Linear Extrude with Twist and Scale as interpolated functions

thingiverse

OpenScad Linear_Extrude extended use example. Module and function example to make the linear_extrude scaling and twisting functionality to follow a function. It is a piecewise union of linear_extrudes. The example uses a sine function as a scaling and twist function. How I Designed This Motivation: In an 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 moving from root to tip of the blade. Main Code module linear_extrude_ftfs(height=1,isteps=20,slices=0){ union(){ for(i=[0:1:isteps-1]){ translate([0,0,i*height/isteps]) linear_extrude( height=height/isteps ,twist=leftfs_ftw((i+1)/isteps)-leftfs_ftw(i/isteps) ,scale=leftfs_fsc((i+1)/isteps)/leftfs_fsc(i/isteps) ,slices=slices ) rotate([0,0,-leftfs_ftw(i/isteps)]) scale(leftfs_fsc(i/isteps)) obj2D_leftfs(); } } } User must implement functions with the names function leftfs_fsc(x) =...; and function leftfs_ftw(x) =...; which returns the value of the scale and twist respectively with an expected input ranging from 0 to 1 along the extruded height. User must also implement a module named module obj2D_leftfs(){...} to define the 2 dimensional object to extrude. Constant Scaling and Twist Functions For a Constant Scaling Function use: function leftfs_fsc(x) = let(scale=0.5) 1-x*(1-scale); For a Constant Twisting Function use: function leftfs_ftw(x) = let(twist=90) twist*x;