jogl - GL_LINES is not visible inside a cube -

what draw parallelepiped (using gl_quads) , edges (using gl_lines). parallelepiped supposed squash field, , camera inside it. problem when use gl_lines, line drawn not visible when camera inside parallelepiped.

couple of screenshots understand better :

inside - line not visible : http://i.stack.imgur.com/ozky5.png

outside - line visible : http://i.stack.imgur.com/ah40o.png

this what's inside init method :

gl2 gl = drawable.getgl().getgl2();      // opengl graphics context       glu = new glu();                         // gl utilities       gl.glclearcolor(0.0f, 0.0f, 0.0f, 0.0f); // set background (clear) color       gl.glcleardepth(1.0f);      // set clear depth value farthest       gl.glenable(gl_depth_test); // enables depth testing       gl.glenable(gl_blend);       gl.glblendfunc(gl_src_alpha, gl_one_minus_src_alpha);       gl.gldepthfunc(gl_lequal);  // type of depth test       gl.glhint(gl_perspective_correction_hint, gl_nicest); // best perspective correction       gl.glshademodel(gl_smooth); // blends colors nicely, , smoothes out lighting       gl.glenable(gl_line_smooth); 

and display method :

gl2 gl = drawable.getgl().getgl2();  // opengl 2 graphics context   gl.glclearcolor(0.55f, 0.55f, 0.55f, 1.0f);   gl.glclear(gl_color_buffer_bit | gl_depth_buffer_bit); // clear color , depth buffers   gl.glloadidentity();  // reset model-view matrix     gl.gltranslated(-3.2, -2.82, -10); // translate screen    gl.glbegin(gl_quads); // start drawing quad   gl.glcolor4ub(r,g,b, alpha);    gl.glvertex3d(0, 0, 0);   gl.glvertex3d(0, 5.640, 0);   gl.glvertex3d(6.400, 5.640, 0);   gl.glvertex3d(6.400, 0, 0);    gl.glvertex3d(0, 0, 0);   gl.glvertex3d(0, 5.640, 0);   gl.glvertex3d(0, 5.640, 9.750);   gl.glvertex3d(0, 0, 9.750);    gl.glvertex3d(6.400, 0, 0);   gl.glvertex3d(6.400, 5.640, 0);   gl.glvertex3d(6.400, 5.640, 9.750);   gl.glvertex3d(6.400, 0, 9.750);    gl.glvertex3d(0, 0, 9.750);   gl.glvertex3d(0, 5.640, 9.750);   gl.glvertex3d(6.400, 5.640, 9.750);   gl.glvertex3d(6.400, 0, 9.750);    gl.glvertex3d(0, 0, 0);   gl.glvertex3d(0, 0, 9.750);   gl.glvertex3d(6.400, 0, 9.750);   gl.glvertex3d(6.400, 0, 0);    gl.glvertex3d(0, 5.640, 0);   gl.glvertex3d(0, 5.640, 9.750);   gl.glvertex3d(6.400, 5.640, 9.750);   gl.glvertex3d(6.400, 5.640, 0);    gl.glend(); // done drawing quad    gl.gllinewidth(2);   gl.glbegin(gl_lines);   gl.glcolor4ub((byte)0,(byte)0,(byte)0, (byte)255);    gl.glvertex3d(0, 0, 0);   gl.glvertex3d(0, 5.640, 0);    gl.glend(); 

thank help.

lines draw using same z-buffer quads. when outside, lines closer camera edges of quads , draw. when inside, surface of quads closer , line not draw. because of numerical errors lines can appear or disappear time time. turn of depth test , lines should draw.