File size: 2,385 Bytes
bc20498 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 |
import {cartesian, cartesianNormalizeInPlace, spherical} from "./cartesian.js";
import constant from "./constant.js";
import {acos, cos, degrees, epsilon, radians, sin, tau} from "./math.js";
import {rotateRadians} from "./rotation.js";
// Generates a circle centered at [0°, 0°], with a given radius and precision.
export function circleStream(stream, radius, delta, direction, t0, t1) {
if (!delta) return;
var cosRadius = cos(radius),
sinRadius = sin(radius),
step = direction * delta;
if (t0 == null) {
t0 = radius + direction * tau;
t1 = radius - step / 2;
} else {
t0 = circleRadius(cosRadius, t0);
t1 = circleRadius(cosRadius, t1);
if (direction > 0 ? t0 < t1 : t0 > t1) t0 += direction * tau;
}
for (var point, t = t0; direction > 0 ? t > t1 : t < t1; t -= step) {
point = spherical([cosRadius, -sinRadius * cos(t), -sinRadius * sin(t)]);
stream.point(point[0], point[1]);
}
}
// Returns the signed angle of a cartesian point relative to [cosRadius, 0, 0].
function circleRadius(cosRadius, point) {
point = cartesian(point), point[0] -= cosRadius;
cartesianNormalizeInPlace(point);
var radius = acos(-point[1]);
return ((-point[2] < 0 ? -radius : radius) + tau - epsilon) % tau;
}
export default function() {
var center = constant([0, 0]),
radius = constant(90),
precision = constant(2),
ring,
rotate,
stream = {point: point};
function point(x, y) {
ring.push(x = rotate(x, y));
x[0] *= degrees, x[1] *= degrees;
}
function circle() {
var c = center.apply(this, arguments),
r = radius.apply(this, arguments) * radians,
p = precision.apply(this, arguments) * radians;
ring = [];
rotate = rotateRadians(-c[0] * radians, -c[1] * radians, 0).invert;
circleStream(stream, r, p, 1);
c = {type: "Polygon", coordinates: [ring]};
ring = rotate = null;
return c;
}
circle.center = function(_) {
return arguments.length ? (center = typeof _ === "function" ? _ : constant([+_[0], +_[1]]), circle) : center;
};
circle.radius = function(_) {
return arguments.length ? (radius = typeof _ === "function" ? _ : constant(+_), circle) : radius;
};
circle.precision = function(_) {
return arguments.length ? (precision = typeof _ === "function" ? _ : constant(+_), circle) : precision;
};
return circle;
}
|