**Dear forum**

A 2-sided glossy alpha shader. Does this exist, or does it have to be made up? ? if so maybe one of you can give me a hint on how to do it.

Thanks

**Carl Emil**

**Dear forum**

A 2-sided glossy alpha shader. Does this exist, or does it have to be made up? ? if so maybe one of you can give me a hint on how to do it.

Thanks

**Carl Emil**

The most efficient way of doing 2-sided *anything* shaders is to do it in your 3D app: duplicate all faces flip the normals to get the backfacing…

But if you really really want a 2-sided alpha glossy shader, duplicate the alpha glossy one and put “Cull Off” in it, and call it something different.

–Eric

Effecient ? meaning prosessor friendly or easy to do?

Sounds easy.

Thanks

Carl Emil

Easy to do, and you get correct lighting on both sides of polygons, which you don’t get with “Cull Off”. Adding more polygons that way is unlikely to have any noticeable effect on the framerate, any more than turning off culling does anyway.

–Eric

Can you quantify the savings of duplicating the polygons over using two-sided materials? Are there any special cases where the two-sided material would be more efficient?

Not duplicating vertices/faces obviously uses less memory; also it’s potentially lower vertex transformation cost. The downside of just using Cull Off is that you get wrong lighting on the “back” side, because the normals are pointing into opposite direction.