del_msh_cpu/

io_wavefront_obj.rs

//! methods for Wavefront Obj files

use anyhow::Context;
use num_traits::AsPrimitive;
use std::fs::File;
use std::io::{BufRead, BufReader, Write};
use std::ops::AddAssign;

pub struct WavefrontObj<Index, Real> {
    pub vtx2xyz: Vec<Real>,
    pub vtx2uv: Vec<Real>,
    pub vtx2nrm: Vec<Real>,
    pub elem2idx: Vec<Index>,
    pub idx2vtx_xyz: Vec<Index>,
    pub idx2vtx_uv: Vec<Index>,
    pub idx2vtx_nrm: Vec<Index>,
    pub elem2group: Vec<Index>,
    pub group2name: Vec<String>,
    pub elem2mtl: Vec<Index>,
    pub mtl_file_name: String,
    pub mtl2name: Vec<String>,
}

impl<Index, Real> WavefrontObj<Index, Real>
where
    Real: std::str::FromStr + std::fmt::Display + Copy + num_traits::Zero,
    Index: num_traits::PrimInt + 'static + AddAssign + AsPrimitive<usize> + Copy,
    usize: AsPrimitive<Index>,
    i32: AsPrimitive<Index>,
{
    pub fn new() -> Self {
        WavefrontObj::<Index, Real> {
            vtx2xyz: Vec::new(),
            vtx2uv: Vec::new(),
            vtx2nrm: Vec::new(),
            elem2idx: Vec::new(),
            idx2vtx_uv: Vec::new(),
            idx2vtx_nrm: Vec::new(),
            idx2vtx_xyz: Vec::new(),
            elem2group: Vec::new(),
            group2name: Vec::new(),
            mtl_file_name: "".to_string(),
            elem2mtl: Vec::new(),
            mtl2name: Vec::new(),
        }
    }

