Linear Extrude with Scale as an interpolated function

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OpenScad Linear Extrude extended use example. Module and function example to make the linear_extrude scaling functionality follow a function. It is a piecewise union of linear_extrudes. The example uses a sine function as a scaling function. Twisting by a Scalar is incorporated and can also be passed to the module. How I Designed This In my attempt to emulate a propeller blade with an aerofoil profile, I wanted to define a progressive increment and decrement of the blade width, maintaining the profile as it moves from root to tip of the blade. Main Code module linear_extrude_fs(height=1,isteps=20,twist=0,slices=0){ union(){ for(i = [ 0: 1: isteps-1]){ translate([0,0,i*height/isteps]) linear_extrude( height=height/isteps, twist=twist/isteps, scale=f_lefs((i+1)/isteps)/f_lefs(i/isteps), slices=slices) rotate([0,0,-(i/isteps)*twist]) scale(f_lefs(i/isteps)) obj2D_lefs(); } } } User must implement a function with the name function f_lefs(x) =...; which returns the value of the scale with an expected input ranging from 0 to 1 along the extruded height. User must also implement a module named module obj2D_lefs(){...} to define the 2 dimensional object to extrude. Example Scaling Functions In the example, I am using a sine function to define a "curved scaling factor". function f_lefs(x) = let(span=150,start=20,normpos=45) sin(x*span+start)/sin(normpos); The variable span defines how many degrees of a sine curve I use along my height extrusion. The variable start defines at what part of the sine curve my scaling starts. As my input is from 0 to 1, sin(x*span+start) with a span of 150 and start of 20, the scaling factor will follow a range from sin(20) to sin(170). The variable normpos allows me to define the degrees at which I normalize my function. In the case of the example, 45 degrees is my normalization point, leading to an initial scaling of sin(20)/sin(45) = 0.48, a maximum scaling at 90º = 1.414 and a final scaling of 0.245.