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用OpenSceneGraph实现的NeHe OpenGL教程 - 第三十五课

2014-05-28 10:31 295 查看

简介

这节课介绍了如何在三维场景中类似播放一段视频的效果。我们都知道视频实际上是由一帧帧的图片来构成的,因此我们将视频中的图片解析成图片格式,并将这些图片赋给几何体表面,让它们在很短的间隔内进行切换就实现了动态的效果。

实现

本课中使用了Windows解析视频格式***I文件的API,代码中这部分内容都来自NeHe课程中的相应代码,读者可以查阅MSDN了解这些内容:

首先创建播放***I文件的几何体(类似于电影的大屏幕)

osg::Geode*	createBackGroundGeode(osg::Texture2D *text)
{
    osg::Geode *geode = new osg::Geode;
    osg::Geometry *geometry = new osg::Geometry;
    geometry->setUpdateCallback(new DynamicTextureUpdateCallback);
 ...
	geometry->setVertexArray(vertexArray);
	geometry->setTexCoordArray(0, textureArray, osg::Array::BIND_PER_VERTEX);
	geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));
	geometry->getOrCreateStateSet()->setTextureAttributeAndModes(0, text);
	geometry->getOrCreateStateSet()->setMode(GL_LIGHTING, false);
	geode->addDrawable(geometry);

	return geode;
}
动态的纹理回调DynamicTextureUpdateCallback实现了动态修改纹理:

class DynamicTextureUpdateCallback : public osg::Drawable::UpdateCallback
{
public:
	DynamicTextureUpdateCallback() : _lastUpdate(0), _frame(0), _passedTimeInMillSecond(0)
	{
		_startTime = osg::Timer::instance()->tick(); 
		_currentTime = _startTime;
	}

	void update(osg::NodeVisitor* nv, osg::Drawable* drawable)
	{
		osg::Geometry *geometry = dynamic_cast<osg::Geometry*>(drawable);
		if (!geometry)
...
        }
};
接着创建场景中的几何体:

osg::Node*	createBox()
osg::Node*	createSphere()
osg::Node*	createCylinder()
这部分内容与第二十三课的内容很类似

将上面所有的几何体添加到一个Switch开关节点中实现切换操作:

在与键盘的交互中实现切换纹理方式和切换节点的效果:

case(osgGA::GUIEventAdapter::KEYDOWN):
			{
				if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Space)
				{
					if (!g_SwitchNode)
						return false;

					static int i = 0;
					++i;
					if (i > 2)
						i = 0;
					g_SwitchNode->setSingleChildOn(i);
				}
				if (ea.getKey() == osgGA::GUIEventAdapter::KEY_E)
				{
					static bool flag = true;
					if(flag){
						g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_S, osg::StateAttribute::OFF);
						g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_T, osg::StateAttribute::OFF);
					}else{
						g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_S, osg::StateAttribute::ON);
						g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_T, osg::StateAttribute::ON);
					}
					flag = !flag;
				}
将以上所有内容添加到场景根节点下。编译运行程序:



附:本课源码(源码中可能存在错误和不足,仅供参考)

#include "../osgNeHe.h"

#include <QtCore/QTimer>
#include <QtGui/QApplication>
#include <QtGui/QVBoxLayout>

#include <osgViewer/Viewer>
#include <osgDB/ReadFile>
#include <osgQt/GraphicsWindowQt>
#include <osg/MatrixTransform>
#include <osg/Texture2D>
#include <osg/ShapeDrawable>

#include <osg/Switch>
#include <osg/AnimationPath>

#include <osg/TexGen>
#include <osg/TexGenNode>

#include <vfw.h>

***ISTREAMINFO psi;
P***ISTREAM pavi;
PGETFRAME pgf;
BITMAPINFOHEADER bmih;
long lastframe;
int width;
int height;
char *pdata;
int mpf;

