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dotSCAD/docs/lib-rotate_p.md
Justin Lin 1eb7daaf08 fixed typos
2017-03-28 20:58:57 +08:00

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# rotate_p
Rotates a point `a` degrees around an arbitrary axis. The rotation is applied in the following order: `x`, `y`, `z`.
## Parameters
- `point` : The point `[x, y, z]`.
- `a` : An array `[deg_x, deg_y, deg_z]`. The same as the `a` parameter of the built-in `rotate`.
## Examples
You can use the code below to create a line.
hull() {
sphere(1);
rotate([0, -45, 45])
translate([20, 0, 0])
sphere(1);
}
The following code has the same effect.
point = [20, 0, 0];
a = [0, -45, 45];
hull() {
sphere(1);
translate(rotate_p(point, a))
rotate(a)
sphere(1);
}
![rotate_p](images/lib-rotate_p-1.JPG)
The `rotate_p` function is useful in some situations. For examples, you probably want to get all points on the path of a spiral around a sphere.
radius = 40;
step_angle = 10;
z_circles = 20;
points_angles = [for(a = [0:step_angle:90 * z_circles])
rotate_p(
[radius, 0, 0],
[0, -90 + 2 * a / z_circles, a]
)
];
// Once you get all points on the path, you can place anything at each point.
// I just place a sphere as a simple demonstration.
for(pa = points_angles) {
translate(pa[0])
sphere(1);
}
%sphere(radius);
![rotate_p](images/lib-rotate_p-2.JPG)