Opacity: 0ff, Translucency: 0.8 (more of BackMtl)

Opacity: off, Translucency: 0.2 (more of FrontMtl)

Opacity: 0.5, Translucency: 0.8 (more of BackMtl)

Opacity: 0.5, Translucency: 0.2 (more of FrontMtl)

In every pyramid, there is a VRayLight (Sphere type), which are the only light sources in the scene.

The setup of the VRay2SidedMtl includes a VRayMtl in the Front Material slot, and Check-Box Off.

That means V-Ray will use the same material for the Back one as well.

The VRayMtl (Front material) has a diffese Bitmap, and for the opacity - a procedural Output map.