HDRAWDIB hdd;
HBITMAP hBitmap;
HDC hdc = CreateCompatibleDC(0);
unsigned char* data = 0;

osg::Texture2D *g_Texture2D = NULL;
osg::Image *g_TextureImage = NULL;
osg::Switch *g_SwitchNode = NULL;

void flipIt(void* buffer)
{
void* b = buffer;
__asm
{
mov ecx, 256*256
mov ebx, b
label:
mov al,[ebx+0]
mov ah,[ebx+2]
mov [ebx+2],al
mov [ebx+0],ah

add ebx,3
dec ecx
jnz label
}
}

void Open***I(LPCSTR szFile)
{
TCHAR title[100];

***IFileInit();
if (***IStreamOpenFromFileA(&pavi, szFile, streamtypeVIDEO, 0, OF_READ, NULL) !=0)
{
return;
}

***IStreamInfo(pavi, &psi, sizeof(psi));
width=psi.rcFrame.right-psi.rcFrame.left;
height=psi.rcFrame.bottom-psi.rcFrame.top;

lastframe=***IStreamLength(pavi);

mpf=***IStreamSampleToTime(pavi,lastframe)/lastframe;

bmih.biSize = sizeof (BITMAPINFOHEADER);
bmih.biPlanes = 1;
bmih.biBitCount = 24;
bmih.biWidth = 256;
bmih.biHeight = 256;
bmih.biCompression = BI_RGB;

hBitmap = CreateDIBSection (hdc, (BITMAPINFO*)(&bmih), DIB_RGB_COLORS, (void**)(&data), NULL, NULL);
SelectObject (hdc, hBitmap);

pgf=***IStreamGetFrameOpen(pavi, NULL);
if (pgf==NULL)
{
return;
}
}

void Grab***IFrame(int frame)
{
LPBITMAPINFOHEADER lpbi;
lpbi = (LPBITMAPINFOHEADER)***IStreamGetFrame(pgf, frame);
pdata=(char *)lpbi+lpbi->biSize+lpbi->biClrUsed * sizeof(RGBQUAD);

DrawDibDraw (hdd, hdc, 0, 0, 256, 256, lpbi, pdata, 0, 0, width, height, 0);
flipIt(data);

g_TextureImage->setImage(256, 256, 1, 3, GL_RGB, GL_UNSIGNED_BYTE, data, osg::Image::NO_DELETE);
g_Texture2D->setImage(g_TextureImage);
}

void Close***I(void)
{
DeleteObject(hBitmap);
DrawDibClose(hdd);
***IStreamGetFrameClose(pgf);
***IStreamRelease(pavi);
***IFileExit();
}

void initialize()
{
hdd = DrawDibOpen();
g_Texture2D = new osg::Texture2D;
g_Texture2D->setFilter(osg::Texture::MAG_FILTER, osg::Texture::NEAREST);
g_Texture2D->setFilter(osg::Texture::MIN_FILTER, osg::Texture::NEAREST);
g_TextureImage = new osg::Image;
g_TextureImage->allocateImage(256, 256, 1, GL_RGB, GL_UNSIGNED_BYTE);
Open***I("Data/face3.avi");
}

class DynamicTextureUpdateCallback : public osg::Drawable::UpdateCallback
{
public:
DynamicTextureUpdateCallback() : _lastUpdate(0), _frame(0), _passedTimeInMillSecond(0)
{
_startTime = osg::Timer::instance()->tick();
_currentTime = _startTime;
}

void update(osg::NodeVisitor* nv, osg::Drawable* drawable)
{
osg::Geometry *geometry = dynamic_cast<osg::Geometry*>(drawable);
if (!geometry)
return;
osg::Texture2D *texture2D = dynamic_cast<osg::Texture2D *>(geometry->getOrCreateStateSet()->getTextureAttribute(
0, osg::StateAttribute::TEXTURE));
if (!texture2D)
return;

