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//! Face approximation
//!
//! See [`FaceApprox`].
use std::{collections::BTreeSet, ops::Deref};
use fj_interop::mesh::Color;
use crate::{
objects::{Face, FaceSet, Handedness},
validate::ValidationConfig,
};
use super::{
cycle::CycleApprox, edge::EdgeCache, Approx, ApproxPoint, Tolerance,
};
impl Approx for &FaceSet {
type Approximation = BTreeSet<FaceApprox>;
type Cache = EdgeCache;
fn approx_with_cache(
self,
tolerance: impl Into<Tolerance>,
cache: &mut Self::Cache,
) -> Self::Approximation {
let tolerance = tolerance.into();
let approx = self
.into_iter()
.map(|face| face.approx_with_cache(tolerance, cache))
.collect();
let min_distance = ValidationConfig::default().distinct_min_distance;
let mut all_points: BTreeSet<ApproxPoint<2>> = BTreeSet::new();
// Run some validation code on the approximation.
for approx in &approx {
let approx: &FaceApprox = approx;
for a in &approx.points() {
for b in &all_points {
let distance = (b.global_form - a.global_form).magnitude();
if b.global_form != a.global_form && distance < min_distance
{
panic!(
"Invalid approximation: \
Distinct points are too close \
(a: {:?}, b: {:?}, distance: {distance})",
a.global_form, b.global_form,
);
}
}
all_points.insert(a.clone());
}
}
approx
}
}
impl Approx for &Face {
type Approximation = FaceApprox;
type Cache = EdgeCache;
fn approx_with_cache(
self,
tolerance: impl Into<Tolerance>,
cache: &mut Self::Cache,
) -> Self::Approximation {
let tolerance = tolerance.into();
// Curved faces whose curvature is not fully defined by their edges
// are not supported yet. For that reason, we can fully ignore `face`'s
// `surface` field and just pass the edges to `Self::for_edges`.
//
// An example of a curved face that is supported, is the cylinder. Its
// curvature is fully defined be the edges (circles) that border it. The
// circle approximations are sufficient to triangulate the surface.
//
// An example of a curved face that is currently not supported, and thus
// doesn't need to be handled here, is a sphere. A spherical face would
// would need to provide its own approximation, as the edges that bound
// it have nothing to do with its curvature.
let exterior = (self.exterior().deref(), self.surface().deref())
.approx_with_cache(tolerance, cache);
let mut interiors = BTreeSet::new();
for cycle in self.interiors() {
let cycle = (cycle.deref(), self.surface().deref())
.approx_with_cache(tolerance, cache);
interiors.insert(cycle);
}
FaceApprox {
exterior,
interiors,
color: self.color(),
coord_handedness: self.coord_handedness(),
}
}
}
/// An approximation of a [`Face`]
#[derive(Debug, Eq, PartialEq, Ord, PartialOrd)]
pub struct FaceApprox {
/// Approximation of the exterior cycle
pub exterior: CycleApprox,
/// Approximations of the interior cycles
pub interiors: BTreeSet<CycleApprox>,
/// The color of the approximated face
pub color: Option<Color>,
/// The handedness of the approximated face's front-side coordinate system
pub coord_handedness: Handedness,
}
impl FaceApprox {
/// Compute all points that make up the approximation
pub fn points(&self) -> BTreeSet<ApproxPoint<2>> {
let mut points = BTreeSet::new();
points.extend(self.exterior.points());
for cycle_approx in &self.interiors {
points.extend(cycle_approx.points());
}
points
}
}