    /// load wavefront obj file into the class
    pub fn load<P: AsRef<std::path::Path>>(&mut self, filename: P) -> anyhow::Result<()> {
        let mut elem2vtx_xyz0: Vec<i32> = vec![];
        let mut elem2vtx_uv0: Vec<i32> = vec![];
        let mut elem2vtx_nrm0: Vec<i32> = vec![];
        self.elem2group.clear();
        self.elem2mtl.clear();
        self.elem2idx = vec![Index::zero()];
        let mut name2group = std::collections::BTreeMap::<String, usize>::new();
        let mut name2mtl = std::collections::BTreeMap::<String, usize>::new();
        name2group.insert("_default".to_string(), 0);
        name2mtl.insert("_default".to_string(), 0);
        let mut i_group = 0_usize;
        let mut i_mtl = 0_usize;
        let f = File::open(filename).context("file not found")?;
        let reader = BufReader::new(f);
        for line in reader.lines() {
            let line = line.unwrap();
            if line.is_empty() {
                continue;
            }
            let char0 = line.chars().next();
            if char0.is_none() {
                continue;
            }
            let char0 = char0.unwrap();
            let char1 = line.chars().nth(1);
            if char1.is_none() {
                continue;
            }
            let char1 = char1.unwrap();
            if char0 == '#' {
                continue;
            }
            if char0 == 'v' && char1 == ' ' {
                let v: Vec<&str> = line.split_whitespace().collect();
                let x = v[1].parse::<Real>().ok().unwrap();
                let y = v[2].parse::<Real>().ok().unwrap();
                let z = v[3].parse::<Real>().ok().unwrap();
                self.vtx2xyz.push(x);
                self.vtx2xyz.push(y);
                self.vtx2xyz.push(z);
            }
            if char0 == 'g' && char1 == ' ' {
                let v: Vec<&str> = line.split_whitespace().collect();
                let name = v[1].to_string();
                match name2group.get(&name) {
                    None => {
                        i_group = name2group.len();
                        name2group.insert(name, i_group);
                    }
                    Some(&v) => {
                        i_group = v;
                    }
                };
            }
            if char0 == 'm' && char1 == 't' {
                let v: Vec<&str> = line.split_whitespace().collect();
                self.mtl_file_name = v[1].to_string();
            }
            if char0 == 'u' && char1 == 's' {
                let v: Vec<&str> = line.split_whitespace().collect();
                let name = v[1].to_string();
                match name2mtl.get(&name) {
                    None => {
                        i_mtl = name2mtl.len();
                        name2mtl.insert(name, i_mtl);
                    }
                    Some(&v) => {
                        i_mtl = v;
                    }
                };
            }
            if char0 == 'v' && char1 == 'n' {
                let v: Vec<&str> = line.split_whitespace().collect();
                let x = v[1].parse::<Real>().ok().unwrap();
                let y = v[2].parse::<Real>().ok().unwrap();
                let z = v[3].parse::<Real>().ok().unwrap();
                self.vtx2nrm.push(x);
                self.vtx2nrm.push(y);
                self.vtx2nrm.push(z);
            }
            if char0 == 'v' && char1 == 't' {
                let v: Vec<&str> = line.split_whitespace().collect();
                let u = v[1].parse::<Real>().ok().unwrap();
                let v = v[2].parse::<Real>().ok().unwrap();
                self.vtx2uv.push(u);
                self.vtx2uv.push(v);
            }
            if char0 == 'f' && char1 == ' ' {
                let v: Vec<&str> = line.split_whitespace().collect();
                for v_ in v.iter().skip(1) {
                    // skip first 'f'
                    let (ipnt, itex, inrm) = parse_vertex(v_);
                    elem2vtx_xyz0.push(ipnt);
                    elem2vtx_uv0.push(itex);
                    elem2vtx_nrm0.push(inrm);
                }
                self.elem2idx.push(elem2vtx_xyz0.len().as_());
                self.elem2group.push(i_group.as_());
                self.elem2mtl.push(i_mtl.as_());
            }
        } // end loop over text
        self.group2name = vec!["".to_string(); name2group.len()];
        for (name, &i_group) in name2group.iter() {
            self.group2name[i_group].clone_from(name);
        }
        self.mtl2name = vec!["".to_string(); name2mtl.len()];
        for (name, &i_mtl) in name2mtl.iter() {
            self.mtl2name[i_mtl].clone_from(name);
        }
        {
            // fix veretx_xyz index
            let nvtx_xyz = self.vtx2xyz.len() / 3;
            self.idx2vtx_xyz = elem2vtx_xyz0
                .iter()
                .map(|i| {
                    if *i >= 0 {
                        (*i).as_()
                    } else {
                        (nvtx_xyz as i32 + *i).as_()
                    }
                })
                .collect();
        }
        {
            // fix veretx_uv index
            let nvtx_uv = self.vtx2uv.len() / 3;
            self.idx2vtx_uv = elem2vtx_uv0
                .iter()
                .map(|i| {
                    if *i >= 0 {
                        (*i).as_()
                    } else {
                        (nvtx_uv as i32 + *i).as_()
                    }
                })
                .collect();
        }
        {
            // fix veretx_nrm index
            let nvtx_nrm = self.vtx2nrm.len() / 3;
            self.idx2vtx_nrm = elem2vtx_nrm0
                .iter()
                .map(|i| {
                    if *i >= 0 {
                        (*i).as_()
                    } else {
                        (nvtx_nrm as i32 + *i).as_()
                    }
                })
                .collect();
        }
        Ok(())
    }

    pub fn unified_xyz_uv_as_trimesh(&self) -> (Vec<Index>, Vec<Real>, Vec<Real>) {
        let (tri2uni, uni2vtx_xyz, uni2vtx_uv) =
            crate::unify_index::unify_two_indices_of_triangle_mesh(
                &self.idx2vtx_xyz,
                &self.idx2vtx_uv,
            );
        assert_eq!(uni2vtx_xyz.len(), uni2vtx_uv.len());
        let uni2xyz = crate::map_idx::map_vertex_attibute_from(&self.vtx2xyz, 3, &uni2vtx_xyz);
        let uni2uv = crate::map_idx::map_vertex_attibute_from(&self.vtx2uv, 2, &uni2vtx_uv);
        (tri2uni, uni2xyz, uni2uv)
    }
}

impl<Index, Real> Default for WavefrontObj<Index, Real>
where
    Real: std::str::FromStr + std::fmt::Display + Copy + num_traits::Zero,
    Index: num_traits::PrimInt + 'static + AddAssign + AsPrimitive<usize> + Copy,
    usize: AsPrimitive<Index>,
    i32: AsPrimitive<Index>,
{
    fn default() -> Self {
        Self::new()
    }
}

