Transparent objects in OpenGl ES 2.0

Question

So I've been playing around with OpenGL ES 2.0 on Android but now got to a problem I haven't been able to solve. Apologies in advance, it appears that I'm not allowed to post more that two links (yet), so I put my three images in a Photobucket album here.

I'm trying to create a 3D environment that is enclosed by transparent areas ("colored glass"). To see if it works I also put a opaque cube within. I enabled the following capabilities:

GLES20.glEnable(GLES20.GL_CULL_FACE);
GLES20.glEnable(GLES20.GL_DEPTH_TEST);
GLES20.glEnable(GLES20.GL_BLEND);
GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA);

Now the picture looks like this (screenshot 1). Not bad, but not exactly how I wanted it: A (lower) wall at the back as well as the wall on the right should be visible because the wall I'm looking through is transparent.

Then I found that and tried using GLES20.glDepthMask(true); before drawing the opaque and GLES20.glDepthMask(false); before drawing the transparent objects, as well as disabling blending while drawing the opaque objects.

The result (screenshot 2) looks quite messed up. But then I had another idea, not to turn off writing to the depth buffer but to turn off GLES20.DEPTH_TEST altogether, while drawing the transparent objects.

That (screenshot 3) got me closest tho the picture I'm looking for. You can finally see the backwall as well as the right sidewall but, because the depth testing is disabled when drawing the opaques, the cube is partially covered by the backwall, which it shouldn't be.

Does anyone know how to get the effect I'm looking for?

Answer 1

I think that I solved it. By that I mean that it works in my case but I can't tell if that is just by coincidence...

I am enabling depth testing and blending as usual. Then, when drawing, I draw the opaque shapes first and the transparent shapes second, like before. But, while drawing the transparent shapes, I turn GLES20.glDepthMask(..) off to not write to the depth buffer and thus draw all transparent shapes that are not covered by opaque shapes. I did that previously (picture 2) and it completely messed up but I now I do it in reverse - disabling the depth mask for transparent shapes, not opaque ones.