Are normal maps limited?

[marscaleb]

While I was poking around inside the Citadel demo today, I switched to detail lighting and noticed that very few materials have normal maps; most just use diffuse maps with shadows drawn on them like back in the day.

This has led me to be worried. Is there a pressing limit for how many materials or actors I can use in a scene that have normal maps?
Or was this decision made just to reduce the cost of memory?

[Curious]

While I was poking around inside the Citadel demo today, I switched to detail lighting and noticed that very few materials have normal maps; most just use diffuse maps with shadows drawn on them like back in the day.

This has led me to be worried. Is there a pressing limit for how many materials or actors I can use in a scene that have normal maps?
Or was this decision made just to reduce the cost of memory?

Mobile Normal Texture - Sets a normal map texture for this material and enables per-pixel shading features. A normal map texture may be required for other material features, such as per-pixel specular. Setting a normal map texture may significantly impact the shading performance of the material.

From the UDN.

Regarding mobile development - if you can get away by faking it - fake it.

[marscaleb]

Sure, I can buy that as a general rule of thumb, but "impact the shading performance of the material" can be interpreted in a few ways.
I mean, if you have a material with no normal map, you are NOT going to get much of a performance out of the shader.
It doesn't clearly state that having a normal map will drop the performance of the engine, it says it will drop the performance of the material. That sounds to me like its saying the obvious "You need to have this if you want the other stuff" not the obvious "You should reduce how many normal maps you have to reduce your memory."
Hence why I am looking for a clearer answer.

[marscaleb]

Seriously though, I don't have an answer here.
Is this just about reducing the memory costs for the game, or do normal maps actually present a noticeable loss of gameplay performance?

[ffejnosliw]

Anything that increases the complexity of a material is bound to make it slower to render. How much that actually affects the game depends on the use of the material in the world. Is it used once on a tiny surface that doesn't take up much screen space? That probably won't be too much of an impact. Is it a wall material used everywhere that takes up a significant amount of the screen at all times? That is probably going to be noticeable.