Complete UNION command behavior

src/scene/convert/solid3d_tess.rs

@@ -163,6 +163,10 @@ pub fn kernel_surface_body(surface: &Surface) -> Option<KernelBody> {
     kernel_acis_body(&surface.acis_data)
 }
 
+pub fn kernel_region_body(region: &Region) -> Option<KernelBody> {
+    kernel_acis_body(&region.acis_data)
+}
+
 fn kernel_acis_body(acis: &acadrust::entities::AcisData) -> Option<KernelBody> {
     let sat = parse_acis(
         || acis.parse(),

src/scene/entity.rs

@@ -605,6 +605,9 @@ impl Scene {
                     Some(EntityType::Surface(surface)) => {
                         crate::scene::convert::solid3d_tess::kernel_surface_body(surface)
                     }
+                    Some(EntityType::Region(region)) => {
+                        crate::scene::convert::solid3d_tess::kernel_region_body(region)
+                    }
                     _ => None,
                 })?;
                 Some((handle, body))

src/scene/model/solid_history.rs

@@ -975,6 +975,41 @@ fn cone_properties(
     ]
 }
 
+fn brep_properties(
+    document: &acadrust::CadDocument,
+    handle: acadrust::Handle,
+) -> Vec<PropSection> {
+    let (record_history, object_show_history, show_history_mode) =
+        history_flags(document, handle).unwrap_or((false, false, 1));
+    let (show_history, show_history_editable) =
+        displayed_history_state(object_show_history, show_history_mode);
+    vec![PropSection {
+        title: t!("Solid History").into_owned(),
+        props: vec![
+            Property {
+                label: t!("History").into_owned(),
+                field: PROP_HISTORY,
+                value: PropValue::Choice {
+                    selected: if record_history { "Record" } else { "None" }.to_string(),
+                    options: vec!["None".to_string(), "Record".to_string()],
+                },
+            },
+            Property {
+                label: t!("Show History").into_owned(),
+                field: PROP_SHOW_HISTORY,
+                value: if show_history_editable {
+                    PropValue::Choice {
+                        selected: if show_history { "Yes" } else { "No" }.to_string(),
+                        options: vec!["No".to_string(), "Yes".to_string()],
+                    }
+                } else {
+                    PropValue::ReadOnly(if show_history { "Yes" } else { "No" }.to_string())
+                },
+            },
+        ],
+    }]
+}
+
 fn cylinder_properties(
     document: &acadrust::CadDocument,
     handle: acadrust::Handle,
@@ -1411,6 +1446,7 @@ pub fn primitive_properties(
             extrusion_properties(document, handle, value)
         }
         SolidHistoryOperation::Revolve(value) => revolve_properties(document, handle, value),
+        SolidHistoryOperation::Brep(_) => brep_properties(document, handle),
         _ => Vec::new(),
     }
 }

src/scene/model/solid_model.rs

@@ -365,13 +365,18 @@ pub enum Bool {
 /// missing, and passing that on unchanged is the point: a half-done boolean
 /// looks finished.
 pub fn boolean(op: Bool, a: &Body, b: &Body) -> Option<Body> {
+    boolean_result(op, a, b).ok()
+}
+
+/// Combine two solids while retaining the kernel's exact refusal reason.
+pub fn boolean_result(op: Bool, a: &Body, b: &Body) -> Result<Body, brep::Snag> {
     let how = match op {
         Bool::Union => brep::Operation::Union,
         Bool::Subtract => brep::Operation::Difference,
         Bool::Intersect => brep::Operation::Intersection,
     };
     let tolerance = brep::operation_tolerance(&[a, b]);
-    brep::combine(a.clone(), b.clone(), how, tolerance).ok()
+    brep::combine(a.clone(), b.clone(), how, tolerance)
 }
 
 // ── Tessellation ────────────────────────────────────────────────────────────