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#[derive(Debug, Clone, Copy)]
pub struct RubberBand {
pub stiffness: f64,
pub limit: f64,
}
impl RubberBand {
pub fn band(&self, x: f64) -> f64 {
let c = self.stiffness;
let d = self.limit;
(1. - (1. / (x * c / d + 1.))) * d
}
pub fn derivative(&self, x: f64) -> f64 {
let c = self.stiffness;
let d = self.limit;
c * d * d / (c * x + d).powi(2)
}
pub fn clamp(&self, min: f64, max: f64, x: f64) -> f64 {
let clamped = x.clamp(min, max);
let sign = if x < clamped { -1. } else { 1. };
let diff = (x - clamped).abs();
clamped + sign * self.band(diff)
}
pub fn clamp_derivative(&self, min: f64, max: f64, x: f64) -> f64 {
if min <= x && x <= max {
return 1.;
}
let clamped = x.clamp(min, max);
let diff = (x - clamped).abs();
self.derivative(diff)
}
}
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