.0f},  
81.     { 1.0f, -1.0f,  1.0f},  
82.   
83.     {-1.0f, -1.0f, -1.0f},  
84.     {-1.0f, -1.0f,  1.0f},  
85.     {-1.0f,  1.0f,  1.0f},  
86.     {-1.0f,  1.0f, -1.0f}  
87.   
88. };  
89.   
90. float normalVertics[][3] = {  
91.     // Front Face  
92.     { 0.0f, 0.0f, 1.0f},  
93.     // Back Face  
94.     { 0.0f, 0.0f,-1.0f},  
95.     // Top Face  
96.     { 0.0f, 1.0f, 0.0f},  
97.     // Bottom Face  
98.     { 0.0f,-1.0f, 0.0f},  
99.     // Right face  
100.     { 1.0f, 0.0f, 0.0f},  
101.     // Left Face  
102.     {-1.0f, 0.0f, 0.0f}  
103. };  
104.   
105. //////////////////////////////////////////////////////////////////////////  
106. //FindFirstNamedNodeVisitor用来遍历寻找与指定名称相同的节点  
107.   
108. class FindFirstNamedNodeVisitor : public osg::NodeVisitor  
109. {  
110. public:  
111.     FindFirstNamedNodeVisitor(const std::string& name):  
112.       osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ALL_CHILDREN),  
113.           _name(name), _foundNode(NULL) {}  
114.   
115.       virtual void apply(osg::Node& node)  
116.       {  
117.           if (node.getName()==_name)  
118.           {  
119.               _foundNode = &node;  
120.               return;  
121.           }  
122.           traverse(node);  
123.       }  
124.   
125.       std::string _name;  
126.       osg::Node *_foundNode;  
127. };  
128.   
129. //////////////////////////////////////////////////////////////////////////  
130. //RotateCallback  
131.   
132. class RotateCallback : public osg::NodeCallback  
133. {  
134.   
135. public:  
136.     RotateCallback(osg::Vec3d rotateAxis, double rotateSpeed) :   
137.       osg::NodeCallback(),  
138.           _rotateAxis(rotateAxis),   
139.           _rotateSpeed(rotateSpeed),  
140.           _rotateAngle(0.0)  
141.       {  
142.           //Nop  
143.       }  
144.   
145.       void setRotateSpeed(double speed)  
146.       {  
147.           _rotateSpeed = speed;  
148.       }  
149.   
150.       double getRotateSpeed() const  
151.       {  
152.           return _rotateSpeed;  
153.       }  
154.   
155.       virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)  
156.       {  
157.           osg::MatrixTransform *currentMT = dynamic_cast<osg::MatrixTransform*>(node);  
158.           if (currentMT)  
159.           {  
160.               //获取当前的平移位置  
161.               osg::Vec3d currentTranslate = currentMT->getMatrix().getTrans();  
162.               osg::Matrix newMatrix = osg::Matrix::rotate(_rotateAngle, _rotateAxis) * osg::Matrix::translate(currentTranslate);  
163.               currentMT->setMatrix(newMatrix);  
164.               _rotateAngle += _rotateSpeed;  
165.           }  
166.   
167.           traverse(node, nv);  
168.       }  
169.   
170.   
171. private:  
172.     osg::Vec3d _rotateAxis;         //旋转轴  
173.     double        _rotateSpeed;     //旋转速度  
174.     double        _rotateAngle;     //当前旋转的角度  
175. };  
176.   
177.   
178.   
179.   
180. //////////////////////////////////////////////////////////////////////////  
181.   
182. class ManipulatorSceneHandler : public osgGA::GUIEventHandler  
183. {  
184. public:  
185.     ManipulatorSceneHandler()  
186.     {  
187.     }  
188.   
