feat(model): add section plane workflow

src/app/command_driver.rs

@@ -353,7 +353,32 @@ impl OpenCADStudio {
             self.reset_tracking_after_point();
             self.push_ucs_to_cmd(i);
         }
-        if let StepInput::EntityPick(handle, _) = &input {
+        if let StepInput::EntityPick(handle, point) = &input {
+            let solid_pick = matches!(
+                self.tabs[i].scene.document.get_entity(*handle),
+                Some(
+                    acadrust::EntityType::Solid3D(_)
+                        | acadrust::EntityType::Surface(_)
+                        | acadrust::EntityType::Region(_)
+                        | acadrust::EntityType::Body(_)
+                )
+            );
+            let direction = if solid_pick {
+                self.tabs[i]
+                    .scene
+                    .solid_planar_face_normal_at(*handle, *point)
+            } else {
+                self.tabs[i]
+                    .scene
+                    .document
+                    .get_entity(*handle)
+                    .and_then(crate::entities::curve::entity_curve)
+                    .and_then(|curve| curve.plane.normal())
+                    .map(glam::DVec3::from_array)
+            };
+            if let Some(command) = self.tabs[i].active_cmd.as_mut() {
+                command.set_entity_pick_direction(direction);
+            }
             if self.tabs[i].active_cmd.as_ref()
                 .is_some_and(|command| command.inject_before_entity_pick())
             {

src/app/commands/draw.rs

@@ -1212,6 +1212,64 @@ impl OpenCADStudio {
                 }
             }
 
+            "SECTIONPLANE" => {
+                use crate::modules::model::sectionplane_cmd::SectionPlaneCommand;
+                let (bounds, next_name) = {
+                    let scene = &mut self.tabs[i].scene;
+                    let solid_handles = scene
+                        .document
+                        .entities()
+                        .filter_map(|entity| {
+                            matches!(
+                                entity,
+                                acadrust::EntityType::Solid3D(_)
+                                    | acadrust::EntityType::Surface(_)
+                                    | acadrust::EntityType::Region(_)
+                                    | acadrust::EntityType::Body(_)
+                            )
+                            .then_some(entity.common().handle)
+                        })
+                        .collect::<Vec<_>>();
+                    scene.restore_solid_models(&solid_handles);
+                    let bounds = solid_handles
+                        .iter()
+                        .filter_map(|handle| scene.solid_models.get(handle))
+                        .filter_map(crate::scene::model::solid_model::extent)
+                        .fold(None::<(glam::DVec3, glam::DVec3)>, |bounds, (low, high)| {
+                            let low = glam::DVec3::from_array(low);
+                            let high = glam::DVec3::from_array(high);
+                            Some(match bounds {
+                                None => (low, high),
+                                Some((min, max)) => (min.min(low), max.max(high)),
+                            })
+                        });
+                    let next_name = scene
+                        .document
+                        .entities()
+                        .filter_map(|entity| {
+                            let acadrust::EntityType::Extended(extended) = entity else {
+                                return None;
+                            };
+                            let acadrust::entities::ExtendedEntityData::SectionObject(data) =
+                                &extended.data
+                            else {
+                                return None;
+                            };
+                            data.name
+                                .strip_prefix("Section Plane (")
+                                .and_then(|name| name.strip_suffix(')'))
+                                .and_then(|name| name.parse::<usize>().ok())
+                        })
+                        .max()
+                        .unwrap_or(0)
+                        + 1;
+                    (bounds, next_name)
+                };
+                let command = SectionPlaneCommand::new(bounds, next_name);
+                self.command_line.push_info(&command.prompt());
+                self.tabs[i].active_cmd = Some(Box::new(command));
+            }
+
             // 3DALIGN <18 numbers> — align the selected solid by 3 source→3 dest points.
             cmd if cmd == "3DALIGN"
                 || cmd == "ALIGN3D"

src/app/commands/mod.rs

@@ -462,6 +462,7 @@ inventory::submit!(crate::command::CommandRegistration {
         "3DALIGN",
         "ALIGN3D",
         "SECTION",
+        "SECTIONPLANE",
         "PYRAMID",
         "PYR",
         "SPLINEFIT",

src/app/control/actions.rs

@@ -171,6 +171,7 @@ impl OpenCADStudio {
                         | "text_color"
                         | "block_content_color"
                         | "background_fill_color"
+                        | "indicator_fill_color"
                 ) {
                     self.update(Message::PropColorFieldChanged {
                         field: p.field.into(),

src/app/update/mod.rs

@@ -5226,6 +5226,21 @@ impl OpenCADStudio {
             Message::PropColorFieldChanged { field, color } => {
                 let i = self.active_tab;
                 let handles = self.property_target_handles(i);
+                if field == "indicator_fill_color" {
+                    self.apply_property_op(i, "CHPROP", &handles, |app, handle| {
+                        if let Some(acadrust::EntityType::Extended(extended)) =
+                            app.tabs[i].scene.document.get_entity_mut(handle)
+                        {
+                            if let acadrust::entities::ExtendedEntityData::SectionObject(data) =
+                                &mut extended.data
+                            {
+                                data.indicator_color = color;
+                            }
+                        }
+                    });
+                    self.tabs[i].properties.open_color_field = None;
+                    return Task::none();
+                }
                 // Dim-line colour override (Leader / Dimension): write it as an
                 // ACAD_DSTYLE code-176 override (an ACI index) so it round-trips
                 // through DWG and DXF. RGB picks collapse to the nearest ACI, in