Shaders HLSL

[Mythios]

Would of use happen to know how to use shaders? I've been on other forums trying to get help but no one is replying or even bothering. I'm generating a sphere in 3D and want to be able to use a shader to layer 2 textures of it like this.

http://freespace.virgin.net/hugo.elias/models/p4_b.gif

I already have my sphere in the shape of the object, but I need to know how to use a shader to test for the height of each vertex from the center of the sphere, I'd gather. I'm just getting confused trying to do this - and it's more frustrating when you can't find anything on what I'm trying to do.

Thanks,
Myth.

[hamsterman]

Well, have you tried simply passing the center of the sphere into the shader with SetFloatArray and then write in the vertex shader if(/*pythagoras here*/ < water_level) /*tex1*/; else /*tex2*/? This wont give the sharp edges seen in the picture though... The picture looks as if there are two overlapping meshes.
Also, I haven't done anything with hlsl for a long time, so I cold be making no sense...