^
From what I member looking through it's the same as No-back-Culling or the two_sided standard 3dgs material.. **However, if you are picking up fps and can see on screen transparency disabled than Kartoffel is more likely correct.
It seems to set bool PASS_SOLID which is used in sc_lights.c
set(shadowView.material,PASS_SOLID);
set(shadowMtl,PASS_SOLID);
set(screen.views.sunShadowDepth[i].material,PASS_SOLID);
which seems to be a standard view material flag for 3dgs here
http://www.conitec.net/beta/material-flags.htmOpposite of TRANSLUCENT: enforces rendering on the solid pass, i.e. together with non-transparent objects. For entities with alpha channel textures that are used for other purposes, such as a height map in a shader. Entities in the solid pass are not sorted, and thus render faster than in the transparent pass. This flag can also be set by defining a bool variable within the .fx file (bool PASS_SOLID;) A
And PotatoMan saves the day Again... He's correct!!
Selective uses in object shaders may be to force that object alone into the solid pass.
I could also be a switch for alphatest or alphablend(???). Sorry I can't recall now, I may have know more in post past when we talked transparency before, if you can find those.. 
