Module plexus::geometry::compose

Higher order geometric traits.

This module defines higher order traits for operations on a graph. It also provides aliases for geometric types to improve readability of type constraints. These traits can be used as contraints to prove to the compiler that certain operations are supported without specifying complicated relationships.

The traits in this module have blanket implementations that apply when certain geometric and operational traits are implemented. For example, if a type implements AsPosition and the Output type of that implementation also implements Cross and Normalize, then a Geometry using that type as its Vertex attribute will likely implement the FaceNormal trait in this module.

Examples

A function that subdivides faces in a graph by splitting edges at their midpoints:

use plexus::geometry::alias::VertexPosition;
use plexus::geometry::compose::EdgeMidpoint;
use plexus::geometry::convert::AsPosition;
use plexus::geometry::Geometry;
use plexus::graph::{FaceView, MeshGraph};
use plexus::prelude::*;
use smallvec::SmallVec;

// Requires `EdgeMidpoint` for `split_at_midpoint`.
pub fn circumscribe<G>(face: FaceView<&mut MeshGraph<G>, G>) -> FaceView<&mut MeshGraph<G>, G>
where
    G: EdgeMidpoint<Midpoint = VertexPosition<G>> + Geometry,
    G::Vertex: AsPosition,
{
    let arity = face.arity();
    let mut arc = face.into_arc();
    let mut splits = SmallVec::<[_; 4]>::with_capacity(arity);
    for _ in 0..arity {
        let vertex = arc.split_at_midpoint();
        splits.push(vertex.key());
        arc = vertex.into_outgoing_arc().into_next_arc();
    }
    let mut face = arc.into_face().unwrap();
    for (a, b) in splits.into_iter().perimeter() {
        face = face.split(ByKey(a), ByKey(b)).unwrap().into_face().unwrap();
    }
    face
}

Traits

ArcNormal
EdgeMidpoint
FaceCentroid
FaceNormal