Making Elbows with OpenSCAD

This thing is not so much a model to print as an example of an improved solution to the problem of joining two cylinders right angles.

The obvious way to do this would be to simply offset and rotate the two pipes and place a sphere at the joint with a sphere() function.

However, when coded this way the facets will not line up. You can see this in the model at the left and in the zoomed of boundary between the cylinders and the sphere. The code for that approach in the function elbow_sphere()

```
module elbow_sphere() {
sphere(1);

rotate([180,0,0]) cylinder(2,1,1);
rotate([-90,0,0]) cylinder(2,1,1);
}
```

The problem happens even if the $fn numbers are the same for the cylinder and the sphere function. Of course, you can increase $fn and make it less noticeable, but at the cost of a much more complex .stl file when you render it.

Alternatively, you can control how the facets are generated by using rotate_extrude() on a semi-circle and using that in p