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fix(area): measure the curve, not a polygon through some of its points

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A hatch's area was not the area of anything. Its boundary was flattened
into a ring by pushing an arc's *centre* into it, and a spline's control
points — neither of which is on the boundary — and the shoelace formula
was run over the result. Boundary edges now go through the kernel, which
measures each for what it encloses: an arc contributes its sector, a
spline is integrated.

AREA had three measurements between them. The bulged-polyline one
carried its own arc corrections; the planar entities it did not cover
fell through to mass properties. Both are now one call on the entity's
curve, which gets the bulges, the ellipse and the spline right in the
same place. What is left is the genuinely spatial — a 3D polyline, a
spline whose points wander off any plane — measured as rings of points
by Newell's method rather than by projecting them flat.

Regions were doing the same Newell sum by hand. They share it now.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
Hakan Seven 2026-08-09 01:44:04 +03:00
commit 77a9167e34
4 changed files with 168 additions and 141 deletions
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34
src/entities/solid3d.rs
View file

@ -7,6 +7,7 @@
// the MeshModel vertices to match.
use acadrust::entities::{Body, Region, Solid3D, Surface};
use acadrust::kernel::space::polygon;
use crate::t;
use crate::command::EntityTransform;
use crate::entities::common::{center_grip, edit_prop as edit, parse_f64, ro_prop as ro};
@ -203,30 +204,25 @@ fn position_section(prefix: &str, p: &acadrust::types::Vector3) -> PropSection {
/// holes subtract) and halves its magnitude — exact for a single planar
/// loop, approximate for multi-loop or curved regions. Returns zeros when
/// there is nothing to measure.
/// The area and perimeter of a region's boundary wires.
///
/// Measured in space rather than in projection: a region need not lie in a
/// coordinate plane, and flattening it to XY first would report its shadow.
fn region_area_perimeter(wires: &[acadrust::entities::Wire]) -> (f64, f64) {
let mut area_vector = [0.0f64; 3];
let mut perimeter = 0.0;
let (mut nx, mut ny, mut nz) = (0.0, 0.0, 0.0);
for wire in wires {
let pts = &wire.points;
if pts.len() < 2 {
continue;
}
for seg in pts.windows(2) {
let dx = seg[1].x - seg[0].x;
let dy = seg[1].y - seg[0].y;
let dz = seg[1].z - seg[0].z;
perimeter += (dx * dx + dy * dy + dz * dz).sqrt();
}
let n = pts.len();
for i in 0..n {
let a = &pts[i];
let b = &pts[(i + 1) % n];
nx += (a.y - b.y) * (a.z + b.z);
ny += (a.z - b.z) * (a.x + b.x);
nz += (a.x - b.x) * (a.y + b.y);
let ring: Vec<[f64; 3]> = wire.points.iter().map(|p| [p.x, p.y, p.z]).collect();
// Wires arrive as open chains that the region closes between them, so
// the length is the chain's and the area vectors are summed before
// being measured — one wire's contribution is not an area on its own.
perimeter += polygon::chain_length(&ring);
let piece = polygon::area_vector(&ring);
for axis in 0..3 {
area_vector[axis] += piece[axis];
}
}
let area = 0.5 * (nx * nx + ny * ny + nz * nz).sqrt();
let area = (area_vector[0].powi(2) + area_vector[1].powi(2) + area_vector[2].powi(2)).sqrt();
(area, perimeter)
}