BOSL2/tutorials/Attachments.md

Attachments Tutorial

Attachables

BOSL2 introduces the concept of attachables. Attachables are shapes that can be anchored, spun, oriented, and attached to other attachables. The most basic attachable shapes are the cube(), cylinder(), and sphere(). BOSL2 overrides the built-in definitions for these shapes, and makes them attachables.

Anchoring

Anchoring allows you to align a side, edge, or corner of an object with the origin as it is created. This is done by passing a vector into the anchor= argument. For roughly cubical or prismoidal shapes, that vector points in the general direction of the side, edge, or corner that will be aligned to. Each vector component should be -1, 0, or 1:

cube([40,30,50], anchor=[-1,-1,1]);

cube([40,30,50], anchor=[1,0,1]);

cube([40,30,50], anchor=[0,0,-1]);

Since manually written vectors are not very intuitive, BOSL2 defines some standard directional vector constants that can be added together:

Constant	Direction	Value
LEFT	X-	[-1, 0, 0]
RIGHT	X+	[ 1, 0, 0]
FRONT/FORWARD/FWD	Y-	[ 0,-1, 0]
BACK	Y+	[ 0, 1, 0]
BOTTOM/BOT/BTM/DOWN	Z-	[ 0, 0,-1] (3D only.)
TOP/UP	Z+	[ 0, 0, 1] (3D only.)
CENTER/CTR	Centered	[ 0, 0, 0]

cube([40,30,50], anchor=BACK+TOP);

cube([40,30,50], anchor=FRONT);

Cylindrical attachables can be anchored similarly, except that only the Z vector component is required to be -1, 0, or 1. This allows anchoring to arbitrary edges around the cylinder or cone:

cylinder(r1=25, r2=15, h=60, anchor=TOP+LEFT);

cylinder(r1=25, r2=15, h=60, anchor=BOTTOM+FRONT);

cylinder(r1=25, r2=15, h=60, anchor=UP+spherical_to_xyz(1,30,90));

Spherical shapes can use fully proportional anchoring vectors, letting you anchor to any point on the surface of the sphere, just by pointing a vector at it:

sphere(r=50, anchor=TOP);

sphere(r=50, anchor=TOP+FRONT);

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:

teardrop(d=100, l=20, anchor="cap");

Some shapes, for backwards compatability 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 can mean anchor=[-1,-1,-1] for a cube, or anchor=BOTTOM for a cylinder.

Spin

Attachable shapes also can be spun in place as you create them. You can do this by passing in the angle to spin by into the spin= argument:

cube([20,20,40], center=true, spin=45);

You can even spin around each of the three axes in one pass, by giving 3 angles to spin= as a vector, like [Xang,Yang,Zang]:

cube([20,20,40], center=true, spin=[10,20,30]);

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:

cylinder(h=100, r1=50, r2=20, orient=UP+RIGHT);

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:

cube([20,20,50]);

You can center it with an anchor=CENTER argument:

cube([20,20,50], anchor=CENTER);

Add a 45 degree spin:

cube([20,20,50], anchor=CENTER, spin=45);

Now tilt the top up and forward:

cube([20,20,50], anchor=CENTER, spin=45, orient=UP+FWD);

Something that may confuse new users is that adding spin to a cylinder may seem nonsensical. However, since spin is applied after anchoring, it can actually have a significant effect:

cylinder(d=50, l=40, anchor=FWD, spin=-30);

Attaching Children

The reason attachables are called that, is because they can be attached to each other. You can do that by making one attachable shape be a child of another attachable shape. By default, the child of an attachable is attached to the center of the parent shape.

cube(50,center=true)
    cylinder(d1=50,d2=20,l=50);

To attach to a different place on the parent, you can use the attach() module. By default, this will attach the bottom of the child to the given position on the parent. The orientation of the child will be overridden to point outwards from the center of the parent, more or less:

cube(50,center=true)
    attach(TOP) cylinder(d1=50,d2=20,l=20);

If you give attach() a second anchor argument, it attaches that anchor on the child to the first anchor on the parent:

cube(50,center=true)
    attach(TOP,TOP) cylinder(d1=50,d2=20,l=20);

By default, attach() causes the child to overlap the parent by 0.01, to let CGAL correctly join the parts. If you need the child to have no overlap, or a different overlap, you can use the overlap= argument:

cube(50,center=true)
    attach(TOP,TOP,overlap=0) cylinder(d1=50,d2=20,l=20);

If you want to position the child at the parent's anchorpoint, without re-orienting, you can use the position() module:

cube(50,center=true)
    position(RIGHT) cylinder(d1=50,d2=20,l=20);

You can attach or position more than one child at a time by enclosing them all in braces:

cube(50, center=true) {
    attach(TOP) cylinder(d1=50,d2=20,l=20);
    position(RIGHT) cylinder(d1=50,d2=20,l=20);
}

Or, if you want to attach the same shape to multiple places on the parent, you can pass the anchors as a list to the attach() or position() modules:

cube(50, center=true)
    attach([RIGHT,FRONT],TOP) cylinder(d1=50,d2=20,l=20);

cube(50, center=true)
    position([TOP,RIGHT,FRONT]) cylinder(d1=50,d2=20,l=20);

Boolean Operations

Masking Children

edge_mask() corner_mask()

face_profile() edge_profile() corner_profile()

Coloring Attachables

Making Attachables

Making Named Anchors