riiis3.scad

function tangent_center(x0, x1, y0, y1, radius, otherside) =
  let(tmpnx = (y1 - y0),
      tmpny = -(x1 - x0),
      l = sqrt(tmpnx*tmpnx+tmpny*tmpny)*(otherside ? -1 : 1),
      nx = tmpnx/l,
      ny = tmpny/l,
      x3 = x0 + radius*nx,
      y3 = y0 + radius*ny,
      x4 = x1 + radius*nx,
      y4 = y1 + radius*ny,
      tmpvx = (x4 - x3),
      tmpvy = (y4 - y3),
      tmpv = sqrt(tmpvx*tmpvx+tmpvy*tmpvy),
      vx = tmpvx/tmpv,
      vy = tmpvy/tmpv,
      del = (-radius-y3)/vy,
      x2 = x3 + del*vx,
      y2 = y3 + del*vy)
  [x2,y2];


$fa = 8; $fs = 0.1;
x0 = 35;
y0 = 0;
x1 = 40;
y1 = -50;
radius = 4;

square(size=[100, 5], center=false);
polygon(points=[[x0, y0], [x1, y1], [x1+5, y1], [x0+5+2*(x1-x0), 0]]);

circ_center = tangent_center(x0,x1,y0,y1,radius,false);
#difference() {
  translate(circ_center) circle(r=radius);
  translate(circ_center) circle(r=radius-0.1);
}
echo(circ_center[0]);
echo(circ_center[1]);