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Implement functions to create a Bezier that goes through 3 specified points (#687)

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* Implement quadratic and cubic from points

* Catch edge cases and integrate `t` slider

* Add 2 sliders for cubic

* Create utils file for bezier-rs and address other PR comments

* Rename variable and remove unnecessary ids

* Update rustdoc comments and rename variables

* Remove unnecessary file and refactor options for drawing beziers

* Address PR comments

* Update quadratic_through_points description

* Add wasm-pack to dependencies and change from spaces to tabs for indents

* Change strut to midpoint_separation, adjust sliders and section name

* Minor refactor
This commit is contained in:
Hannah Li
2022-06-29 20:52:09 -04:00
committed by Keavon Chambers
parent 4eaffd0e5a
commit 2e3e079982
13 changed files with 19471 additions and 19055 deletions
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bezier-rs/lib/src/utils.rs
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use glam::DVec2;
/// Helper to perform the computation of a and c, where b is the provided point on the curve.
/// Given the correct power of `t` and `(1-t)`, the computation is the same for quadratic and cubic cases.
/// Relevant derivation and the definitions of a, b, and c can be found in [the projection identity section](https://pomax.github.io/bezierinfo/#abc) of Pomax's bezier curve primer.
fn compute_abc_through_points(start_point: DVec2, point_on_curve: DVec2, end_point: DVec2, t_to_nth_power: f64, nth_power_of_one_minus_t: f64) -> [DVec2; 3] {
let point_c_ratio = nth_power_of_one_minus_t / (t_to_nth_power + nth_power_of_one_minus_t);
let c = point_c_ratio * start_point + (1. - point_c_ratio) * end_point;
let ab_bc_ratio = (t_to_nth_power + nth_power_of_one_minus_t - 1.).abs() / (t_to_nth_power + nth_power_of_one_minus_t);
let a = point_on_curve + (point_on_curve - c) / ab_bc_ratio;
[a, point_on_curve, c]
}
/// Compute a, b, and c for a quadratic curve that fits the start, end and point on curve at `t`.
/// The definition for the a, b, c points are defined in [the projection identity section](https://pomax.github.io/bezierinfo/#abc) of Pomax's bezier curve primer.
pub fn compute_abc_for_quadratic_through_points(start_point: DVec2, point_on_curve: DVec2, end_point: DVec2, t: f64) -> [DVec2; 3] {
let t_squared = t * t;
let one_minus_t = 1. - t;
let squared_one_minus_t = one_minus_t * one_minus_t;
compute_abc_through_points(start_point, point_on_curve, end_point, t_squared, squared_one_minus_t)
}
/// Compute a, b, and c for a cubic curve that fits the start, end and point on curve at `t`.
/// The definition for the a, b, c points are defined in [the projection identity section](https://pomax.github.io/bezierinfo/#abc) of Pomax's bezier curve primer.
pub fn compute_abc_for_cubic_through_points(start_point: DVec2, point_on_curve: DVec2, end_point: DVec2, t: f64) -> [DVec2; 3] {
let t_cubed = t * t * t;
let one_minus_t = 1. - t;
let cubed_one_minus_t = one_minus_t * one_minus_t * one_minus_t;
compute_abc_through_points(start_point, point_on_curve, end_point, t_cubed, cubed_one_minus_t)
}