shader
corrugations(
    float s = 0 
        [[
        int lockgeom = 0
        ]],
    float t = 0 
        [[
        int lockgeom = 0
        ]],
    float freq = 40,
    float ampl = 1,
    output float resultF = 0)
{
resultF = sin(s * M_PI * 2 * freq);
}