Shader that blends two textures according to vertex color

Graphics Shaders & Materials
1

I need a simple shader for iphone for the road.
It should blend two textures for example the main road and the rocks texture in this rule: if we have white in vertex color we should use first texture, if black - second. And if we have grey for example we should blend two textures in 50/50.
Also it would be great to use lightmap to 2d uv channel.
Anyone can help with this?

2

Moving to ShaderLab section.

3

sounds like the simple “alpha blend equation”

outCol = primCol * val + secCol * (1-val)

with val beeing the brightness (or just the red color component), primCol beeing the color on the first texture and sec col beeing the color on the second texture.

and you can’t use an additional texture unless you want 2 passes, because the iphone (earlier to 3GS) only supports 2 textures per pass (its a phone, not a pc)