feat(model): add exact solid modelling tools

src/scene/convert/acis_export.rs

@@ -3,12 +3,21 @@
 //! Analytic surfaces remain analytic instead of becoming facets.
 
 use cadkernel::acis::append;
-use acadrust::entities::acis::SatDocument;
+use acadrust::entities::acis::{SabReader, SabWriter, SatDocument};
 use cadkernel::brep::Body;
 
 /// Returns `None` when the body contains an unsupported record form.
-pub fn planar_solid_to_sat(body: &Body) -> Option<SatDocument> {
+pub fn solid_to_sat(body: &Body) -> Option<SatDocument> {
     let mut document = SatDocument::new();
     append(body, &mut document).ok()?;
-    Some(document)
+    let document = SatDocument::parse(&document.to_sat_string()).ok()?;
+    let valid = |candidate: &SatDocument| {
+        let (restored, loss) = cadkernel::acis::lift(candidate);
+        loss.is_empty() && restored.len() == 1 && restored[0].validate().is_empty()
+    };
+    if !valid(&document) {
+        return None;
+    }
+    let binary = SabWriter::write(&document);
+    valid(&SabReader::read(&binary).ok()?).then_some(document)
 }