smoothed out the corners between catears and headband

scad/base/smoothing.scad

@@ -0,0 +1,18 @@
+//smoothing smooths a corner, spanned by v1, v2 and v3 with radius r
+module smoothing(v1, v2, v3, r, th = 0){
+  n1 = (v1-v2)/norm(v1-v2);
+  n2 = (v3-v2)/norm(v3-v2);
+  alpha = acos(n1*n2)/2;
+  n3 = (n1+n2)/norm(n1+n2);  
+    
+  centre = v2+n3*(r/sin(alpha));
+  l = r*sqrt((1/sin(alpha)^2)-1);
+
+  translate(th*n3){
+    difference(){
+      polygon([v2+l*n1,v2,v2+l*n2]);
+      translate(centre)
+        circle(r = r, $fn = 64);  
+    }
+  }  
+}

scad/catears.scad

@@ -1,14 +1,16 @@
 use <base/bezier_extrusion.scad>;
 use <base/headband.scad>;
+use <base/smoothing.scad>;
 
 thickness = 2.7;
 height = 5.5;
 epsilon = 0.001; //needs to be small but greater 0 so that the model doesn't break
+smoothing = true;
 
 module catear(){
 
   ctrl_ear1 = [[49,96],[58,112],[63,137],[61.5,141]];
-  ctrl_ear2 = [[61.5+1.5*epsilon,141-4*epsilon],[60,145],[42.5,140.5],[18,123]];
+  ctrl_ear2 = [[61.5+1.5*epsilon,141-4*epsilon],[60,145],[42.5,140.5],[18,123]];      
 
   shape_band = [[thickness/2,height/2-0.4],
                 [thickness/2,-height/2+0.4],
@@ -21,6 +23,34 @@ module catear(){
     
   bezier_extrude(ctrl = ctrl_ear1, shape = shape_band, sections = 32);
   bezier_extrude(ctrl = ctrl_ear2, shape = shape_band, sections = 32);
+    
+  //smoothing the corners between ears and headband
+  if(smoothing){
+    
+    //these values are approximations to intersections and tangents  
+    c1 = [18.3,123.21];
+    v1 = [18.33,123.2];
+    v2 = [18.35,123.25];
+    v3 = [18.27,123.22];
+    
+    c2 = [48.75,95.56];
+    v4 = [48.85,95.35];
+    v5 = [49,96];
+    v6 = [48.65,95.8];  
+  
+    k = 4; //pick k such that 0.4/k < layer height
+      
+    for(i = [0 : k]){  
+      linear_extrude(height-i*0.8/k, center = true, convexity = 10){  
+        smoothing(v1,c1,v2,r=2.5,th=thickness/2-(k-i)*0.4/k);
+        smoothing(v2,c1,v3,r=4,th=thickness/2-(k-i)*0.4/k);
+        smoothing(v4,c2,v5,r=4,th=thickness/2-(k-i)*0.4/k);
+        smoothing(v5,c2,v6,r=2.5,th=thickness/2-(k-i)*0.4/k);  
+      }
+    }
+    
+  }  
+  
 }
 
 module catears(){