Function forsyth::order_vertices

pub fn order_vertices<Index, Vertex>(
    vertices: &[Vertex], 
    indices: &[Index]
) -> Result<(Vec<Vertex>, Vec<Index>), String> where
    Index: Copy + Eq + TryInto<usize> + TryFrom<usize> + Hash,
    Vertex: Copy, 

Orders a vertex buffer to maximize data locality.

The returned vertex buffer contains the referenced vertices from vertices and is ordered to maximize data locality when being read sequentially. The accompanying index buffer contains the mapped indices to match the new vertex ordering.

This function can also be used to consolidate sparse index and vertex data as unreferenced vertices are not copied.

use forsyth::order_vertices;

assert_eq!(
    order_vertices(&['d', 'c', 'b', 'a'], &[3, 2, 0, 2, 1, 0]),
    Ok((vec!['a', 'b', 'd', 'c'], vec![0, 1, 2, 1, 3, 2]))
);

// Vertices not referenced by any index are removed
assert_eq!(
    order_vertices(&['x', 'x', 'a', 'b', 'y', 'c'], &[2, 3, 5]),
    Ok((vec!['a', 'b', 'c'], vec![0, 1, 2]))
);

// Indices must be in valid range
assert_eq!(
    order_vertices(&['a', 'b', 'c'], &[0_i8, 1, 99]),
    Err("index does not point into vertex array (out-of-bounds)".to_string())
);
assert_eq!(
    order_vertices(&['a', 'b', 'c'], &[0_i8, -1, 2]),
    Err("failed to convert Index to usize".to_string())
);