189.     virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)  
190.     {  
191.         osgViewer::Viewer *viewer = dynamic_cast<osgViewer::Viewer*>(&aa);  
192.         if (!viewer)  
193.             return false;  
194.         if (!viewer->getSceneData())  
195.             return false;  
196.         if (ea.getHandled())   
197.             return false;  
198.   
199.         osg::Group *root = viewer->getSceneData()->asGroup();  
200.   
201.         switch(ea.getEventType())  
202.         {  
203.         case(osgGA::GUIEventAdapter::KEYDOWN):  
204.             {  
205.                 if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Left)  
206.                 {  
207.                     FindFirstNamedNodeVisitor fnv("yRotMT");  
208.                     root->accept(fnv);  
209.   
210.                     osg::Node *mtNode = fnv._foundNode;  
211.                     osg::MatrixTransform *yRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode);  
212.                     if (!yRotMT)  
213.                         return false;  
214.   
215.                     RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(yRotMT->getUpdateCallback());  
216.   
217.                     if (!rotCallback)  
218.                         return false;  
219.   
220.                     double speed = rotCallback->getRotateSpeed();  
221.                     speed += 0.02;  
222.                     rotCallback->setRotateSpeed(speed);  
223.   
224.                 }  
225.   
226.                 if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Right)  
227.                 {  
228.                     FindFirstNamedNodeVisitor fnv("yRotMT");  
229.                     root->accept(fnv);  
230.   
231.                     osg::Node *mtNode = fnv._foundNode;  
232.                     osg::MatrixTransform *yRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode);  
233.                     if (!yRotMT)  
234.                         return false;  
235.   
236.                     RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(yRotMT->getUpdateCallback());  
237.   
238.                     if (!rotCallback)  
239.                         return false;  
240.   
241.                     double speed = rotCallback->getRotateSpeed();  
242.                     speed -= 0.02;  
243.                     rotCallback->setRotateSpeed(speed);  
244.                 }  
245.   
246.                 if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Up)  
247.                 {  
248.                     FindFirstNamedNodeVisitor fnv("xRotMT");  
249.                     root->accept(fnv);  
250.   
251.                     osg::Node *mtNode = fnv._foundNode;  
252.                     osg::MatrixTransform *xRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode);  
253.                     if (!xRotMT)  
254.                         return false;  
255.   
256.                     RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(xRotMT->getUpdateCallback());  
257.   
258.                     if (!rotCallback)  
259.                         return false;  
260.   
261.                     double speed = rotCallback->getRotateSpeed();  
262.                     speed += 0.02;  
263.                     rotCallback->setRotateSpeed(speed);  
264.                 }  
265.   
266.                 if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Down)  
267.                 {  
268.                     FindFirstNamedNodeVisitor fnv("xRotMT");  
269.                     root->accept(fnv);  
270.   
271.                     osg::Node *mtNode = fnv._foundNode;  
272.                     osg::MatrixTransform *xRotMT = dynamic_cast<osg::MatrixTransform*>(mtNode);  
273.                     if (!xRotMT)  
274.                         return false;  
275.   
276.                     RotateCallback *rotCallback = dynamic_cast<RotateCallback*>(xRotMT->getUpdateCallback());  
277.   
278.                     if (!rotCallback)  
279.                         return false;  
280.   
281.                     double speed = rotCallback->getRotateSpeed();  
282.                     speed -= 0.02;  
283.                     rotCallback->setRotateSpeed(speed);  
284.                 }  
285.   
286.                 if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Page_Up)  
287.                 {     
288.                     FindFirstNamedNodeVisitor fnv("zoomMT");  
289.                     root->accept(fnv);  
290.   
291.                     osg::Node *mtNode = fnv._foundNode;  
292.                     osg::MatrixTransform *zoomMT = dynamic_cast<osg::MatrixTransform*>(mtNode);  
293.                     if (!zoomMT)  
294.                         return false;  
295.   
