Takes a 2D polygon as input and extends it onto a sphere. If you light up a lamp on the north pole of the sphere, the shadow will return to the original 2D polygon. For more information, take a look at Stereographic projection.
The 2D polygon should center at the origin and you have to determine the side length of a square which can cover the 2D polygon. Because the 2D polygon will be extended onto a sphere, you can use
$fn to controll the sphere resolution.
shadow_side_leng: The side length of a square which can cover the 2D polygon.
$fn: Check the sphere module for more details.
use <stereographic_extrude.scad>; dimension = 100; render() stereographic_extrude(shadow_side_leng = dimension) text( "M", size = dimension, valign = "center", halign = "center" ); color("black") text( "M", size = dimension, valign = "center", halign = "center" );
For more advanced examples, take a look at my stereographic_projection collection.