axiolid_measure/
mesh_measure.rs

1//! The reference [`Measure`] provider for triangle meshes.
2//!
3//! # Why this exists
4//!
5//! `Measure<T>` was a trait with no implementor, and `MassProperties` a struct
6//! nothing produced. The parts were all present -- area, volume and centroid
7//! were computed by free functions in [`crate::mesh`] -- but nothing assembled
8//! them into the declared contract, and `second_moment_diagonal` was never
9//! computed at all.
10//!
11//! # Refusal over a plausible number
12//!
13//! Mass properties are only defined for a closed oriented solid. An open shell
14//! has a surface area but no enclosed volume, so this provider refuses it
15//! rather than reporting the divergence sum of an open surface, which is a
16//! finite number with no meaning.
17
18use axiolid_core::Tolerance;
19use axiolid_mesh::TriMesh;
20
21use crate::{
22    mesh::{second_moments, surface_properties, volume_properties},
23    MassProperties, Measure, MeshMeasureError,
24};
25
26/// Reference mass-property provider for triangle meshes.
27///
28/// Deterministic: the sums run in triangle order, so the result is
29/// reproducible for a given mesh.
30#[derive(Debug, Default, Clone, Copy)]
31pub struct MeshMeasure;
32
33impl Measure<TriMesh> for MeshMeasure {
34    type Error = MeshMeasureError;
35
36    /// Area, signed volume, volume centroid and second moments in one pass.
37    ///
38    /// The centroid reported is the VOLUME centroid, not the area centroid:
39    /// for mass properties of a solid that is the meaningful one, and
40    /// [`surface_properties`] still exposes the area centroid separately for
41    /// callers measuring a shell.
42    fn measure(
43        &self,
44        value: &TriMesh,
45        tolerance: Tolerance,
46    ) -> Result<MassProperties, Self::Error> {
47        // Volume first: it is the strictest admission (closed two-manifold),
48        // so an unusable mesh is refused before any further work.
49        let volume = volume_properties(value, tolerance)?;
50        let surface = surface_properties(value, tolerance)?;
51        let second_moment_diagonal = second_moments(value, tolerance)?;
52        Ok(MassProperties {
53            area: surface.area,
54            signed_volume: volume.signed_volume,
55            centroid: volume.centroid,
56            second_moment_diagonal,
57        })
58    }
59}
axiolid_measure/mesh_measure.rs

axiolid_measure/
mesh_measure.rs
