Function height_to_triangles 

pub fn height_to_triangles<F>(
    height_map: F,
    x_resolution: usize,
    z_resolution: usize,
) -> Vec<Triangle>
where
    F: Fn(usize, usize) -> f32,

Convert height map to triangles with 2x2x2 size given -1.0..=1.0 output from height_map: F