Yeah dude, you're right, I'm using a "paraboloid" formula, I just know it by other name - "semi-esfera" (on my first language), and it still need some fixing up to look more nice.
// Top half
Ny = -r*cosf(PI2*(float)(y+1) / (float)yring);
radius = r*sinf(PI2* (float)(y+1) / (float)yring);
// Bottom half
Ny = r*sinf(PI2*(float)(y+1) / (float)yring);
radius = r*cosf(PI2*(float)(y+1) / (float)yring);