if (nv->getVisitorType() == osg::NodeVisitor::UPDATE_VISITOR &&
nv->getFrameStamp() &&
nv->getFrameStamp()->getFrameNumber() != _lastUpdate)
{
_lastUpdate = nv->getFrameStamp()->getFrameNumber();
_currentTime = osg::Timer::instance()->tick();
float t = osg::Timer::instance()->delta_m(_startTime, _currentTime);
_passedTimeInMillSecond += t;

if (_passedTimeInMillSecond >= mpf)
{
Grab***IFrame(_frame);
_frame++;

if (_frame >= lastframe)
{
_frame = 0;
}
_passedTimeInMillSecond = 0;
}
}
}

osg::Timer_t _startTime;
osg::Timer_t _currentTime;
unsigned int _lastUpdate;
unsigned int _frame;
int _passedTimeInMillSecond;
};

//////////////////////////////////////////////////////////////////////////
///////////////////////绘制几何体/////////////////////////////////
//////////////////////////////////////////////////////////////////////////
osg::Geode* createBackGroundGeode(osg::Texture2D *text)
{
osg::Geode *geode = new osg::Geode;
osg::Geometry *geometry = new osg::Geometry;
geometry->setUpdateCallback(new DynamicTextureUpdateCallback);
osg::Vec3Array *vertexArray = new osg::Vec3Array;
osg::Vec2Array *textureArray = new osg::Vec2Array;

vertexArray->push_back(osg::Vec3(11.0f, 8.3f, -20.0f));
vertexArray->push_back(osg::Vec3(-11.0f, 8.3f, -20.0f));
vertexArray->push_back(osg::Vec3(-11.0f, -8.3f, -20.0f));
vertexArray->push_back(osg::Vec3(11.0f, -8.3f, -20.0f));

textureArray->push_back(osg::Vec2(1.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));

geometry->setVertexArray(vertexArray);
geometry->setTexCoordArray(0, textureArray, osg::Array::BIND_PER_VERTEX);
geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));
geometry->getOrCreateStateSet()->setTextureAttributeAndModes(0, text);
geometry->getOrCreateStateSet()->setMode(GL_LIGHTING, false);
geode->addDrawable(geometry);

return geode;
}

osg::Node* createBox(/*osg::Texture2D *text*/)
{
osg::MatrixTransform *mtX = new osg::MatrixTransform;
mtX->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::X_AXIS, 1.5));
osg::MatrixTransform *mtY = new osg::MatrixTransform;
mtY->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Y_AXIS, 2.5));
osg::MatrixTransform *mtZ = new osg::MatrixTransform;
mtZ->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Z_AXIS, 3.5));

osg::Geode *geode = new osg::Geode;
osg::Geometry *geometry = new osg::Geometry;
osg::Vec3Array *vertexArray = new osg::Vec3Array;
osg::Vec2Array *textureArray = new osg::Vec2Array;
osg::Vec3Array *normalArray = new osg::Vec3Array;

for (int i = 0; i < 4; ++i)
normalArray->push_back(osg::Vec3(0.0f, 0.0f, 0.5f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, -1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(1.0f, -1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(1.0f, 1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, 1.0f, 1.0f));

for (int i = 0; i < 4; ++i)
normalArray->push_back(osg::Vec3(0.0f, 0.0f,-0.5f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
vertexArray->push_back(osg::Vec3(-1.0f, -1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, 1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(1.0f, 1.0f, - 1.0f));
vertexArray->push_back(osg::Vec3(1.0f, -1.0f, -1.0f));

for (int i = 0; i < 4; ++i)
normalArray->push_back(osg::Vec3(0.0f, 0.5f,0.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, 1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, 1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(1.0f, 1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(1.0f, 1.0f, -1.0f));

for (int i = 0; i < 4; ++i)
normalArray->push_back(osg::Vec3(0.0f, -0.5f,0.0f));
textureArray->push_back(osg::Vec2(1.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));
vertexArray->push_back(osg::Vec3(-1.0f, -1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(1.0f, -1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(1.0f, -1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, -1.0f, 1.0f));