296.                     osg::Vec3 trans = zoomMT->getMatrix().getTrans();  
297.                     trans.set(trans.x(), trans.y(), trans.z() + 0.2);  
298.                     zoomMT->setMatrix(osg::Matrix::translate(trans));  
299.                 }  
300.   
301.                 if (ea.getKey()== osgGA::GUIEventAdapter::KEY_Page_Down)  
302.                 {  
303.                     FindFirstNamedNodeVisitor fnv("zoomMT");  
304.                     root->accept(fnv);  
305.   
306.                     osg::Node *mtNode = fnv._foundNode;  
307.                     osg::MatrixTransform *zoomMT = dynamic_cast<osg::MatrixTransform*>(mtNode);  
308.                     if (!zoomMT)  
309.                         return false;  
310.   
311.                     osg::Vec3 trans = zoomMT->getMatrix().getTrans();  
312.                     trans.set(trans.x(), trans.y(), trans.z() - 0.2);  
313.                     zoomMT->setMatrix(osg::Matrix::translate(trans));  
314.                 }  
315.   
316.                 if (ea.getKey()== osgGA::GUIEventAdapter::KEY_L)  
317.                 {  
318.                     static int i = 0;  
319.                     if (i % 2 == 0) {  
320.                         root->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::ON);  
321.                     } else {  
322.                         root->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);  
323.                     }  
324.                     ++i;  
325.                 }  
326.   
327.                 if (ea.getKey()== osgGA::GUIEventAdapter::KEY_B)  
328.                 {  
329.                     static int i = 0;  
330.                     if (i % 2 == 0) {  
331.                         root->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::ON);  
332.                     } else {  
333.                         root->getOrCreateStateSet()->setMode(GL_BLEND, osg::StateAttribute::OFF);  
334.                     }  
335.                     ++i;  
336.                 }  
337.   
338.                 if (ea.getKey()== osgGA::GUIEventAdapter::KEY_F)  
339.                 {  
340.                     FindFirstNamedNodeVisitor fnv("quadGeode");  
341.                     root->accept(fnv);  
342.   
343.                     osg::Node *mtNode = fnv._foundNode;  
344.                     osg::Geode *quadGeode = dynamic_cast<osg::Geode*>(mtNode);  
345.                     if (!quadGeode)  
346.                         return false;  
347.   
348.                     osg::Texture2D *texture2D = dynamic_cast<osg::Texture2D*>(quadGeode->getOrCreateStateSet()->getTextureAttribute(0, osg::StateAttribute::TEXTURE));  
349.   
350.                     static int i = 0;  
351.                     if (i % 3 == 0) {  
352.                         texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);  
353.                         texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);  
354.                     } else if (i % 3 == 1) {  
355.                         texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);  
356.                         texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR_MIPMAP_NEAREST);  
357.                     } else {  
358.                         texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::NEAREST);  
359.                         texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::NEAREST);  
360.                     }  
361.                     ++i;  
362.                 }  
363.             }  
364.         default: break;  
365.         }  
366.         return false;  
367.     }  
368. };  
369.   
370. //////////////////////////////////////////////////////////////////////////  
371.   
372.   
373.   
374. class ViewerWidget : public QWidget, public osgViewer::Viewer  
375. {  
376. public:  
377.     ViewerWidget(osg::Node *scene = NULL)  
378.     {  
379.         QWidget* renderWidget = getRenderWidget( createGraphicsWindow(0,0,100,100), scene);  
380.   
381.         QVBoxLayout* layout = new QVBoxLayout;  
382.         layout->addWidget(renderWidget);  
383.         layout->setContentsMargins(0, 0, 0, 1);  
384.         setLayout( layout );  
385.   
386.         connect( &_timer, SIGNAL(timeout()), this, SLOT(update()) );  
387.         _timer.start( 10 );  
388.     }  
389.   
390.     QWidget* getRenderWidget( osgQt::GraphicsWindowQt* gw, osg::Node* scene )  
391.     {  
392.         osg::Camera* camera = this->getCamera();  
393.         camera->setGraphicsContext( gw );  
394.   