pub fn load_tri_mesh<P: AsRef<std::path::Path>, Index, Real>(
    filepath: P,
    scale: Option<Real>,
) -> anyhow::Result<(Vec<Index>, Vec<Real>)>
where
    Real: std::str::FromStr + std::fmt::Display + num_traits::Float,
    Index: num_traits::PrimInt + 'static + AddAssign + AsPrimitive<usize> + Copy,
    usize: AsPrimitive<Index>,
    i32: AsPrimitive<Index>,
{
    let mut obj = WavefrontObj::<Index, Real>::new();
    obj.load(&filepath)?;
    let tri2vtx = obj.idx2vtx_xyz;
    let mut vtx2xyz = obj.vtx2xyz;
    if let Some(scale_) = scale {
        // scale the vertex positions if scale is provided
        crate::vtx2xyz::normalize_in_place(&mut vtx2xyz, scale_);
    }
    Ok((tri2vtx, vtx2xyz))
}

pub fn save_tri_mesh_texture(
    filepath: &str,
    tri2vtx_xyz: &[usize],
    vtx2xyz: &[f32],
    tri2vtx_uv: &[usize],
    vtx2uv: &[f32],
) -> anyhow::Result<()> {
    assert_eq!(tri2vtx_xyz.len(), tri2vtx_uv.len());
    let mut file = File::create(filepath).context("file not found.")?;
    for i_vtx in 0..vtx2xyz.len() / 3 {
        writeln!(
            file,
            "v {} {} {}",
            vtx2xyz[i_vtx * 3],
            vtx2xyz[i_vtx * 3 + 1],
            vtx2xyz[i_vtx * 3 + 2]
        )?;
    }
    for i_vtx in 0..vtx2uv.len() / 2 {
        writeln!(file, "vt {} {}", vtx2uv[i_vtx * 2], vtx2uv[i_vtx * 2 + 1])?;
    }
    for i_tri in 0..tri2vtx_xyz.len() / 3 {
        writeln!(
            file,
            "f {}/{} {}/{} {}/{}",
            tri2vtx_xyz[i_tri * 3] + 1,
            tri2vtx_uv[i_tri * 3] + 1,
            tri2vtx_xyz[i_tri * 3 + 1] + 1,
            tri2vtx_uv[i_tri * 3 + 1] + 1,
            tri2vtx_xyz[i_tri * 3 + 2] + 1,
            tri2vtx_uv[i_tri * 3 + 2] + 1
        )?;
    }
    Ok(())
}

fn write_vtx2xyz<Real>(
    file: &mut std::io::BufWriter<File>,
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Real: std::fmt::Display,
{
    match num_dim {
        3_usize => {
            for i_vtx in 0..vtx2xyz.len() / 3 {
                writeln!(
                    file,
                    "v {} {} {}",
                    vtx2xyz[i_vtx * 3],
                    vtx2xyz[i_vtx * 3 + 1],
                    vtx2xyz[i_vtx * 3 + 2]
                )?;
            }
        }
        2_usize => {
            for i_vtx in 0..vtx2xyz.len() / 2 {
                writeln!(
                    file,
                    "v {} {} {}",
                    vtx2xyz[i_vtx * 2],
                    vtx2xyz[i_vtx * 2 + 1],
                    0.
                )?;
            }
        }
        _ => {
            panic!("dimension should be either 2 or 3");
        }
    }
    Ok(())
}

fn write_vtx2nrm<Real>(file: &mut std::io::BufWriter<File>, vtx2nrm: &[Real]) -> anyhow::Result<()>
where
    Real: std::fmt::Display,
{
    for i_vtx in 0..vtx2nrm.len() / 3 {
        writeln!(
            file,
            "vn {} {} {}",
            vtx2nrm[i_vtx * 3],
            vtx2nrm[i_vtx * 3 + 1],
            vtx2nrm[i_vtx * 3 + 2]
        )?;
    }
    Ok(())
}

fn write_vtx2xyz_vtx2rgb<Real>(
    file: &mut std::io::BufWriter<File>,
    vtx2xyz: &[Real],
    vtx2rgb: &[f32],
) -> anyhow::Result<()>
where
    Real: std::fmt::Display,
{
    for i_vtx in 0..vtx2xyz.len() / 3 {
        writeln!(
            file,
            "v {} {} {} {} {} {}",
            vtx2xyz[i_vtx * 3],
            vtx2xyz[i_vtx * 3 + 1],
            vtx2xyz[i_vtx * 3 + 2],
            vtx2rgb[i_vtx * 3],
            vtx2rgb[i_vtx * 3 + 1],
            vtx2rgb[i_vtx * 3 + 2]
        )?;
    }
    Ok(())
}