for (int i = 0; i < 4; ++i)
normalArray->push_back(osg::Vec3(0.5f, 0.0f,0.0f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
vertexArray->push_back(osg::Vec3(1.0f, -1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(1.0f, 1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(1.0f, 1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(1.0f, -1.0f, 1.0f));

for (int i = 0; i < 4; ++i)
normalArray->push_back(osg::Vec3(-0.5f, 0.0f,0.0f));
textureArray->push_back(osg::Vec2(0.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 0.0f));
textureArray->push_back(osg::Vec2(1.0f, 1.0f));
textureArray->push_back(osg::Vec2(0.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, -1.0f, -1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, -1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, 1.0f, 1.0f));
vertexArray->push_back(osg::Vec3(-1.0f, 1.0f, -1.0f));

geometry->setVertexArray(vertexArray);
geometry->setNormalArray(normalArray, osg::Array::BIND_PER_VERTEX);
geometry->setTexCoordArray(0, textureArray, osg::Array::BIND_PER_VERTEX);
geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));
geometry->getOrCreateStateSet()->setMode(GL_LIGHTING, false);
geode->addDrawable(geometry);

mtX->addChild(mtY);
mtY->addChild(mtZ);
mtZ->addChild(geode);

return mtX;
}

osg::Node* createSphere()
{
osg::MatrixTransform *mtX = new osg::MatrixTransform;
mtX->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::X_AXIS, 1.5));
osg::MatrixTransform *mtY = new osg::MatrixTransform;
mtY->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Y_AXIS, 2.5));
osg::MatrixTransform *mtZ = new osg::MatrixTransform;
mtZ->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Z_AXIS, 3.5));

osg::Geode *sphere = new osg::Geode;
osg::ShapeDrawable *sphereDrawable = new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0,0,0), 1.3));
sphere->addDrawable(sphereDrawable);

mtX->addChild(mtY);
mtY->addChild(mtZ);
mtZ->addChild(sphere);

return mtX;
}

osg::Node* createCylinder()
{
osg::MatrixTransform *mtX = new osg::MatrixTransform;
mtX->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::X_AXIS, 1.5));
osg::MatrixTransform *mtY = new osg::MatrixTransform;
mtY->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Y_AXIS, 2.5));
osg::MatrixTransform *mtZ = new osg::MatrixTransform;
mtZ->addUpdateCallback(new osg::AnimationPathCallback(osg::Vec3(), osg::Z_AXIS, 3.5));

osg::Geode *cylinder = new osg::Geode;
osg::ShapeDrawable *cylinderDrawable = new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0,0,0), 0.5, 2.0));
cylinder->addDrawable(cylinderDrawable);

mtX->addChild(mtY);
mtY->addChild(mtZ);
mtZ->addChild(cylinder);

return mtX;
}

//////////////////////////////////////////////////////////////////////////
/////////////////////////////场景交互//////////////////////////////
//////////////////////////////////////////////////////////////////////////
class ManipulatorSceneHandler : public osgGA::GUIEventHandler
{
public:
ManipulatorSceneHandler()
{
}

virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)
{
osgViewer::Viewer *viewer = dynamic_cast<osgViewer::Viewer*>(&aa);
if (!viewer)
return false;
if (!viewer->getSceneData())
return false;
if (ea.getHandled())
return false;