395.         const osg::GraphicsContext::Traits* traits = gw->getTraits();  
396.   
397.         camera->setClearColor( osg::Vec4(0.0, 0.0, 0.0, 0.5) );  
398.         camera->setViewport( new osg::Viewport(0, 0, traits->width, traits->height) );  
399.         camera->setProjectionMatrixAsPerspective(45.0f, static_cast<double>(traits->width)/static_cast<double>(traits->height), 0.1f, 100.0f );  
400.         camera->setViewMatrixAsLookAt(osg::Vec3d(0, 0, 1), osg::Vec3d(0, 0, 0), osg::Vec3d(0, 1, 0));  
401.   
402.         osg::StateSet* globalStateset = camera->getStateSet();  
403.         if (globalStateset)  
404.         {  
405.             osg::LightModel* lightModel = new osg::LightModel;  
406.             lightModel->setAmbientIntensity(osg::Vec4(0,0,0,0));  
407.             globalStateset->setAttributeAndModes(lightModel, osg::StateAttribute::ON);  
408.         }  
409.   
410.         this->setSceneData( scene );  
411.         this->addEventHandler(new ManipulatorSceneHandler());  
412.   
413.         return gw->getGLWidget();  
414.     }  
415.   
416.     osgQt::GraphicsWindowQt* createGraphicsWindow( int x, int y, int w, int h, const std::string& name="", bool windowDecoration=false )  
417.     {  
418.         osg::DisplaySettings* ds = osg::DisplaySettings::instance().get();  
419.         osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;  
420.         traits->windowName = name;  
421.         traits->windowDecoration = windowDecoration;  
422.         traits->x = x;  
423.         traits->y = y;  
424.         traits->width = w;  
425.         traits->height = h;  
426.         traits->doubleBuffer = true;  
427.         traits->alpha = ds->getMinimumNumAlphaBits();  
428.         traits->stencil = ds->getMinimumNumStencilBits();  
429.         traits->sampleBuffers = ds->getMultiSamples();  
430.         traits->samples = ds->getNumMultiSamples();  
431.   
432.         return new osgQt::GraphicsWindowQt(traits.get());  
433.     }  
434.   
435.     virtual void paintEvent( QPaintEvent* event )  
436.     {   
437.         frame();   
438.     }  
439.   
440. protected:  
441.   
442.     QTimer _timer;  
443. };  
444.   
445.   
446.   
447. osg::Node*  buildScene()  
448. {  
449.     osg::Group *root = new osg::Group;  
450.   
451.     osg::Light* light = new osg::Light();  
452.     light->setLightNum(0);  
453.     light->setAmbient(osg::Vec4(0.5f, 0.5f, 0.5f, 1.0f));  
454.     light->setDiffuse(osg::Vec4(1.0f, 1.0f, 1.0f, 1.0f));  
455.     light->setPosition(osg::Vec4(0.0f, 0.0f, 2.0f, 1.0f));  
456.     osg::LightSource* lightsource = new osg::LightSource();  
457.     lightsource->setLight (light);  
458.     root->addChild (lightsource);   
459.   
460.     osg::MatrixTransform *quadMT = new osg::MatrixTransform;  
461.     quadMT->setName("zoomMT");  
462.     quadMT->setMatrix(osg::Matrix::translate(0.0, 0.0, -5.0));  
463.   
464.     osg::MatrixTransform *quadXRotMT = new osg::MatrixTransform;  
465.     quadXRotMT->setName("xRotMT");  
466.     RotateCallback *xRotCallback = new RotateCallback(osg::X_AXIS, 0.0);  
467.     quadXRotMT->setUpdateCallback(xRotCallback);  
468.   
469.   
