source: downloads/ogreode/demos/Media/autoterraintexture.cg @ 30

// Vertex program for automatic terrain texture generation
void main_vp
(
    float4             iPosition           : POSITION,
        float4             iNormal             : NORMAL,
        float2             iTexcoord           : TEXCOORD0,

        out float4         oPosition           : POSITION,
        out float4         oTexcoord           : TEXCOORD0,
        out float4         oColor0             : COLOR0,
        out float4         oColor1             : COLOR1,
        out float4         oFog                : TEXCOORD1,

        uniform float4x4   worldViewProj,
        uniform float4     lightDirection,
        uniform float4     ambientLight,

        uniform float4     configSettings,
        uniform float4     fogSettings,
        uniform float4     fogColour
)
{
    // Calculate the output position and texture coordinates
        oPosition  = mul(worldViewProj,iPosition);
    oTexcoord = float4(iPosition.x,iPosition.z,0.0,0.0) * configSettings[0];

    float fog = clamp(( oPosition.z - fogSettings[0] ) / (fogSettings[1] - fogSettings[0]),0.0,1.0) * fogSettings[2];

    // Calculate the diffuse and the ambient lighting
    float diffuse = dot(iNormal,lightDirection);

    // Set the output color based on the lighting
    float rock_factor = (iNormal.y > configSettings[1])?0.0:(clamp((configSettings[1] - iNormal.y) * configSettings[2],0.0,1.0));
    float4 color = float4(diffuse,diffuse,diffuse,1.0) + (ambientLight * configSettings[3]);
    oColor0 = (1.0 - fog) * (color * (1.0 - rock_factor));
    oColor1 = (1.0 - fog) * (color * rock_factor);
    oFog = fogColour * fog;
}

// Fragment program for automatic terrain texture generation
void main_fp
(
    float4              iTexcoord       : TEXCOORD0,
    float4              iColor0     : COLOR0,
    float4              iColor1     : COLOR1,
    float4              iFog        : TEXCOORD1,

        out float4          oColor              : COLOR,

    uniform sampler2D   textureUnit0,
    uniform sampler2D   textureUnit1
)
{
    // Sample the texture to get the output colour, times the lighting
        oColor = iFog + (tex2D(textureUnit0,iTexcoord.xy) * iColor0) + (tex2D(textureUnit1,iTexcoord.xy) * iColor1);
        oColor.a = 1.0;
}