switch(ea.getEventType())
{
case(osgGA::GUIEventAdapter::KEYDOWN): { if (ea.getKey() == osgGA::GUIEventAdapter::KEY_Space) { if (!g_SwitchNode) return false; static int i = 0; ++i; if (i > 2) i = 0; g_SwitchNode->setSingleChildOn(i); } if (ea.getKey() == osgGA::GUIEventAdapter::KEY_E) { static bool flag = true; if(flag){ g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_S, osg::StateAttribute::OFF); g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_T, osg::StateAttribute::OFF); }else{ g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_S, osg::StateAttribute::ON); g_SwitchNode->getOrCreateStateSet()->setTextureMode(0, GL_TEXTURE_GEN_T, osg::StateAttribute::ON); } flag = !flag; }
}
default: break;
}
return false;
}
};
//////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////
//////////////////////////osgNeHe框架////////////////////////////
//////////////////////////////////////////////////////////////////////////
class ViewerWidget : public QWidget, public osgViewer::Viewer
{
public:
ViewerWidget(osg::Node *scene = NULL)
{
QWidget* renderWidget = getRenderWidget( createGraphicsWindow(0,0,100,100), scene);

QVBoxLayout* layout = new QVBoxLayout;
layout->addWidget(renderWidget);
layout->setContentsMargins(0, 0, 0, 1);
setLayout( layout );

connect( &_timer, SIGNAL(timeout()), this, SLOT(update()) );
_timer.start( 10 );
}

QWidget* getRenderWidget( osgQt::GraphicsWindowQt* gw, osg::Node* scene )
{
osg::Camera* camera = this->getCamera();
camera->setGraphicsContext( gw );

const osg::GraphicsContext::Traits* traits = gw->getTraits();

camera->setClearColor( osg::Vec4(0.0, 0.0, 0.0, 1.0) );
camera->setViewport( new osg::Viewport(0, 0, traits->width, traits->height) );
camera->setProjectionMatrixAsPerspective(45.0f, static_cast<double>(traits->width)/static_cast<double>(traits->height), 0.1f, 100.0f );
camera->setViewMatrixAsLookAt(osg::Vec3d(0, 0, 0), osg::Vec3d(0, 0, -1), osg::Vec3d(0, 1, 0));

this->setSceneData( scene );
this->addEventHandler(new ManipulatorSceneHandler);

return gw->getGLWidget();
}

osgQt::GraphicsWindowQt* createGraphicsWindow( int x, int y, int w, int h, const std::string& name="", bool windowDecoration=false )
{
osg::DisplaySettings* ds = osg::DisplaySettings::instance().get();
osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
traits->windowName = name;
traits->windowDecoration = windowDecoration;
traits->x = x;
traits->y = y;
traits->width = w;
traits->height = h;
traits->doubleBuffer = true;
traits->alpha = ds->getMinimumNumAlphaBits();
traits->stencil = ds->getMinimumNumStencilBits();
traits->sampleBuffers = ds->getMultiSamples();
traits->samples = ds->getNumMultiSamples();

return new osgQt::GraphicsWindowQt(traits.get());
}

virtual void paintEvent( QPaintEvent* event )
{
frame();
}

protected:

QTimer _timer;
};

osg::Node* buildScene()
{
initialize();

osg::Group *root = new osg::Group;

osg::Switch *switchNode = new osg::Switch;
g_SwitchNode = switchNode;
switchNode->addChild(createBox());
switchNode->addChild(createCylinder());
switchNode->addChild(createSphere());
switchNode->setSingleChildOn(0);

osg::TexGen *texGen = new osg::TexGen;
texGen->setMode(osg::TexGen::SPHERE_MAP);
switchNode->getOrCreateStateSet()->setTextureAttributeAndModes(0, texGen);
switchNode->getOrCreateStateSet()->setTextureAttributeAndModes(0, g_Texture2D);

osg::MatrixTransform *zoomMT = new osg::MatrixTransform;
zoomMT->setMatrix(osg::Matrix::translate(0.0f, 0.0f, -10.0f));
zoomMT->addChild(switchNode);

root->addChild(createBackGroundGeode(g_Texture2D));
root->addChild(zoomMT);
return root;
}

int main( int argc, char** argv )
{
QApplication app(argc, argv);
ViewerWidget* viewWidget = new ViewerWidget(buildScene());
viewWidget->setGeometry( 100, 100, 640, 480 );
viewWidget->show();
return app.exec();
}
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