ofEnableDepthTest with ofGLProgrammableRenderer

Hello,

I am using 6 outer surfaces of a NURBS volume to create a volumetric view.
Using the default renderer and ofEnableDepthTest() Invisible lines are not drawn as expected.
However if I switch to ofGLProgrammableRenderer, ofEnableDepthTest has no effect.

I am using VS2012 on Windows 8.1

As an OpenGL beginner I was wondering if there were any other steps to make ofEnableDepthTest and ofGLProgrammableRenderer work.
Any advice is appreciated.

Thanks.

can you post some images? depth testing is activated with the same call using the programmable renderer so it might be something else. are you drawing using alpha?

As a new user I cannot upload images so please forgive the links.

With default renderer : http://i41.tinypic.com/3585ndk.png
With programmable renderer : http://i39.tinypic.com/2ik5ush.png

The only difference in two images is the code :
ofSetCurrentRenderer(ofGLProgrammableRenderer::TYPE);

The shape is composed of six ofmeshes and a series of ofCircle meshes.
Colors are set using predefined ofColors ie ofColor::darkBlue;

Other than ofEnableDepthTest(); I don’t apply any other settings.