H. Conrad
63accec16e
A scale across a revolution's axis keeps the face a surface of revolution and is written as one; any other refusal from the writer is an export error, not a panic.
104 lines
4.4 KiB
Rust
104 lines
4.4 KiB
Rust
use truck_modeling as mt;
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use truck_stepio::out;
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use crate::body::Body;
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use crate::{KernelError, Result, guard};
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/// Intersection-curve edges (from booleans) as cubic B-splines through the exact curve: STEP
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/// readers get plain 3D geometry that lies on both faces, and the file does not repeat the two
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/// surfaces for every such edge.
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fn plain_curves(b: &Body) -> Result<mt::Solid> {
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let s = crate::ops::placed_topology(&b.solid, mt::Matrix4::from_scale(1.0))?;
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let size = b.size();
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let mut seen = std::collections::HashSet::new();
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for e in s.edge_iter() {
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if !seen.insert(e.id()) {
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continue;
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}
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if let mt::Curve::IntersectionCurve(ic) = e.curve()
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&& let Some(c) = hermite_through(&ic, size * 1e-4)
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{
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e.set_curve(mt::Curve::BSplineCurve(c));
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}
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}
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Ok(s)
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}
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/// A C¹ cubic B-spline through exact points of `c` spaced so that chords deviate at most `tol`
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/// (Catmull–Rom tangents over chord length; the cubic is far closer than the chords).
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fn hermite_through<C>(c: &C, tol: f64) -> Option<mt::BSplineCurve<mt::Point3>>
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where
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C: mt::ParametricCurve<Point = mt::Point3, Vector = mt::Vector3> + mt::BoundedCurve + mt::ParameterDivision1D<Point = mt::Point3>,
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{
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use mt::{InnerSpace, MetricSpace};
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let (_, pts) = c.parameter_division(c.range_tuple(), tol);
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let pts: Vec<mt::Point3> = pts.into_iter().fold(Vec::new(), |mut v: Vec<mt::Point3>, p| {
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if v.last().is_none_or(|q| q.distance(p) > tol * 1e-3) {
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v.push(p);
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}
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v
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});
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let n = pts.len().checked_sub(1).filter(|n| *n >= 1 && *n < 1_000_000)?;
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let mut u = vec![0.0; n + 1];
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for i in 1..=n {
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u[i] = u[i - 1] + pts[i].distance(pts[i - 1]);
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}
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let tangent = |i: usize| {
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let (a, b) = (i.saturating_sub(1), (i + 1).min(n));
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(pts[b] - pts[a]) / (u[b] - u[a])
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};
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let mut ctrl = vec![pts[0]];
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let mut knots = vec![u[0]; 4];
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for i in 0..n {
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let h = u[i + 1] - u[i];
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ctrl.push(pts[i] + tangent(i) * (h / 3.0));
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ctrl.push(pts[i + 1] - tangent(i + 1) * (h / 3.0));
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ctrl.push(pts[i + 1]);
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knots.extend(std::iter::repeat_n(u[i + 1], if i + 1 == n { 4 } else { 3 }));
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}
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if ctrl.iter().any(|p| !(p.x.is_finite() && p.y.is_finite() && p.z.is_finite())) || tangent(0).magnitude() == 0.0 {
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return None;
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}
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mt::BSplineCurve::try_new(mt::KnotVec::from(knots), ctrl).ok()
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}
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/// truck's STEP text for the given bodies (geometry and topology; product data is ours).
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pub(crate) fn truck_step(bodies: &[&Body], system: &str) -> Result<String> {
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if bodies.is_empty() {
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return Err(KernelError::Invalid("nothing to export".into()));
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}
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for b in bodies {
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b.require_brep("STEP export")?;
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}
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guard("step export", || {
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let cs: Vec<_> = bodies.iter().map(|b| plain_curves(b).map(|solid| solid.compress())).collect::<Result<_>>()?;
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let models: out::StepModels<_, _, _> = cs.iter().collect();
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let header = out::StepHeaderDescriptor { organization_system: system.to_owned(), ..Default::default() };
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written(&out::CompleteStepDisplay::new(models, header))
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})
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}
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/// The text of truck's STEP writer, or an error. The writer refuses some geometry by returning
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/// `fmt::Error` after a line saying why; `to_string` would turn that into a panic (caught by
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/// `guard` on the desktop, but the browser build aborts on any panic).
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fn written(display: &impl std::fmt::Display) -> Result<String> {
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use std::fmt::Write;
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let mut text = String::new();
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match write!(text, "{display}") {
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Ok(()) => Ok(text),
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Err(_) => {
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let why = text.lines().last().map(str::trim).filter(|l| !l.is_empty() && !l.starts_with('#')).unwrap_or("unsupported geometry");
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Err(KernelError::Failed(format!("not supported yet: STEP export of this body ({why})")))
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}
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}
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}
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/// STEP (ISO 10303-21, AP242) text for the given bodies as one part (`Body1`…, with the
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/// bodies' colours).
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pub fn step_export(bodies: &[&Body], system: &str) -> Result<String> {
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let list: Vec<crate::ExportBody> =
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bodies.iter().enumerate().map(|(i, b)| crate::ExportBody { name: format!("Body{}", i + 1), body: b, color: b.color() }).collect();
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let header = crate::StepHeader { organization: system.to_string(), ..Default::default() };
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crate::step_out::step_export_bodies(&list, &header)
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}
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