void Corrdinate_spacesApp::update()
{
    vector<Vec3f> positions;
    positions.resize(4);
    for( int i=0;i<positions.size();i++ ){
        
        Perlin p;
        positions[i] = 3. * ( p.dnoise( getElapsedSeconds()+i,
                                       getElapsedSeconds()+i*2,
                                       getElapsedSeconds() ) * 2 - Vec3f(1.,1.,1.) );
        
    }
    
    mVboMesh->bufferPositions(positions);
    mVboMesh->unbindBuffers();
}