source: GTP/trunk/App/Demos/Illum/IBRBillboardCloudTrees/OGRE/IBRTreesOGRE/media/materials/programs/Example_Fresnel.cg @ 1493

// Vertex program for fresnel reflections / refractions
void main_vp(
                float4 pos                      : POSITION,
                float4 normal           : NORMAL,
                float2 tex                      : TEXCOORD0,
                
                out float4 oPos         : POSITION,
                out float fresnel   : COLOR,
                out float3 noiseCoord : TEXCOORD0,
                out float4 projectionCoord : TEXCOORD1,

                uniform float4x4 worldViewProjMatrix,
                uniform float3 eyePosition, // object space
                uniform float fresnelBias,
                uniform float fresnelScale,
                uniform float fresnelPower,
                uniform float timeVal,
                uniform float scale,  // the amount to scale the noise texture by
                uniform float scroll, // the amount by which to scroll the noise
                uniform float noise  // the noise perturb as a factor of the  time
                )
{
        oPos = mul(worldViewProjMatrix, pos);
        // Projective texture coordinates, adjust for mapping
        float4x4 scalemat = float4x4(0.5,   0,   0, 0.5, 
                                       0,-0.5,   0, 0.5,
                                                                   0,   0, 0.5, 0.5,
                                                                   0,   0,   0,   1);
        projectionCoord = mul(scalemat, oPos);
        // Noise map coords
        noiseCoord.xy = (tex + (timeVal * scroll)) * scale;
        noiseCoord.z = noise * timeVal;

        // calc fresnel factor (reflection coefficient)
        float3 eyeDir = normalize(pos.xyz - eyePosition);
        fresnel = fresnelBias + fresnelScale * pow(1 + dot(eyeDir, normal), fresnelPower);
        
}

// Fragment program for distorting a texture using a 3D noise texture
void main_fp(
                float fresnel                           : COLOR,
                float3 noiseCoord                       : TEXCOORD0,
                float4 projectionCoord          : TEXCOORD1,
                
                out float4 col          : COLOR,
                
                uniform float distortionRange,
                uniform float4 tintColour,
                uniform sampler3D noiseMap,
                uniform sampler2D reflectMap,
                uniform sampler2D refractMap
                )
{
        // Randomly chosen offset for y noise sample
        float3 yoffset = float3(0.31, 0.58, 0.23);
        float2 distort;
        // Sample the noise texture at 2 places
        distort.x = tex3D(noiseMap, noiseCoord).x;
        distort.y = tex3D(noiseMap, noiseCoord + yoffset).x;
        // Scale the distortion from [0,1] to [-range,range]
        distort = (distort * 2 - 1) * distortionRange;

        // Do the tex projection manually so we can distort _after_
        float2 final = projectionCoord.xy / projectionCoord.w;
        final += distort;
        
        float4 reflectionColour = tex2D(reflectMap, final);
        float4 refractionColour = tex2D(refractMap, final) + tintColour;
        col = lerp(refractionColour, reflectionColour, fresnel);


}