Unity Terrrain editor halves FPS on IOS?

Unity Engine
1

Hey, we are making a physics based 3D racing’ish game for IOS (target: 3GS+).

Resume:
Previously we made our maps as a 3D mesh with a single texture stretched out on it.
With the support of Terrain on IOS since summer, we wan’t to shift to that.
We have made a map, which was a replica of a map made “in the old way”. It functions on the Iphone and looks great visually.

Problem:
It looks great on Iphone, but it kills the framerate to like 50% of our old approach (10-15 compared to 25-30).
Our settings is mostly the lowest they go, regarding terrain “resolution”, “pixel errors” and “LOD”.
But we cant get above 10-15 FPS

We have even tried removing the texture, the props, the background (advanced skybox) and only have the white “terrain mesh” that we drive around in.
-which only give like +1-3 fps.

Is our script / physics / car-code colliding with the terrain-rendering-and-collision-detection in some way?
OR
Is the support for the terrain editor on IOS only “theoretically” as it gives really poor performance?

2

thats to expect, neithers are the shaders too light (you do realtime blending with a splat map and 4 textures and have many other things rendering in parallel too) nor will the heightmap handling and collision calculation against a heightmap ever be fast.
The terrain + foliage on it is already heavy enough on an Intel GMA900 and GMA950 and both have a major edge over the SGX535 in the 3GS, 4th gen and ipad1

The support is not theoretical, its there, but the devices generally just aren’t fast enough. try it with the iPad2 and iPhone 4S and use meshes or the Terrain4Mobile system for the rest

3

Notices the T-4-M also, is it any good?

Or do someone at least know some terrain shaders (splatmap or similar), that works on IOS without the same extreme performance loss?