未用shader的效果：

使用shader後的效果：

./data/myFrag.frag

    uniform sampler2D texUnit0;

    void main(){
        //texUnit0由外面呼叫程式傳進來，gl_TexCoord[]輸入紋理座標陣列；這句話的意思 從紋理取樣器texUnit0中取得紋理座標對應的紋理畫素值。
        vec4 color = texture2D(texUnit0,gl_TexCoord[0].xy); 
        
        //簡單的將這三個顏色值相加。
        float gcolor = color.r+color.g+color.b;
        
 
//灰度值輸出（gl_FragColor是每個片元著色器必須設定的輸出）
        gl_FragColor = vec4(gcolor,gcolor,gcolor,color.a);
    }

main.cpp

#include <osgViewer/Viewer>

#include <osg/Node>
#include <osg/Geode>
#include <osg/Group>
#include <osg/ShapeDrawable>

#include <osgDB/ReadFile>
#include 
 
<osgDB/WriteFile>

#include <osgUtil/Optimizer>

//繪製多個預定義的幾何體
osg::ref_ptr<osg::Geode> createShape()
{
    //建立一個葉節點
    osg::ref_ptr<osg::Geode> geode = new osg::Geode();

    //設定半徑和高度
    float radius = 0.8f;
    float height = 1.0f;

    //建立精細度物件，精細度越高，細分就越多
    osg::ref_ptr<osg::TessellationHints> hints = new
 
 osg::TessellationHints;
    //設定精細度為0.5f
    hints->setDetailRatio(0.5f);

    //新增一個球體，第一個引數是預定義幾何體物件，第二個是精細度，預設為0
    geode->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0.0f,0.0f,0.0f),radius),hints.get()));
    //新增一個正方體
    geode->addDrawable(new osg::ShapeDrawable(new osg::Box(osg::Vec3(2.0f,0.0f,0.0f),2*radius),hints.get()));

    return geode.get() ;
}

int main()
{
    //建立Viewer物件，場景瀏覽器
    osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();

    osg::ref_ptr<osg::Group> root = new osg::Group();

    //新增到場景
    osg::ref_ptr<osg::Group> myGroup = new osg::Group;
    myGroup->addChild(createShape());
    myGroup->getOrCreateStateSet()->setTextureAttribute( 0,new osg::Texture2D(osgDB::readImageFile("C:\\55.jpg")));
    myGroup->getOrCreateStateSet()->setTextureMode(0,GL_TEXTURE_2D,osg::StateAttribute::ON);

    /************************使用片元著色器************************************/
    osg::ref_ptr<osg::StateSet> ss = myGroup->getOrCreateStateSet();

    //new一個屬性類，用於新增屬性，
    osg::ref_ptr<osg::Program> texProgram = new osg::Program;
    
    //new一個片元著色器
    osg::ref_ptr<osg::Shader> texFragObj = new osg::Shader(osg::Shader::FRAGMENT);

    texFragObj->loadShaderSourceFromFile("./data/myFrag.frag");
    texProgram->addShader(texFragObj);

    //傳參   形參是texUnit0  0作為實參
    osg::ref_ptr<osg::Uniform> texUniform = new osg::Uniform("texUnit0",0);

    ss->setAttributeAndModes(texProgram);
    ss->addUniform(texUniform);

    root->addChild(myGroup.get());
    /************************使用片元著色器************************************/
    //優化場景資料
    osgUtil::Optimizer optimizer ;
    optimizer.optimize(root.get()) ;

    viewer->setSceneData(root.get());
    viewer->setUpViewInWindow(20,20,600,600);

    viewer->realize();

    viewer->run();

    return 0 ;
}