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/*
Copyright 2017 Martin Buck
This file is part of rust-3d.
rust-3d is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
rust-3d is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with rust-3d. If not, see <http://www.gnu.org/licenses/>.
*/
//! HalfEdge, the half edge data structure
use prelude::*;
use utils::safe_append_at;
#[derive (Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
/// Edge type used within the HalfEdge
struct Edge {
tail: VId,
twin: Option<EId>
}
#[derive (Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
/// HalfEdge, the half edge data structure
pub struct HalfEdge {
edges: Vec<Edge>,
vertices_start_edges: Vec<Vec<EId>> //@todo better name
}
impl HalfEdge {
/// Creates a new HalfEdge3D for the given IsMesh3D
/// This only stays valid if IMesh3D is not changed after creation
/// The mesh must be manifold (@todo ensure via types?)
pub fn new<T, M>(mesh: &M) -> Self where
M: IsMesh<T, Face3> {
let n_faces = mesh.num_faces();
let mut edges = Vec::with_capacity(3 * n_faces);
let mut vertices_start_edges = Vec::new();
for i in 0..n_faces {
match mesh.face_vertex_ids(FId{val: i}) {
Err(_) => {},
Ok(face) => {
edges.push(Edge{tail: face.a, twin: None});
edges.push(Edge{tail: face.b, twin: None});
edges.push(Edge{tail: face.c, twin: None});
safe_append_at(&mut vertices_start_edges, face.a.val, EId{val: i*3 + 0});
safe_append_at(&mut vertices_start_edges, face.b.val, EId{val: i*3 + 1});
safe_append_at(&mut vertices_start_edges, face.c.val, EId{val: i*3 + 2});
}
}
}
let mut result = HalfEdge{edges: edges , vertices_start_edges: vertices_start_edges };
// For each edge, get tail of next
// Of this get all edges originating
// Of these the one where next has the same tail must be the twin
// @todo could let this fail if there is more than one valid candidate (not manifold)
for i in 0..result.edges.len() {
let _ = result.next(EId{val: i})
.and_then(|next_id| result.edges_originating(result.edges[next_id.val].tail))
.map(|originating_ids| for originating_id in originating_ids {
let _ = result.next(originating_id)
.map(|candidate_id| if result.edges[candidate_id.val].tail == result.edges[i].tail {
result.edges[i].twin = Some(candidate_id)
});
});
}
result
}
/// Returns the ID of the vertex the edge originates from (error if id out of bounds)
pub fn tail(&self, id: EId) -> Result<VId> {
self.ensure_edge_id(id)?;
Ok(self.edges[id.val].tail)
}
/// Returns the ID of the face the edge belongs to (error if id out of bounds)
pub fn face(&self, id: EId) -> Result<FId> {
self.ensure_edge_id(id)?;
Ok(FId{val: id.val / 3})
}
/// Returns the ID of the twin edge (None if there isn't any) (error if id out of bounds)
pub fn twin(&self, id: EId) -> Result<Option<EId>> {
self.ensure_edge_id(id)?;
Ok(self.edges[id.val].twin.clone())
}
/// Returns the ID of the edge after this edge (error if id out of bounds)
pub fn next(&self, id: EId) -> Result<EId> {
self.ensure_edge_id(id)?;
if Self::last_in_face(id) {
return Ok(EId{val: id.val - 2});
}
Ok(EId{val: id.val + 1})
}
/// Returns the ID of the edge before this edge (error if id out of bounds)
pub fn prev(&self, id: EId) -> Result<EId> {
self.ensure_edge_id(id)?;
if Self::first_in_face(id) {
return Ok(EId{val: id.val + 2});
}
Ok(EId{val: id.val - 1})
}
/// Returns all edges originating (pointing away) from the given vertex (error if id out of bounds)
pub fn edges_originating(&self, id: VId) -> Result<Vec<EId>> {
self.ensure_vertex_id(id)?;
Ok(self.vertices_start_edges[id.val].clone())
}
/// Returns all edges ending (pointing at) the given vertex (error if id out of bounds)
pub fn edges_ending(&self, id: VId) -> Result<Vec<EId>> {
let originatings = self.edges_originating(id)?;
let mut result = Vec::with_capacity(originatings.len());
for edge in originatings {
match self.prev(edge) {
Err(_) => {},
Ok(id) => result.push(id)
}
}
Ok(result)
}
/// Returns all edges connected to the vertex (both originating and ending) (error if id out of bounds)
pub fn edges_all(&self, id: VId) -> Result<Vec<EId>> {
let originatings = self.edges_originating(id)?;
let mut result = Vec::with_capacity(originatings.len());
for edge in originatings {
result.push(edge);
match self.prev(edge) {
Err(_) => {},
Ok(id) => result.push(id)
}
}
Ok(result)
}
/// Returns all faces a vertex is part of (error if id out of bounds)
pub fn faces(&self, id: VId) -> Result<Vec<FId>> {
let originatings = self.edges_originating(id)?;
let mut result = Vec::with_capacity(originatings.len());
for edge in originatings {
match self.face(edge) {
Err(_) => {}
Ok(id) => result.push(id)
}
}
Ok(result)
}
/// Returns true if the give edge is the first within a face
fn first_in_face(id: EId) -> bool {
id.val % 3 == 0
}
/// Returns true if the give edge is the last within a face
fn last_in_face(id: EId) -> bool {
id.val % 3 == 2
}
/// Fails if the edge ID is out of bounds
pub fn ensure_edge_id(&self, id: EId) -> Result<()> {
if id.val >= self.edges.len() {
return Err(ErrorKind::IncorrectEdgeID);
}
Ok(())
}
/// Fails if the vertex ID is out of bounds
pub fn ensure_vertex_id(&self, id: VId) -> Result<()> {
if id.val >= self.vertices_start_edges.len() {
return Err(ErrorKind::IncorrectVertexID);
}
Ok(())
}
}