Here we convert a 30 deg angle into an anchor using [cylindrical_to_xyz()](https://github.com/BelfrySCAD/BOSL2/wiki/coords.scad#function-cylindrical_to_xyz)
For Spherical type attachables, you can pass a vector that points at any arbitrary place on
the surface of the sphere:
```openscad-3D
include <BOSL2/std.scad>
sphere(r=50, anchor=TOP);
```
```openscad-3D
include <BOSL2/std.scad>
sphere(r=50, anchor=TOP+FRONT);
```
Here the [spherical_to_xyz()](https://github.com/BelfrySCAD/BOSL2/wiki/coords.scad#function-spherical_to_xyz) function converts spherical coordinates into
a vector you can use as an anchor:
```openscad-3D
include <BOSL2/std.scad>
sphere(r=50, anchor=spherical_to_xyz(1,-30,60));
```
---
Some attachable shapes may provide specific named anchors for shape-specific anchoring. These
will be given as strings and will be specific to that type of
attachable. When named anchors are supported, they are listed in a
"Named Anchors" section of the documentation for the module. The
`teardrop()` attachable, for example, has a named anchor called "cap" and in 2D the
`star()` attachable has anchors labeled by tip number:
```openscad-3D
include <BOSL2/std.scad>
teardrop(d=100, l=20, anchor="cap");
```
```openscad-2D
include <BOSL2/std.scad>
star(n=7, od=30, id=20, anchor="tip2");
```
---
Some shapes, for backwards compatibility reasons, can take a `center=` argument. This just
overrides the `anchor=` argument. A `center=true` argument is the same as `anchor=CENTER`.
A `center=false` argument chooses the anchor to match the behavior of
the builtin version: for a cube it is the same as `anchor=[-1,-1,-1]` but for a
cylinder, it is the same as `anchor=BOTTOM`.
```openscad-3D
include <BOSL2/std.scad>
cube([50,40,30],center=true);
```
```openscad-3D
include <BOSL2/std.scad>
cube([50,40,30],center=false);
```
---
Most 2D shapes provided by BOSL2 are also anchorable. The built-in `square()` and `circle()`
modules have been overridden to make them attachable.. The `anchor=` options for 2D
shapes treat 2D vectors as expected. Special handling occurs with 3D
vectors: if the Y coordinate is zero and the Z coordinate is nonzero,
then the Z coordinate is used to replace the Y coordinate. This is
done so that you can use the TOP and BOTTOM names as anchor for 2D
shapes.
```openscad-2D
include <BOSL2/std.scad>
square([40,30], anchor=BACK+LEFT);
```
```openscad-2D
include <BOSL2/std.scad>
circle(d=50, anchor=BACK);
```
```openscad-2D
include <BOSL2/std.scad>
hexagon(d=50, anchor=LEFT);
```
```openscad-2D
include <BOSL2/std.scad>
ellipse(d=[50,30], anchor=FRONT);
This final 2D example shows using the 3D anchor, TOP, with a 2D
object. Also notice how the pentagon anchors to its most extreme point on
the Y+ axis.
```openscad-2D
include <BOSL2/std.scad>
pentagon(d=50, anchor=TOP);
```
## Spin
You can spin attachable objects around the origin using the `spin=`
argument. The spin applies **after** anchoring, so depending on how
you anchor an object, its spin may not be about its center. This
means that spin can have an effect even on rotationally symmetric
objects like spheres and cylinders. You specify the spin in degrees.
A positive number will result in a counter-clockwise spin around the Z
axis (as seen from above), and a negative number will make a clockwise
spin:
```openscad-3D
include <BOSL2/std.scad>
cube([20,20,40], center=true, spin=45);
```
This example shows a cylinder which has been anchored at its FRONT,
with a rotated copy in gray. The rotation is performed around the
origin, but the cylinder is off the origin, so the rotation **does**
have an effect on the cylinder, even though the cylinder has
rotational symmetry.
```openscad-3D
include <BOSL2/std.scad>
cylinder(h=40,d=20,anchor=FRONT+BOT);
%cylinder(h=40.2,d=20,anchor=FRONT+BOT,spin=40);
```
You can also apply spin to 2D shapes from BOSL2, though only by scalar angle:
```openscad-2D
include <BOSL2/std.scad>
square([40,30], spin=30);
```
```openscad-2D
include <BOSL2/std.scad>
ellipse(d=[40,30], spin=30);
```
## Orientation
Another way to specify a rotation for an attachable shape, is to pass a 3D vector via the
`orient=` argument. This lets you specify what direction to tilt the top of the shape towards.
For example, you can make a cone that is tilted up and to the right like this:
```openscad-3D
include <BOSL2/std.scad>
cylinder(h=100, r1=50, r2=20, orient=UP+RIGHT);
```
More precisely, the Z direction of the shape is rotated to align with
the vector you specify. Two dimensional attachables, which have no Z vector,
do not accept the `orient=` argument.
## Mixing Anchoring, Spin, and Orientation
When giving `anchor=`, `spin=`, and `orient=`, they are applied anchoring first, spin second,
then orient last. For example, here's a cube:
```openscad-3D
include <BOSL2/std.scad>
cube([20,20,50]);
```
You can center it with an `anchor=CENTER` argument:
