# bspline_curve

B-spline interpolation using de Boor's algorithm. This function returns points of the B-spline path. Combined with the `polyline`, `polyline3d` or `hull_polyline3d` module, you can create a B-spline curve.

Since: 2.1

## Parameters

• `t_step` : The increment amount along the curve in the [0, 1] range.
• `degree` : The degree of B-spline. Must be less than or equal to `len(points) - 1`.
• `points` : A list of `[x, y]` or `[x, y, z]` control points.
• `knots` : The knot vector. It's a non-decreasing sequence with length `len(points) + degree + 1`. If not provided, a uniform knot vector is generated automatically.
• `weights` : The weights of control points. If not provided, the weight of each point is 1.

## Examples

``````use <bspline_curve.scad>;

points = [
[-10, 0],
[-5,  5],
[ 5, -5],
[ 10, 0]
];

color("red") for(p = points) {
translate(p)
sphere(0.5);
}

// knots: [0, 1, 2, 3, 4, 5, 6]
// weights: [1, 1, 1, 1]
for(p = bspline_curve(0.01, 2, points)) {
translate(p)
sphere(0.1);
}
`````` ``````use <bspline_curve.scad>;

points = [
[-10, 0],
[-5,  5],
[ 5, -5],
[ 10, 0]
];

// a non-uniform B-spline curve
knots = [0, 1/8, 1/4, 1/2, 3/4, 4/5, 1];

color("red") for(p = points) {
translate(p)
sphere(0.5);
}

for(p = bspline_curve(0.01, 2, points, knots)) {
translate(p)
sphere(0.1);
}
`````` ``````use <bspline_curve.scad>;

points = [
[-10, 0],
[-5,  5],
[ 5, -5],
[ 10, 0]
];

// For a clamped B-spline curve, the first `degree + 1` and the last `degree + 1` knots must be identical.
knots = [0, 0, 0, 1, 2, 2, 2];

color("red") for(p = points) {
translate(p)
sphere(0.5);
}

for(p = bspline_curve(0.01, 2, points, knots)) {
translate(p)
sphere(0.1);
}
`````` 