ncollide3d/procedural/path/
polyline_pattern.rs

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use crate::procedural::path::{CurveSampler, PathSample, StrokePattern};
use crate::procedural::trimesh::{IndexBuffer, TriMesh};
use crate::procedural::utils;
use na::{self, Isometry3, Point2, Point3, RealField, Vector3};

/// A pattern composed of polyline and two caps.
pub struct PolylinePattern<N: RealField + Copy, C1, C2> {
    pattern: Vec<Point3<N>>,
    closed: bool,
    last_start_id: u32,
    start_cap: C1,
    end_cap: C2,
}

/// Trait to be implemented by caps compatible with a `PolylinePattern`.
pub trait PolylineCompatibleCap<N: RealField + Copy> {
    /// Generates the mesh for the cap at the beginning of a path.
    fn gen_start_cap(
        &self,
        attach_id: u32,
        pattern: &[Point3<N>],
        pt: &Point3<N>,
        dir: &Vector3<N>,
        closed: bool,
        coords: &mut Vec<Point3<N>>,
        indices: &mut Vec<Point3<u32>>,
    );

    /// Generates the mesh for the cap at the end of a path.
    fn gen_end_cap(
        &self,
        attach_id: u32,
        pattern: &[Point3<N>],
        pt: &Point3<N>,
        dir: &Vector3<N>,
        closed: bool,
        coords: &mut Vec<Point3<N>>,
        indices: &mut Vec<Point3<u32>>,
    );
}

impl<N, C1, C2> PolylinePattern<N, C1, C2>
where
    N: RealField + Copy,
    C1: PolylineCompatibleCap<N>,
    C2: PolylineCompatibleCap<N>,
{
    /// Creates a new polyline pattern.
    pub fn new(
        pattern: &[Point2<N>],
        closed: bool,
        start_cap: C1,
        end_cap: C2,
    ) -> PolylinePattern<N, C1, C2> {
        let mut coords3d = Vec::with_capacity(pattern.len());

        for v in pattern.iter() {
            coords3d.push(Point3::new(v.x.clone(), v.y.clone(), na::zero()));
        }

        PolylinePattern {
            pattern: coords3d,
            closed: closed,
            last_start_id: 0,
            start_cap: start_cap,
            end_cap: end_cap,
        }
    }
}

impl<N, C1, C2> StrokePattern<N> for PolylinePattern<N, C1, C2>
where
    N: RealField + Copy,
    C1: PolylineCompatibleCap<N>,
    C2: PolylineCompatibleCap<N>,
{
    fn stroke<C: CurveSampler<N>>(&mut self, sampler: &mut C) -> TriMesh<N> {
        let mut vertices = Vec::new();
        let mut indices = Vec::new();
        let npts = self.pattern.len() as u32;
        // FIXME: collect the normals too.
        // let mut normals  = Vec::new();

        loop {
            let next = sampler.next();

            // second match to add the inner triangles.
            match next {
                PathSample::StartPoint(ref pt, ref dir)
                | PathSample::InnerPoint(ref pt, ref dir)
                | PathSample::EndPoint(ref pt, ref dir) => {
                    let mut new_polyline = self.pattern.clone();
                    let transform;

                    if dir.x.is_zero() && dir.z.is_zero() {
                        // FIXME: this might not be enough to avoid singularities.
                        transform = Isometry3::face_towards(pt, &(*pt + *dir), &Vector3::x());
                    } else {
                        transform = Isometry3::face_towards(pt, &(*pt + *dir), &Vector3::y());
                    }

                    for p in &mut new_polyline {
                        *p = transform * &*p;
                    }

                    let new_start_id = vertices.len() as u32;

                    vertices.extend(new_polyline.into_iter());

                    if new_start_id != 0 {
                        if self.closed {
                            utils::push_ring_indices(
                                new_start_id,
                                self.last_start_id,
                                npts,
                                &mut indices,
                            );
                        } else {
                            utils::push_open_ring_indices(
                                new_start_id,
                                self.last_start_id,
                                npts,
                                &mut indices,
                            );
                        }

                        self.last_start_id = new_start_id;
                    }
                }
                PathSample::EndOfSample => {
                    return TriMesh::new(vertices, None, None, Some(IndexBuffer::Unified(indices)))
                }
            }

            // third match to add the end cap
            // FIXME: this will fail with patterns having multiple starting and end points!
            match next {
                PathSample::StartPoint(ref pt, ref dir) => {
                    self.start_cap.gen_start_cap(
                        0,
                        &self.pattern,
                        pt,
                        dir,
                        self.closed,
                        &mut vertices,
                        &mut indices,
                    );
                }
                PathSample::EndPoint(ref pt, ref dir) => {
                    self.end_cap.gen_end_cap(
                        vertices.len() as u32 - npts,
                        &self.pattern,
                        pt,
                        dir,
                        self.closed,
                        &mut vertices,
                        &mut indices,
                    );
                }
                _ => {}
            }
        }
    }
}