用OpenSceneGraph实现的NeHe OpenGL教程 - 第三十四课
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简介
NeHe教程在这节课向我们介绍了如何从一个2D的灰度图创建地形。这节课的内容比较简单，只是从一个2D灰度图中读取灰度数据，然后将灰度数据转换成高度数据，最后将这些数据显示出来就可以了。
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实现
首先读取raw格式的图片，将里面的灰度值转换成Y值：
void LoadRawFile(LPSTR strName, int nSize, BYTE *pHeightMap) //读取灰度图
{
FILE *pFile = NULL;
pFile = fopen( strName, "rb" );
if ( pFile == NULL )
{
return;
}
fread( pHeightMap, 1, nSize, pFile );
int result = ferror( pFile );
fclose(pFile);
}
int Height(BYTE *pHeightMap, int X, int Y) // This Returns The Height From A Height Map Index
{
int x = X % MAP_SIZE; // Error Check Our x Value
int y = Y % MAP_SIZE; // Error Check Our y Value
if(!pHeightMap) return 0; // Make Sure Our Data Is Valid
return pHeightMap[x + (y * MAP_SIZE)]; // Index Into Our Height Array And Return The Height
}读取完成之后，创建整个网格：
osg::Geode* RenderHeightMap(BYTE pHeightMap[])
最后在与鼠标的交互中切换显示的模式：
case(osgGA::GUIEventAdapter::PUSH):
{
if (ea.getButtonMask() == osgGA::GUIEventAdapter::LEFT_MOUSE_BUTTON)
{
if (!g_TerrainGeometry)
return false;
osg::Vec3Array *vertexArray = dynamic_cast<osg::Vec3Array*>(g_TerrainGeometry->getVertexArray());
if (!vertexArray)
return false;
static bool flag = true;
if (flag){
g_TerrainGeometry->setPrimitiveSet(0, new osg::DrawArrays(osg::PrimitiveSet::LINES, 0, vertexArray->size()));
flag = !flag;
} else {
g_TerrainGeometry->setPrimitiveSet(0, new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));
flag = !flag;
}
}
}将所有部分添加到场景，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>
#define MAP_SIZE 1024
#define STEP_SIZE 16
#define HEIGHT_RATIO 1.5f
BYTE g_HeightMap[MAP_SIZE*MAP_SIZE];
float scaleValue = 0.15f;
osg::Geometry *g_TerrainGeometry = NULL;
void LoadRawFile(LPSTR strName, int nSize, BYTE *pHeightMap)
{
FILE *pFile = NULL;
pFile = fopen( strName, "rb" );
if ( pFile == NULL )
{
return;
}
fread( pHeightMap, 1, nSize, pFile );
int result = ferror( pFile );
fclose(pFile);
}
int Height(BYTE *pHeightMap, int X, int Y) // This Returns The Height From A Height Map Index
{
int x = X % MAP_SIZE; // Error Check Our x Value
int y = Y % MAP_SIZE; // Error Check Our y Value
if(!pHeightMap) return 0; // Make Sure Our Data Is Valid
return pHeightMap[x + (y * MAP_SIZE)]; // Index Into Our Height Array And Return The Height
}
osg::Vec3 SetVertexColor(BYTE *pHeightMap, int x, int y)
{
float fColor = -0.15f + (Height(pHeightMap, x, y ) / 256.0f);
return osg::Vec3(0, 0, fColor );
}
osg::Geode* RenderHeightMap(BYTE pHeightMap[])
{
int X = 0, Y = 0;
int x, y=0, z;
osg::Geode *terrainGeode = new osg::Geode;
osg::Geometry *terrainGeomety = new osg::Geometry;
osg::Vec3Array *vertexArray = new osg::Vec3Array;
osg::Vec3Array *colorArray = new osg::Vec3Array;
for ( X = 0; X < (MAP_SIZE-STEP_SIZE); X += STEP_SIZE )
for ( Y = 0; Y < (MAP_SIZE-STEP_SIZE); Y += STEP_SIZE )
{
//左下点坐标
x = X;
y = Height(pHeightMap, X, Y );
z = Y;
vertexArray->push_back(osg::Vec3(x, y, z));
osg::Vec3 colorLeftBottom = SetVertexColor(pHeightMap, x, z);
colorArray->push_back(colorLeftBottom);
//左上点坐标
x = X;
y = Height(pHeightMap, X, Y + STEP_SIZE );
z = Y + STEP_SIZE ;
vertexArray->push_back(osg::Vec3(x, y, z));
osg::Vec3 colorLeftTop = SetVertexColor(pHeightMap, x, z);
colorArray->push_back(colorLeftTop);
// 右上点坐标
x = X + STEP_SIZE;
y = Height(pHeightMap, X + STEP_SIZE, Y + STEP_SIZE );
z = Y + STEP_SIZE ;
vertexArray->push_back(osg::Vec3(x, y, z));
osg::Vec3 colorRightTop = SetVertexColor(pHeightMap, x, z);
colorArray->push_back(colorRightTop);
// Get The (X, Y, Z) Value For The Bottom Right Vertex
x = X + STEP_SIZE;
y = Height(pHeightMap, X + STEP_SIZE, Y );
z = Y;
vertexArray->push_back(osg::Vec3(x, y, z));
osg::Vec3 colorRightBottom = SetVertexColor(pHeightMap, x, z);
colorArray->push_back(colorRightBottom);
}
terrainGeomety->setVertexArray(vertexArray);
terrainGeomety->setColorArray(colorArray, osg::Array::BIND_PER_VERTEX);
terrainGeomety->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));
terrainGeomety->getOrCreateStateSet()->setMode(GL_LIGHTING, osg::StateAttribute::OFF);
g_TerrainGeometry = terrainGeomety;
terrainGeode->addDrawable(terrainGeomety);
return terrainGeode;
}
//////////////////////////////////////////////////////////////////////////
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::PUSH):
{
if (ea.getButtonMask() == osgGA::GUIEventAdapter::LEFT_MOUSE_BUTTON)
{
if (!g_TerrainGeometry)
return false;
osg::Vec3Array *vertexArray = dynamic_cast<osg::Vec3Array*>(g_TerrainGeometry->getVertexArray());
if (!vertexArray)
return false;
static bool flag = true;
if (flag){
g_TerrainGeometry->setPrimitiveSet(0, new osg::DrawArrays(osg::PrimitiveSet::LINES, 0, vertexArray->size()));
flag = !flag;
} else {
g_TerrainGeometry->setPrimitiveSet(0, new osg::DrawArrays(osg::PrimitiveSet::QUADS, 0, vertexArray->size()));
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(0.0f, 0.0f, 0.0f, 0.5f) );
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(212, 60, 194), osg::Vec3d(186, 55, 171), 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()
{
LoadRawFile("Data/Terrain.raw", MAP_SIZE * MAP_SIZE, g_HeightMap);
osg::Group *root = new osg::Group;
osg::MatrixTransform *scaleMT = new osg::MatrixTransform;
scaleMT->setMatrix(osg::Matrix::scale(scaleValue, scaleValue * HEIGHT_RATIO, scaleValue));
scaleMT->addChild(RenderHeightMap(g_HeightMap));
root->addChild(scaleMT);
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();
}