#define M(row,col) m[col * 4 + row]

void Transform_Point(double out[4], const double m[16], const double in[4]){

out[0] = M(0, 0) * in[0] + M(0, 1) * in[1] + M(0, 2) * in[2] + M(0, 3) * in[3];

out[1] = M(1, 0) * in[0] + M(1, 1) * in[1] + M(1, 2) * in[2] + M(1, 3) * in[3];

out[2] = M(2, 0) * in[0] + M(2, 1) * in[1] + M(2, 2) * in[2] + M(2, 3) * in[3];

out[3] = M(3, 0) * in[0] + M(3, 1) * in[1] + M(3, 2) * in[2] + M(3, 3) * in[3];

}

osg::Vec3d WorldToScreen(osgViewer::View* view,osg::Vec3 worldpoint){

double in[4], out[4];

in[0] = worldpoint._v[0];

in[1] = worldpoint._v[1];

in[2] = worldpoint._v[2];

in[3] = 1.0;

//獲得當前的投影矩陣和模型檢視矩陣

osg::Matrix projectMatrix= view->getCamera()->getProjectionMatrix();

osg::Matrix viewprojectMatrix = view->getCamera()->getViewMatrix();

//下面計算 模型檢視矩陣 * 投影矩陣 * 視口視窗變換矩陣

double modelViewMatrix[16];

memcpy(modelViewMatrix,viewprojectMatrix.ptr(),sizeof(GLdouble) * 16);

Transform_Point(out, modelViewMatrix, in);

double myprojectMatrix[16];

memcpy(myprojectMatrix,projectMatrix.ptr(),sizeof(GLdouble) * 16);

Transform_Point(in, myprojectMatrix, out);

if(int(in[3] * 100000) == 0){

return osg::Vec3d(0,0,0);

}

in[0] /= in[3];

in[1] /= in[3];

in[2] /= in[3];

int viewPort[4];

osg::Viewport* myviewPort = view->getCamera()->getViewport();

viewPort[0] = 0;

viewPort[1] = 0;

viewPort[2] = mConfigure->GetScreenWidthPixel(); //橫向象素點

viewPort[3] = mConfigure->GetScreenHeightPixel();//縱向象素點

//計算 三維點在螢幕上的二維投影點

osg::Vec3d sceenPoint;

sceenPoint._v[0] = (int)(viewPort[0] + (1 + in[0]) * viewPort[2] / 2 + 0.5);

sceenPoint._v[1] = (int)(viewPort[1] + (1 + in[1]) * viewPort[3] / 2 + 0.5);

sceenPoint._v[2] = 0;

return sceenPoint;

}