kernel Glass
<
    nameSpace: "f4f::Shaders";
    vendor: "Manuel Bua";
    version: 1;
    description: "Displace original pixels to simulate a glassy look-through";
>
{
    parameter float displaceIntensity
    <
        minValue:       1.;
        maxValue:       100.;
        defaultValue:   30.;
    >;

    parameter float offsetX
    <
        minValue:       -1.;
        maxValue:       1.;
        defaultValue:   0.;
    >;

    parameter float offsetY
    <
        minValue:       -1.;
        maxValue:       1.;
        defaultValue:   0.;
    >;

    parameter float offsetScale
    <
        minValue:       1.;
        maxValue:       200.;
        defaultValue:   100.;
    >;

    parameter float displaceScale
    <
        minValue:       .1;
        maxValue:       2.;
        defaultValue:   .4;
    >;
    
    void evaluatePixel( in image4 img1, in image4 img2, out pixel4 result )
    {
        float2 pos = outCoord();
        float2 srcPos = pos;
        srcPos.x += offsetX * offsetScale;
        srcPos.y += offsetY * offsetScale;
        float4 normal = 2. * ( sampleLinear( img2, pos * displaceScale ) - .5 );
        pixel4 res = sampleLinear( img1, srcPos + ( normal.xy * displaceIntensity ) );
        res.a = normal.z;
        result = res;// + sampleLinear( img1, srcPos + ( normal.xy * displaceIntensity ) ) * .4;
    }
}