Learning OSG programing---osgShape

本例示范了osg中Shape ---- 基本几何元素的绘制过程。参照osg官方文档，Shape 类包含以下子类：

在示例程序中，函数createShapes函数用于生成需要绘制的几何形状。

 osg::Geode* createShapes(osg::ArgumentParser& arguments)

 {

     osg::Geode* geode = new osg::Geode();

     // ---------------------------------------

     // Set up a StateSet to texture the objects

     // ---------------------------------------

     osg::StateSet* stateset = new osg::StateSet();

 　　//设置材质图片

     osg::ref_ptr<osg::Image> image = osgDB::readRefImageFile( "Images/lz.rgb" );

     if (image)

     {

         osg::Texture2D* texture = new osg::Texture2D;

         texture->setImage(image);

         texture->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR);

         stateset->setTextureAttributeAndModes(,texture, osg::StateAttribute::ON);

     }

     stateset->setMode(GL_LIGHTING, osg::StateAttribute::ON);

     geode->setStateSet( stateset );

     float radius = 0.8f;

     float height = 1.0f;

     osg::TessellationHints* hints = new osg::TessellationHints;

     hints->setDetailRatio(0.5f);

 　　//建立各种几何实体

     geode->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0.0f,0.0f,0.0f),radius),hints));

     geode->addDrawable(new osg::ShapeDrawable(new osg::Box(osg::Vec3(2.0f,0.0f,0.0f),*radius),hints));

     geode->addDrawable(new osg::ShapeDrawable(new osg::Cone(osg::Vec3(4.0f,0.0f,0.0f),radius,height),hints));

     geode->addDrawable(new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(6.0f,0.0f,0.0f),radius,height),hints));

     geode->addDrawable(new osg::ShapeDrawable(new osg::Capsule(osg::Vec3(8.0f,0.0f,0.0f),radius,height),hints));

 　　//用于控制平面的高程起伏

     osg::HeightField* grid = new osg::HeightField;

     if (arguments.read("--large"))　　　　　　//大范围

     {

         unsigned int numX = ;

         unsigned int numY = ;

         double sizeX = 10.0;

         double sizeY = 10.0;

         grid->allocate(numX,numY);

         grid->setXInterval(sizeX/float(numX));

         grid->setYInterval(sizeY/float(numY));

         for(unsigned int r=;r<numY;++r)

         {

             for(unsigned int c=;c<numX;++c)

             {

                 double rx = double(c)/double(numX-);

                 double ry = double(r)/double(numY-);

                 grid->setHeight(c, r, 2.0*sin(rx*ry*4.0*osg::PI));

             }

         }

     }

     else　　　　　　　　　　　　　　//小范围

     {

         grid->allocate(,);

         grid->setXInterval(0.28f);

         grid->setYInterval(0.28f);

         for(unsigned int r=;r<;++r)

         {

             for(unsigned int c=;c<;++c)

             {

                 grid->setHeight(c,r,vertex[r+c*][]);

             }

         }

     }

     geode->addDrawable(new osg::ShapeDrawable(grid));

     return geode;

 }

在以上代码中，首先建立了几何节点Geode，加载纹理图像，并将其设置为节点的材质。

之后向节点中加入各种Shape模型，设置它们的集合参数。之后建立了高程域模型osg::HeightField* grid,根据运行程序时提供的命令行参数，设置其为不同的点密度。若运行命令中提供有--large选项，则建立高密度高程集，两层for循环中嵌套的语句，即为计算高程网格中各点的高程值方程。对于large情形，其在点（x,y）处的高程值为2*sin(x*y*4π)。而在普通情况下，点的高程值取决与vertex向量的第三个分量，因为在文件的开始，包含了地形坐标数据：

#include "../osghangglide/terrain_coords.h"

最后，将定义的地形平面添加到节点中去。

在主函数中，调用上面定义的createShapes函数，在进行一些其他准备工作即可：

int main(int argc, char **argv)

{

    osg::ArgumentParser arguments(&argc,argv);

    // construct the viewer.

    osgViewer::Viewer viewer(arguments);

    // add model to viewer.

    viewer.setSceneData( createShapes(arguments) );

    // add the state manipulator

    viewer.addEventHandler( new osgGA::StateSetManipulator(viewer.getCamera()->getOrCreateStateSet()) );

    return viewer.run();

}

按不同模式运行程序，得到不同的效果：

--large模式：

正常模式：

由此程序受到启发，可利用osg高程域，建立DEM（数字高程模型）浏览或仿真、编辑工具，达到学以致用的目的。

Enjoy!