fn write_vtx2vecn<Real, const N: usize>(
    file: &mut std::io::BufWriter<File>,
    vtx2vecn: &[[Real; N]],
) -> anyhow::Result<()>
where
    Real: num_traits::Float + std::fmt::Display,
{
    match N {
        3_usize => {
            for vtx in vtx2vecn {
                writeln!(file, "v {} {} {}", vtx[0], vtx[1], vtx[2])?;
            }
        }
        2_usize => {
            for vtx in vtx2vecn {
                writeln!(file, "v {} {} {}", vtx[0], vtx[1], 0.)?;
            }
        }
        _ => {
            panic!();
        }
    }
    Ok(())
}

pub fn save_tri2vtx_vtx2xyz<Path, Index, Real>(
    filepath: Path,
    tri2vtx: &[Index],
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
    Index: num_traits::PrimInt + std::fmt::Display,
{
    let file = File::create(&filepath)
        .context(format!("file not found. {}", filepath.as_ref().display()))?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    for i_tri in 0..tri2vtx.len() / 3 {
        writeln!(
            file,
            "f {} {} {}",
            tri2vtx[i_tri * 3] + Index::one(),
            tri2vtx[i_tri * 3 + 1] + Index::one(),
            tri2vtx[i_tri * 3 + 2] + Index::one()
        )?;
    }
    Ok(())
}

pub fn save_tri2vtx_vtx2xyz_vtx2rgb<Path, Index, Real>(
    filepath: Path,
    tri2vtx: &[Index],
    vtx2xyz: &[Real],
    vtx2rgb: &[f32],
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
    Index: num_traits::PrimInt + std::fmt::Display,
{
    let file = File::create(filepath).context("file not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz_vtx2rgb(&mut file, vtx2xyz, vtx2rgb)?;
    for i_tri in 0..tri2vtx.len() / 3 {
        writeln!(
            file,
            "f {} {} {}",
            tri2vtx[i_tri * 3] + Index::one(),
            tri2vtx[i_tri * 3 + 1] + Index::one(),
            tri2vtx[i_tri * 3 + 2] + Index::one()
        )?;
    }
    Ok(())
}

pub fn save_tri2vtx_vtx2xyz_vtx2nrm<Path, Index, Real>(
    filepath: Path,
    tri2vtx: &[Index],
    vtx2xyz: &[Real],
    vtx2nrm: &[Real],
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
    Index: num_traits::PrimInt + std::fmt::Display,
{
    let file = File::create(filepath).context("file not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, 3)?;
    write_vtx2nrm(&mut file, vtx2nrm)?;
    for i_tri in 0..tri2vtx.len() / 3 {
        let i0 = tri2vtx[i_tri * 3] + Index::one();
        let i1 = tri2vtx[i_tri * 3 + 1] + Index::one();
        let i2 = tri2vtx[i_tri * 3 + 2] + Index::one();
        writeln!(file, "f {i0}//{i0} {i1}//{i1} {i2}//{i2}")?;
    }
    Ok(())
}

pub fn save_tri2vtx_vtx2vecn<Path, Real, const N: usize>(
    filepath: Path,
    tri2vtx: &[usize],
    vtx2vecn: &[[Real; N]],
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2vecn(&mut file, vtx2vecn)?;
    for tri in tri2vtx.chunks(3) {
        writeln!(file, "f {} {} {}", tri[0] + 1, tri[1] + 1, tri[2] + 1)?;
    }
    Ok(())
}

pub fn save_vtx2xyz_as_polyloop<Path, Real>(
    filepath: Path,
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    let num_vtx = vtx2xyz.len() / num_dim;
    for i_vtx in 0..num_vtx {
        let i0 = i_vtx;
        let i1 = (i_vtx + 1) % num_vtx;
        writeln!(file, "l {} {}", i0 + 1, i1 + 1)?;
    }
    Ok(())
}

pub fn save_vtx2vecn_as_polyloop<Path, Real, const N: usize>(
    filepath: Path,
    vtx2vecn: &[[Real; N]],
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2vecn(&mut file, vtx2vecn)?;
    let num_vtx = vtx2vecn.len();
    for i_vtx in 0..num_vtx {
        let i0 = i_vtx;
        let i1 = (i_vtx + 1) % num_vtx;
        writeln!(file, "l {} {}", i0 + 1, i1 + 1)?;
    }
    Ok(())
}

// ------------------------

pub fn save_vtx2xyz_as_polyline<Path, Real>(
    filepath: Path,
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    let num_vtx = vtx2xyz.len() / num_dim;
    for i_vtx in 0..num_vtx - 1 {
        let i0 = i_vtx;
        let i1 = i_vtx + 1;
        writeln!(file, "l {} {}", i0 + 1, i1 + 1)?;
    }
    Ok(())
}