470.     osg::MatrixTransform *quadYRotMT = new osg::MatrixTransform;  
471.     quadYRotMT->setName("yRotMT");  
472.     RotateCallback *yRotCallback = new RotateCallback(osg::Y_AXIS, 0.0);  
473.     quadYRotMT->setUpdateCallback(yRotCallback);  
474.   
475.     osg::Geometry *quadGeometry = new osg::Geometry;  
476.     osg::Vec3Array *quadVertexArray = new osg::Vec3Array;  
477.     for (unsigned i = 0; i < sizeof(QuadVertices); ++i)  
478.     {  
479.         quadVertexArray->push_back(osg::Vec3(QuadVertices[i][0], QuadVertices[i][1], QuadVertices[i][2]));  
480.     }  
481.     quadGeometry->setVertexArray(quadVertexArray);  
482.   
483.     osg::Vec4Array *colorArray = new osg::Vec4Array;  
484.     colorArray->push_back(osg::Vec4(1.0f, 1.0f, 1.0f, 0.5));  
485.     quadGeometry->setColorArray(colorArray, osg::Array::BIND_OVERALL);  
486.   
487.     osg::BlendFunc *blendFunc = new osg::BlendFunc(GL_SRC_ALPHA, GL_ONE, 0.5, 0.5);  
488.     quadGeometry->getOrCreateStateSet()->setRenderingHint(  
489.         osg::StateSet::TRANSPARENT_BIN );  
490.     quadGeometry->getOrCreateStateSet()->setAttribute(blendFunc,  
491.         osg::StateAttribute::ON);  
492.   
493.     osg::Vec2Array* texcoords = new osg::Vec2Array;  
494.     for (unsigned i = 0; i < sizeof(textureVertices); ++i)  
495.     {  
496.         texcoords->push_back(osg::Vec2(textureVertices[i][0], textureVertices[i][1]));  
497.     }  
498.     quadGeometry->setTexCoordArray(0,texcoords);  
499.   
500.     osg::Vec3Array *quadNormalArray = new osg::Vec3Array;  
501.     for (unsigned i = 0; i < sizeof(normalVertics); ++i)  
502.     {  
503.         quadNormalArray->push_back(osg::Vec3(normalVertics[i][0], normalVertics[i][1], normalVertics[i][2]));  
504.     }  
505.     quadGeometry->setNormalArray(quadNormalArray, osg::Array::BIND_PER_PRIMITIVE_SET);  
506.   
507.     int first = 0;  
508.     for (unsigned i = 0; i < 6; ++i)  
509.     {  
510.         osg::DrawArrays *vertexIndices = new osg::DrawArrays(osg::PrimitiveSet::QUADS, first, 4);  
511.         first += 4;  
512.         quadGeometry->addPrimitiveSet(vertexIndices);  
513.     }  
514.   
515.     osg::Image *textureImage = osgDB::readImageFile("Data/Glass.bmp");  
516.     osg::Texture2D *texture2D = new osg::Texture2D;  
517.     texture2D->setImage(textureImage);  
518.     texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::NEAREST);  
519.     texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::NEAREST);  
520.   
521.     osg::Geode *quadGeode = new osg::Geode;  
522.     quadGeode->setName("quadGeode");  
523.     quadGeode->getOrCreateStateSet()->setTextureAttributeAndModes(0, texture2D);  
524.   
525.     quadGeode->addDrawable(quadGeometry);  
526.     quadYRotMT->addChild(quadGeode);  
527.     quadXRotMT->addChild(quadYRotMT);  
528.     quadMT->addChild(quadXRotMT);  
529.   
530.     root->addChild(quadMT);  
531.   
532.     return root;  
533. }  
534.   
535.   
536.   
537. int main( int argc, char** argv )  
538. {  
539.     QApplication app(argc, argv);  
540.     ViewerWidget* viewWidget = new ViewerWidget(buildScene());  
541.     viewWidget->setGeometry( 100, 100, 640, 480 );  
542.     viewWidget->show();  
543.     return app.exec();  
544. }