Two sided materials

[UgoUgo]

I've been wondering this for quite some time now.

What's the difference between the one-sided material and two-sided material other than the two-sided material shows two side of face... obviously.

Say if I use 100 footman, each of them using one-sided material in a map and another hundred using two-sided in another map, will it cause any significant difference in game performance between those two?

I saw that wc3 models never used two-sided materials unless it's necessary... so Im guessing it has quite a role with model efficiency or something.

I'd like to know more about this. Thanks.

 

[NhazUl]

It basically doubles the polycount. So yeah, WC3 models use mostly one-sided faces for precisely that reason: to be lighter on the engine. Two-sided materials are only used for when the two sides of a plane will be shown, like transparent or tralslucent surfaces.

 

[UgoUgo]

I see. This will certainly clear my doubts.

Another question, does having a lot of geosets in a model affect its efficiency? I know that some model have a lot of geoset due to using a lot of textures.

But let's ignore that first. A model with 10 geosets and another with 2 geoset. Which one is better or both have no difference?

Thanks again.

 

[Talavaj]

It is called backface culling, it is like so generally because back faces are usually inside the mesh and can't ever be seen hence require no rendering.

Even if you want a double sided material just duplicate the polygon and invert its normals and leave it one sided.
Backface culling OFF (or double sided) should never really been used ever.

Also, it is not much about the geosets as it is about the material, more materials means more draw-calls. So if each of the geosets has a different material it is going to perform worse than the one with less of them.

 

[GhostWolf]

Why would you prefer duplicating mesh data over disabling face culling? that makes no sense.

 

[Talavaj]

Why would you prefer duplicating mesh data over disabling face culling? that makes no sense.

Because of a million reasons ?
Because double sided material still has only one set of normals making the shading on the back side completely-messed up ?
Because back face culling off on an entire material is a complete waste of performance when you want only a tiny bit of it to be two sided ?
Because you can apply different materials on different sides.
Because most modern surface shaders and light calculating shaders don't work well on the back faces ?

 

[GhostWolf]

You are correct. Odd, I remembered that the driver generated the opposite normals (I didn't think about the other points either, shows the difference between an artist and a programmer, huh?).

 

[Talavaj]

yeah, things like that will get scorched into your mind when you spend time making stuff only to find your effort ruined because of how things look in real-time.