[Radiance-general] Rectangular perforations

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Hello group!

I once found a cal file from Georg Mischler for circular perforations.
Now I wondered how to create rectangular perforations in a similar way.
Who has an idea (Georg?).

Iebele

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{
        perforate.cal
        Perforation function for approximately horizontal sufaces,
        for use in a mixfunc. Foreground is solid, background the holes.
        Set background to empty for a true perforation, or to a
different
        material for polka dots.

        Relative hole size is determined by A1.
    Size of single circle is 1 - scale as required (eg. 0.05m).

        x_hole cuts holes in x-direction (through the y-z plane)
        y_hole cuts holes in y-direction (through the x-z plane)
        z_hole cuts holes in z-direction (through the x-y plane)

    Georg Mischler 30. 04. 1993
}

`xn = mod(Px, 1) - 0.5;
`yn = mod(Py, 1) - 0.5;
`zn = mod(Pz, 1) - 0.5;

`outofcirc(x, y, r) = if(sqrt(x*x + y*y) - r, 1, 0);

z_hole = `outofcirc(`xn, `yn, A1);
x_hole = `outofcirc(`yn, `zn, A1);
y_hole = `outofcirc(`zn, `xn, A1);