Function fit_catmull_rom_indices 

pub fn fit_catmull_rom_indices(
    points: &[[f32; 3]],
    epsilon_mm: f32,
) -> Vec<usize>

Fit a Catmull-Rom curve through a sparse subset of points such that the curve stays within epsilon_mm of every input vertex. Returns the retained input indices in ascending order.

points are 3D coordinates in any consistent unit; epsilon_mm must be in the same unit. Inputs of fewer than 3 points or non-positive epsilons fall through with every index retained.

Both endpoints are always retained.