public PerspectiveCamera cam = new PerspectiveCamera(80, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
public FrameBuffer FBO;
public TextureRegion fboRegion;
public ModelBatch modelBatch;
public SpriteBatch spriteBatch;

create(){
    FBO = new FrameBuffer(Format.RGBA4444,Gdx.graphics.getWidth(),Gdx.graphics.getHeight(),false);
    fboRegion = new TextureRegion(FBO.getColorBufferTexture());
    fboRegion.flip(false, true);
}

render(){
gl.glViewport(0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
gl.glClearColor(0, 0.5f, 0.9f, 1);
gl.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);

cam.update();

    FBO.begin();
    modelBatch.begin(cam);
        modelBatch.render(modelInstance1, environment);
        modelBatch.render(modelInstance2, environment);
    modelBatch.end();
    FBO.end();

    spriteBatch.begin();
        fboRegion.setTexture(FBO.getColorBufferTexture());
        spriteBatch.draw(fboRegion, 0, 0);
    spriteBatch.end();

}