was thinking of a lot of tiled textures, and wondered where and how multi texturing something impacts on performance?
well fro one experience i had with a game using it , with 4 channel + light map over it etc …well it hurt for sure ^^, in our case the shader was custom made, scene also was containing lot of particle stuff , fog, numerous model on screen etc…
well with all that app could get a 30 fps stable on 3gs ( for 3g many get cutter ) …with newest device you should be good , anyway you can use this without kill your app but you will have to sacrifice quite a bit of fps in the process eventually, unless you can get a super hyper magic custom made shader for this purpose that will lower the drop.
well now i am not expert multi texture on iOS , so this is just a feedback of what i seen already
oops some mess either with unity website or damn safari >> double post XD
Are you talking about multi texturing or multi layering?
The later means you draw texture on top of each other, the former means that different parts of a model are drawn with different textures.
The later generates 1 drawcall per material applied
The formers performance depends on what you do operation wise in the shader. can be relatively light but you can also totally kill the performance