   gltranslate and black screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glFrustum(left,right,bottom,top,0.9,2*diam + 2);glMatrixMode(GL_MODELVIEW); glLoadIdentity();GLfloat LightPosition1[]= { 0.0f, 0.0f, 0.0f, 1.0f };glLightfv(GL_LIGHT1, GL_POSITION,LightPosition1); //stick the light to the viewergluLookAt (0.0,0.0,m_modelsCompainer->getCenter()[2]+diam + 1,m_modelsCompainer->getCenter()[0],m_modelsCompainer->getCenter()[1],m_modelsCompainer->getCenter()[2],0.0, 1.0, 0.0);glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, colorVec);    glPushMatrix();glLoadIdentity();glTranslatef((GLfloat)0,(GLfloat)0,(GLfloat)1);//render the mesh hereglPopMatrix();Why I am getting black screen?when performing transformation in modelview mode,does the transformation is performed in local coordinate system of the object   