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use core::ops::{Mul, Sub}; use cast_trait::Cast; use num_traits::{FromPrimitive, One, Zero}; use vec2; #[inline] pub fn cubic<'out, T, F>( out: &'out mut [T; 2], p0: &[T; 2], p1: &[T; 2], p2: &[T; 2], t: &F, ) -> &'out mut [T; 2] where T: Clone + Cast<F>, F: Clone + One + Zero + FromPrimitive + PartialOrd + Cast<T>, for<'a, 'b> &'a F: Sub<&'b F, Output = F> + Mul<&'b F, Output = F>, { if t <= &F::zero() { *out = p0.clone(); out } else if t >= &F::one() { *out = p2.clone(); out } else { let two = F::from_usize(2).unwrap(); let one_min_t = &F::one() - t; let one_min_t_sq = &one_min_t * &one_min_t; let t_sq = t * t; let p0x = p0[0].clone().cast(); let p0y = p0[1].clone().cast(); let p1x = p1[0].clone().cast(); let p1y = p1[1].clone().cast(); let p2x = p2[0].clone().cast(); let p2y = p2[1].clone().cast(); vec2::set( out, (one_min_t_sq.clone() * p0x + two.clone() * one_min_t.clone() * t.clone() * p1x + t_sq.clone() * p2x) .cast(), (one_min_t_sq * p0y + two * one_min_t * t.clone() * p1y + t_sq * p2y).cast(), ) } } #[test] fn test_cubic() { assert_eq!( cubic(&mut [0, 0], &[0, 0], &[100, 200], &[200, 0], &0.25), &[50, 75] ); assert_eq!( cubic(&mut [0, 0], &[0, 0], &[100, 200], &[200, 0], &0.5), &[100, 100] ); assert_eq!( cubic(&mut [0, 0], &[0, 0], &[100, 200], &[200, 0], &0.75), &[150, 75] ); }