// ------------------------

pub fn save_edge2vtx_vtx2xyz<Path, Real>(
    filepath: Path,
    edge2vtx: &[usize],
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file  not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    // let num_vtx = vtx2xyz.len() / num_dim;
    for node2vtx in edge2vtx.chunks(2) {
        let (i0, i1) = (node2vtx[0], node2vtx[1]);
        writeln!(file, "l {} {}", i0 + 1, i1 + 1)?;
    }
    Ok(())
}

pub fn save_polyline2vtx_vtx2xyz<Path, Real>(
    filepath: Path,
    polyline2vtx: &[usize],
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file  not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    // let num_vtx = vtx2xyz.len() / num_dim;
    for i_poly in 0..polyline2vtx.len() - 1 {
        let num_vtx_in_polyline = polyline2vtx[i_poly + 1] - polyline2vtx[i_poly];
        for i_vtx in 0..num_vtx_in_polyline - 1 {
            let i0 = polyline2vtx[i_poly] + i_vtx;
            let i1 = polyline2vtx[i_poly] + i_vtx + 1;
            writeln!(file, "l {} {}", i0 + 1, i1 + 1)?;
        }
    }
    Ok(())
}

pub fn save_quad2vtx_vtx2xyz<Path, Real>(
    filepath: Path,
    quad2vtx: &[usize],
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file  not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    // let num_vtx = vtx2xyz.len() / num_dim;
    for node2vtx in quad2vtx.chunks(4) {
        let i0 = node2vtx[0];
        let i1 = node2vtx[1];
        let i2 = node2vtx[2];
        let i3 = node2vtx[3];
        writeln!(file, "f {} {} {} {}", i0 + 1, i1 + 1, i2 + 1, i3 + 1)?;
    }
    Ok(())
}

pub fn save_elem2idx_idx2vtx_vtx2xyz<Path, Real>(
    filepath: Path,
    elem2idx: &[usize],
    idx2vtx: &[usize],
    vtx2xyz: &[Real],
    num_dim: usize,
) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file  not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, vtx2xyz, num_dim)?;
    // let num_vtx = vtx2xyz.len() / num_dim;
    for i_elem in 0..elem2idx.len() - 1 {
        let noel = &idx2vtx[elem2idx[i_elem]..elem2idx[i_elem + 1]];
        match noel.len() {
            3 => writeln!(file, "f {} {} {}", noel[0] + 1, noel[1] + 1, noel[2] + 1)?,
            4 => writeln!(
                file,
                "f {} {} {} {}",
                noel[0] + 1,
                noel[1] + 1,
                noel[2] + 1,
                noel[3] + 1
            )?,
            _ => {
                unreachable!()
            }
        }
    }
    Ok(())
}

// ------------------------/

pub fn save_tri2xyz<Path, Real>(filepath: Path, tri2xyz: &[Real]) -> anyhow::Result<()>
where
    Path: AsRef<std::path::Path>,
    Real: num_traits::Float + std::fmt::Display,
{
    let file = File::create(filepath).context("file  not found.")?;
    let mut file = std::io::BufWriter::new(file);
    write_vtx2xyz(&mut file, tri2xyz, 3)?;
    // let num_vtx = vtx2xyz.len() / num_dim;
    let num_tri = tri2xyz.len() / 9;
    for i_tri in 0..num_tri {
        writeln!(
            file,
            "f {} {} {}",
            i_tri * 3 + 1,
            i_tri * 3 + 2,
            i_tri * 3 + 3
        )?;
    }
    Ok(())
}

// -------------------------
// below: private functions

fn parse_vertex(str_in: &str) -> (i32, i32, i32) {
    let snums: Vec<&str> = str_in.split('/').collect();
    let mut nums: [i32; 3] = [0, 0, 0];
    for i in 0..snums.len() {
        nums[i] = snums[i].parse::<i32>().unwrap_or(0);
    }
    (nums[0] - 1, nums[1] - 1, nums[2] - 1)
}

#[test]
fn test_parse_vertex() {
    assert_eq!(parse_vertex("1/2/3"), (0, 1, 2));
    assert_eq!(parse_vertex("1//3"), (0, -1, 2));
    assert_eq!(parse_vertex("1/2"), (0, 1, -1));
    assert_eq!(parse_vertex("1"), (0, -1, -1));
}