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use tracing::{error, instrument};
use crate::{Halfedge, HalfedgeId, MeshGraph, VertexId, error_none};
impl MeshGraph {
/// Inserts a pair of halfedges and connects them to the given vertices (from and to the halfedge) and each other as twins.
/// If the edge already exists or partially exists,
/// it returns the existing edge while creating any missing halfedges.
///
/// See also [`add_edge`].
#[instrument(skip(self))]
pub fn add_or_get_edge(
&mut self,
start_vertex_id: VertexId,
end_vertex_id: VertexId,
) -> Option<AddOrGetEdge> {
let ret = match self.add_or_get_edge_inner(start_vertex_id, end_vertex_id) {
Some(ret) => ret,
None => {
let start_to_end_he_id = self.add_halfedge(start_vertex_id, end_vertex_id)?;
let twin_he_id = self.add_halfedge(end_vertex_id, start_vertex_id)?;
AddOrGetEdge {
start_to_end_he_id,
twin_he_id,
new_start_to_end: true,
new_twin: true,
}
}
};
// insert_or_get_edge_inner ensures that both halfedges exist.
self.halfedges[ret.start_to_end_he_id].twin = Some(ret.twin_he_id);
self.halfedges[ret.twin_he_id].twin = Some(ret.start_to_end_he_id);
let start_v = self
.vertices
.get_mut(start_vertex_id)
.or_else(error_none!("Vertex not found"))?;
start_v.outgoing_halfedge = Some(ret.start_to_end_he_id);
let end_v = self
.vertices
.get_mut(end_vertex_id)
.or_else(error_none!("Vertex not found"))?;
end_v.outgoing_halfedge = Some(ret.twin_he_id);
Some(ret)
}
/// Adds or gets a boundary edge between two vertices.
/// If the edge already exists and the halfedge (start_vertex_id, end_vertex_id) is a boundary halfedge, it is returned;
/// otherwise, a new halfedge pair is created.
///
/// Note that this can lead to duplicate halfedges if the edge already exists but is not a boundary edge.
pub fn add_or_get_boundary_edge(
&mut self,
start_vertex_id: VertexId,
end_vertex_id: VertexId,
) -> Option<AddOrGetEdge> {
let existing_he_ids = self.halfedges_from_to(start_vertex_id, end_vertex_id);
if let Some(he_id) = existing_he_ids.into_iter().find(|he_id| {
// already checked in `halfedges_from_to()`
let he = &self.halfedges[*he_id];
he.is_boundary() && he.twin.is_some()
}) {
// already checked in `halfedges_from_to()`
let he = self.halfedges[he_id];
return Some(AddOrGetEdge {
start_to_end_he_id: he_id,
twin_he_id: he.twin.unwrap(), // checked above
new_start_to_end: false,
new_twin: false,
});
}
let AddEdge {
start_to_end_he_id,
twin_he_id,
} = self.add_edge(start_vertex_id, end_vertex_id)?;
Some(AddOrGetEdge {
start_to_end_he_id,
twin_he_id,
new_start_to_end: true,
new_twin: true,
})
}
fn add_or_get_edge_inner(
&mut self,
start_vertex_id: VertexId,
end_vertex_id: VertexId,
) -> Option<AddOrGetEdge> {
let mut he1_id = self.halfedge_from_to(start_vertex_id, end_vertex_id);
let mut he2_id = self.halfedge_from_to(end_vertex_id, start_vertex_id);
let mut new1 = false;
let mut new2 = false;
match (he1_id, he2_id) {
(Some(h1_id), Some(h2_id)) => {
let h1 = self
.halfedges
.get(h1_id)
.or_else(error_none!("Halfedge not found"))?;
let h2 = self
.halfedges
.get(h2_id)
.or_else(error_none!("Halfedge not found"))?;
if h1.twin != Some(h2_id) || h2.twin != Some(h1_id) {
error!("Halfedge twins are not consistent.");
}
}
(Some(_h1_id), None) => {
he2_id = Some(self.add_halfedge(end_vertex_id, start_vertex_id)?);
new2 = true;
}
(None, Some(_h2_id)) => {
he1_id = Some(self.add_halfedge(start_vertex_id, end_vertex_id)?);
new1 = true;
}
(None, None) => {
// the outer method will handle this case
return None;
}
}
// we just made sure that h1_id and h2_id are Some(_)
let start_to_end_he_id = he1_id.unwrap();
let twin_he_id = he2_id.unwrap();
Some(AddOrGetEdge {
start_to_end_he_id,
twin_he_id,
new_start_to_end: new1,
new_twin: new2,
})
}
/// Inserts a pair of halfedges and connects them to the given vertices (from and to the halfedge) and each other as twins.
/// This creates two halfedges wether the vertices already have an edge between them or not.
///
/// If you don't want this, consider using [`add_or_get_edge`] instead.
pub fn add_edge(&mut self, start_vertex: VertexId, end_vertex: VertexId) -> Option<AddEdge> {
let start_to_end_he_id = self.add_halfedge(start_vertex, end_vertex)?;
let twin_he_id = self.add_halfedge(end_vertex, start_vertex)?;
// Just inserted above
self.halfedges[start_to_end_he_id].twin = Some(twin_he_id);
self.halfedges[twin_he_id].twin = Some(start_to_end_he_id);
// Vertex existence already checked in `add_halfedge`
self.vertices[start_vertex].outgoing_halfedge = Some(start_to_end_he_id);
self.vertices[end_vertex].outgoing_halfedge = Some(twin_he_id);
Some(AddEdge {
start_to_end_he_id,
twin_he_id,
})
}
/// Inserts a halfedge into the mesh graph. It only connects the halfedge to the given end vertex but not the reverse.
/// It also doesn't do any other connections.
///
/// It does insert into `self.outgoing_halfedges`.
///
/// Use [`insert_or_get_edge`] instead of this when you can to lower the chance of creating an invalid graph.
#[instrument(skip(self))]
pub fn add_halfedge(
&mut self,
start_vertex: VertexId,
end_vertex: VertexId,
) -> Option<HalfedgeId> {
let halfedge = Halfedge {
end_vertex,
next: None,
twin: None,
face: None,
};
let he_id = self.halfedges.insert(halfedge);
self.outgoing_halfedges
.entry(start_vertex)
.or_else(error_none!("Start vertex not found {start_vertex:?}"))?
.or_default()
.push(he_id);
Some(he_id)
}
}
/// Return value of `add_or_get_edge`
pub struct AddOrGetEdge {
/// Id of the halfedge from start vertex to end vertex
pub start_to_end_he_id: HalfedgeId,
/// Id of the halfedge from end vertex to start vertex
pub twin_he_id: HalfedgeId,
/// Whether the halfedge from start vertex to end vertex was newly created
pub new_start_to_end: bool,
/// Whether the halfedge from end vertex to start vertex was newly created
pub new_twin: bool,
}
impl AddOrGetEdge {
/// Return the ids of the newly created halfedges
pub fn created_he_ids(&self) -> Vec<HalfedgeId> {
let mut he_ids = vec![];
if self.new_start_to_end {
he_ids.push(self.start_to_end_he_id);
}
if self.new_twin {
he_ids.push(self.twin_he_id);
}
he_ids
}
}
/// Return value of `add_edge`
pub struct AddEdge {
/// Id of the halfedge from start vertex to end vertex
pub start_to_end_he_id: HalfedgeId,
/// Id of the halfedge from end vertex to start vertex
pub twin_he_id: HalfedgeId,
}