Hi Elang,

re:
> That's very close to what I'm trying to achieve, expect for it to become a relief, the 'back part' of the
> model should be flat and aligned to the origin axis like so:

I don't think it's possible to achieve that just using a perspective projective matrix transformation as is being done here.

To produce geometry like you're describing I think that after the perspective projection you would need to generate silhouette curves and then extrude those silhouettes down to the base plane, like described here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=10568.6

It's probably better to do it using a depth map rendering + height field approach or zbrush where there are specific tools for it.

- Michael