Added poly_tube(), an extruded poly_ring().

Added missing hinge image.

readme.md

@@ -4499,6 +4499,7 @@ The module provides `poly_circle()`, `poly_cylinder()` and `poly_ring()` that is
 | ```poly_circle(r, sides = 0)``` | Make a circle adjusted to print the correct size |
 | ```poly_cylinder(r, h, center = false, sides = 0)``` | Make a cylinder adjusted to print the correct size |
 | ```poly_ring(or, ir)``` | Make a 2D ring adjusted to have the correct internal radius |
+| ```poly_tube(or, ir, h, center = false)``` | Make a tube adjusted to have the correct internal radius |
 | ```slot(r, l, h = 100)``` | Make a horizontal slot suitable for CNC routing, set h = 0 for 2D version |
 
 ![polyholes](tests/png/polyholes.png)

tests/polyholes.scad

@@ -52,8 +52,8 @@ module polyholes() {
     sizes = [1.5, 2, 3, 4];
     for(i = [0 : len(sizes) - 1])
         translate([i * 10, -10]) {
-            color(pp1_colour) linear_extrude(height = 1)
-                poly_ring(ir = ir, or = cir + sizes[i] * extrusion_width);
+            color(pp1_colour)
+                poly_tube(ir = ir, or = cir + sizes[i] * extrusion_width, h = 1);
 
             rod(2 * ir, 3);
        }

utils/core/polyholes.scad

@@ -62,6 +62,10 @@ module poly_ring(or, ir) { //! Make a 2D ring adjusted to have the correct inter
                 }
 }
 
+module poly_tube(or, ir, h, center = false) //! Make a tube adjusted to have the correct internal radius
+    extrude_if(h, center)
+        poly_ring(or, ir);
+
 module drill(r, h = 100) //! Make a cylinder for drilling holes suitable for CNC routing, set h = 0 for circle
     extrude_if(h)
         circle(r = corrected_radius(r, r2sides(r)));