osg天空

http://hi.baidu.com/janxhuilk/blog/item/7a16871b2bd941fbae5133af.html/cmtid/eb8393b4a19d267b8ad4b217

osg::TextureCubeMap* readCubeMap()
{
osg::TextureCubeMap* cubemap = new osg::TextureCubeMap;
//#define CUBEMAP_FILENAME(face) "nvlobby_" #face ".png"
//#define CUBEMAP_FILENAME(face) "Cubemap_axis/" #face ".png"
#define CUBEMAP_FILENAME(face) "res/" #face ".bmp"

osg::Image* imagePosX = osgDB::readImageFile(CUBEMAP_FILENAME(front));
osg::Image* imageNegX = osgDB::readImageFile(CUBEMAP_FILENAME(left));
osg::Image* imagePosY = osgDB::readImageFile(CUBEMAP_FILENAME(down));
osg::Image* imageNegY = osgDB::readImageFile(CUBEMAP_FILENAME(right));
osg::Image* imagePosZ = osgDB::readImageFile(CUBEMAP_FILENAME(up));
osg::Image* imageNegZ = osgDB::readImageFile(CUBEMAP_FILENAME(back));

if (imagePosX && imageNegX && imagePosY /*&& imageNegY && imagePosZ && imageNegZ*/)
{
   cubemap->setImage(osg::TextureCubeMap::POSITIVE_X, imagePosX);
   cubemap->setImage(osg::TextureCubeMap::NEGATIVE_X, imageNegX);
   cubemap->setImage(osg::TextureCubeMap::POSITIVE_Y, imagePosY);
   cubemap->setImage(osg::TextureCubeMap::NEGATIVE_Y, imageNegY);
   cubemap->setImage(osg::TextureCubeMap::POSITIVE_Z, imagePosZ);
   cubemap->setImage(osg::TextureCubeMap::NEGATIVE_Z, imageNegZ);

   cubemap->setWrap(osg::Texture::WRAP_S, osg::Texture::CLAMP_TO_EDGE);
   cubemap->setWrap(osg::Texture::WRAP_T, osg::Texture::CLAMP_TO_EDGE);
   cubemap->setWrap(osg::Texture::WRAP_R, osg::Texture::CLAMP_TO_EDGE);

   cubemap->setFilter(osg::Texture::MIN_FILTER, osg::Texture::LINEAR_MIPMAP_LINEAR);
   cubemap->setFilter(osg::Texture::MAG_FILTER, osg::Texture::LINEAR);
}

return cubemap;
}

// Update texture matrix for cubemaps
struct TexMatCallback : public osg::NodeCallback
{
public:

TexMatCallback(osg::TexMat& tm) :
    _texMat(tm)
    {
    }

    virtual void operator()(osg::Node* node, osg::NodeVisitor* nv)
    {
     osgUtil::CullVisitor* cv = dynamic_cast<osgUtil::CullVisitor*>(nv);
     if (cv)
     {
      const osg::Matrix& MV = cv->getModelViewMatrix();
      const osg::Matrix R = osg::Matrix::rotate( osg::DegreesToRadians(112.0f), 0.0f,0.0f,1.0f)*
       osg::Matrix::rotate( osg::DegreesToRadians(90.0f), 1.0f,0.0f,0.0f);

      osg::Quat q = MV.getRotate();
      const osg::Matrix C = osg::Matrix::rotate( q.inverse() );

      _texMat.setMatrix( C*R );
     }

     traverse(node,nv);
    }

    osg::TexMat& _texMat;
};

class MoveEarthySkyWithEyePointTransform : public osg::Transform
{
public:
/** Get the transformation matrix which moves from local coords to world coords.*/
virtual bool computeLocalToWorldMatrix(osg::Matrix& matrix,osg::NodeVisitor* nv) const
{
   osgUtil::CullVisitor* cv = dynamic_cast<osgUtil::CullVisitor*>(nv);
   if (cv)
   {
    osg::Vec3 eyePointLocal = cv->getEyeLocal();
    matrix.preMult(osg::Matrix::translate(eyePointLocal));
   }
   return true;
}

/** Get the transformation matrix which moves from world coords to local coords.*/
virtual bool computeWorldToLocalMatrix(osg::Matrix& matrix,osg::NodeVisitor* nv) const
{
   osgUtil::CullVisitor* cv = dynamic_cast<osgUtil::CullVisitor*>(nv);
   if (cv)
   {
    osg::Vec3 eyePointLocal = cv->getEyeLocal();
    matrix.postMult(osg::Matrix::translate(-eyePointLocal));
   }
   return true;
}
};

osg::Node* createSkyBox()
{

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

osg::TexEnv* te = new osg::TexEnv;
te->setMode(osg::TexEnv::REPLACE);
stateset->setTextureAttributeAndModes(0, te, osg::StateAttribute::ON);

osg::TexGen *tg = new osg::TexGen;
tg->setMode(osg::TexGen::NORMAL_MAP);
stateset->setTextureAttributeAndModes(0, tg, osg::StateAttribute::ON);

osg::TexMat *tm = new osg::TexMat;
stateset->setTextureAttribute(0, tm);

osg::TextureCubeMap* skymap = readCubeMap();
stateset->setTextureAttributeAndModes(0, skymap, osg::StateAttribute::ON);

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

// clear the depth to the far plane.
osg::Depth* depth = new osg::Depth;
depth->setFunction(osg::Depth::ALWAYS);
depth->setRange(1.0,1.0);   
stateset->setAttributeAndModes(depth, osg::StateAttribute::ON );

stateset->setRenderBinDetails(-1,"RenderBin");

osg::Drawable* drawable = new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(0.0f,0.0f,0.0f),1));

osg::Geode* geode = new osg::Geode;
geode->setCullingActive(false);
geode->setStateSet( stateset );
geode->addDrawable(drawable);

osg::Transform* transform = new MoveEarthySkyWithEyePointTransform;
transform->setCullingActive(false);
transform->addChild(geode);

osg::ClearNode* clearNode = new osg::ClearNode;
//   clearNode->setRequiresClear(false);
clearNode->setCullCallback(new TexMatCallback(*tm));
clearNode->addChild(transform);

return clearNode;
}