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Tweaks to Attachments tutorial.

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Garth Minette 2021-10-06 21:40:47 -07:00
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tutorials/Attachments.md
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@ -5,8 +5,8 @@
## 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.
`cube()`, `cylinder()`, `sphere()`, `square()`, and `circle()`. BOSL2 overrides the built-in
definitions for these shapes, and makes them attachable.
## Anchoring
@ -44,6 +44,10 @@ Constant | Direction | Value
`TOP`/`UP` | Z+ | `[ 0, 0, 1]` (3D only.)
`CENTER`/`CTR` | Centered | `[ 0, 0, 0]`
If you want a vector pointing towards the bottom-left edge, just add the `BOTTOM` and `LEFT` vector
constants together like `BOTTOM + LEFT`. Ths will result in a vector of `[-1,0,-1]`. You can pass
that to the `anchor=` argument for a clearly understandable anchoring:
```openscad-3D
cube([40,30,50], anchor=BACK+TOP);
```
@ -54,9 +58,11 @@ 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:
For cylindrical type attachables, the Z component of the vector will be -1, 0, or 1, referring
to the bottom rim, the middle side, or the top rim of the cylindrical or conical shape.
The X and Y components can be any value, pointing towards the circular perimeter of the cone.
These combined let you point at any place on the bottom or top rims, or at an arbitrary
side wall:
```openscad-3D
cylinder(r1=25, r2=15, h=60, anchor=TOP+LEFT);
@ -72,8 +78,8 @@ 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:
For Spherical type attachables, you can pass a vector that points at any arbitrary place on
the surface of the sphere:
```openscad-3D
sphere(r=50, anchor=TOP);
@ -90,7 +96,8 @@ 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:
will be given as strings and will be specific to that type of attachable. For example, the
`teardrop()` attachable has a named anchor called "cap":
```openscad-3D
teardrop(d=100, l=20, anchor="cap");
@ -101,7 +108,15 @@ 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.
cylinder, to make them behave just like the builtin versions:
```openscad-3D
cube([50,40,30],center=true);
```
```openscad-3D
cube([50,40,30],center=false);
```
---
@ -127,15 +142,18 @@ oval(d=[50,30], anchor=FRONT);
## 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:
Attachable shapes also can be spun in place as you create them. You can do this by passing the
spin angle (in degrees) into the `spin=` argument. 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
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]:
You can even spin around each of the three axes in one pass, by giving 3 angles (in degrees) to
`spin=` as a vector, like [Xang,Yang,Zang]. Similarly to `rotate()`, the axes will be spun in
the order given, X-axis spin, then Y-axis, then Z-axis:
```openscad-3D
cube([20,20,40], center=true, spin=[10,20,30]);