Function sample_catmull_rom_into 

pub fn sample_catmull_rom_into(
    cps: &[[f32; 3]],
    samples_per_segment: usize,
    out: &mut Vec<[f32; 3]>,
)

Sample a Catmull-Rom curve into a caller-provided buffer. The buffer is cleared first; capacity is reused. Useful in tight loops to avoid per-call allocations.