Rendering to texture hides the front face,something's wrong with the z buffer?

Question

I want to render my scene to a texture and apply a blur shader to this texture .The problem is that when I draw back my texture the front faces of the cubes are invisible

without supersampling

with supersampling

*Ignore the opaque thing around the cube in both photos.I double render the cube once with less alpha and more scale ,I disabled this but I have the same problem.

For some reason I am using the y as z and z as y,so the front face of the cube has less y than the back face(instead of z) ,I am guessing something is wrong with the z-buffer.

The render to texture code:

public class RenderOnTexture {
    private float m_fboScaler = 1f;
    private boolean m_fboEnabled = true;
    private FrameBuffer m_fbo = null;
    private TextureRegion m_fboRegion = null;
    public RenderOnTexture(float scale) {
        int width = (int) (Gdx.graphics.getWidth()*scale);
        int height = (int) (Gdx.graphics.getHeight()*scale);
        m_fbo = new FrameBuffer(Format.RGB565, (int)(width * m_fboScaler), (int)(height * m_fboScaler), false);
        m_fboRegion = new TextureRegion(m_fbo.getColorBufferTexture());
        m_fboRegion.flip(false,false);
    }
    public void begin(){
        if(m_fboEnabled)
        {                  
            m_fbo.begin();
            Gdx.gl.glClearColor(0, 0,0,0);
            Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        }
    }
    public TextureRegion end(){
        if(m_fbo != null)
        {
            m_fbo.end();
            return m_fboRegion;
        }  
        return null;
    }
}

Answer 1

The Boolean argument in the FrameBuffer enables a depth buffer attachment. And the depth buffer must be cleared along with the color buffer.