fix: UCS FACE/OBJECT pick from the interactive prompt; reuse ocs_axes

Follow-up to #1341:
- interactive UCS offers Face / OBject; bare UCS OBJECT starts an entity pick
- one UcsPickCommand serves both FACE and OBJECT
- ucs_from_normal calls the existing arbitrary-axis helper instead of a copy
- prompt catalogue key and en-US text follow the new option list

Co-Authored-By: Claude Fable 5.1 <[email protected]>

locales/en-US/opencadstudio.ftl

@@ -4198,7 +4198,7 @@ view =
     .cmd-not-yet-implemented = __ocs_fmt_0__: not yet implemented.
     .viewport-s-in-layout = __ocs_fmt_0__ viewport(s) in layout "__ocs_fmt_1__":
 
-    .ucs-option-world-view-3point-z-x-y-origin-save-delete-or-name = UCS  option [World/View/3Point/Z/X/Y/Origin/Save/Delete] or name:
+    .ucs-option-world-view-3point-z-x-y-origin-save-delete-or-name = UCS  option [Face/OBject/World/View/3Point/Z/X/Y/Origin/Save/Delete] or name:
     .ucs-specify-new-origin = UCS  specify new origin:
     .ucs-specify-point-on-positive-x-axis = UCS  specify point on positive X axis:
     .ucs-specify-point-in-positive-xy-plane = UCS  specify point in positive XY plane:

src/app/commands/layerprops.rs

@@ -338,7 +338,7 @@ impl OpenCADStudio {
                             // surface point, so both entry points share the
                             // plane construction below.
                             None => {
-                                let picker = crate::command::UcsFaceCommand;
+                                let picker = crate::command::UcsPickCommand { face: true };
                                 self.command_line.push_info(&picker.prompt());
                                 self.tabs[i].active_cmd = Some(Box::new(picker));
                             }
@@ -386,9 +386,13 @@ impl OpenCADStudio {
                             })
                             .map(acadrust::Handle::new);
                         match target {
-                            None => self
-                                .command_line
-                                .push_error(crate::t!("Usage: UCS OBJECT <handle>").as_ref()),
+                            // Bare `UCS OBJECT` starts the pick; the click
+                            // comes back through this arm with the handle.
+                            None => {
+                                let picker = crate::command::UcsPickCommand { face: false };
+                                self.command_line.push_info(&picker.prompt());
+                                self.tabs[i].active_cmd = Some(Box::new(picker));
+                            }
                             Some(handle) => {
                                 let built = self.tabs[i]
                                     .scene

src/app/commands/mod.rs

@@ -739,9 +739,10 @@ inventory::submit!(crate::command::CommandRegistration {
         "SELSIM",
         // Draw a new object of the same type as the selected one. (#239)
         "ADDSELECTED",
+        // Outline of origin planes, open sketch and solid bodies.
+        "BROWSER",
         // Open and close a sketch: a drawing plane, a square-on view and
         // snapping, held together until the profile is done.
-        "BROWSER",
         "CREATESKETCH",
         "FINISHSKETCH",
         "SHEETSET",

src/app/helpers.rs

@@ -249,35 +249,20 @@ pub(super) fn ucs_z_axis(ucs: &Ucs) -> glam::DVec3 {
 
 /// Build a UCS whose Z axis is `normal`, anchored at `origin`.
 ///
-/// X and Y come from the Arbitrary Axis Algorithm, the same rule DWG uses to
-/// turn an extrusion direction into an object coordinate system. Picking the
-/// world axis that is *least* parallel to the normal keeps the cross product
-/// well conditioned, and makes the result stable: the same face always yields
-/// the same X axis, so a sketch drawn on it does not spin when the UCS is
-/// rebuilt.
-///
-/// Returns `None` when `normal` is degenerate and defines no plane.
+/// X and Y come from the arbitrary-axis algorithm in
+/// [`crate::scene::view::transform::ocs_axes`], the same frame entities get
+/// from their extrusion direction, so the same face always yields the same X
+/// axis. Returns `None` when `normal` is degenerate and defines no plane.
 pub(super) fn ucs_from_normal(origin: glam::DVec3, normal: glam::DVec3) -> Option<Ucs> {
     let z = normal.normalize_or_zero();
     if z.length_squared() < 1e-12 {
         return None;
     }
-    // 1/64 is the threshold the DWG spec names for "close enough to the world
-    // Z axis that using it as the reference would be ill conditioned".
-    let reference = if z.x.abs() < 1.0 / 64.0 && z.y.abs() < 1.0 / 64.0 {
-        glam::DVec3::Y
-    } else {
-        glam::DVec3::Z
-    };
-    let x = reference.cross(z).normalize_or_zero();
-    if x.length_squared() < 1e-12 {
-        return None;
-    }
-    let y = z.cross(x).normalize_or_zero();
+    let ((xx, xy, xz), (yx, yy, yz)) = crate::scene::view::transform::ocs_axes((z.x, z.y, z.z));
     let mut ucs = Ucs::new("*ACTIVE*");
     ucs.origin = acadrust::types::Vector3::new(origin.x, origin.y, origin.z);
-    ucs.x_axis = acadrust::types::Vector3::new(x.x, x.y, x.z);
-    ucs.y_axis = acadrust::types::Vector3::new(y.x, y.y, y.z);
+    ucs.x_axis = acadrust::types::Vector3::new(xx, xy, xz);
+    ucs.y_axis = acadrust::types::Vector3::new(yx, yy, yz);
     Some(ucs)
 }
 

src/command.rs

@@ -347,23 +347,30 @@ impl CadCommand for ValuePromptCommand {
     }
 }
 
-/// Interactive front-end for `UCS FACE` — Fusion's "create sketch on a face".
+/// Interactive pick for `UCS FACE` and `UCS OBJECT`.
 ///
-/// Picks one face of a solid and hands the resulting plane to the inline
-/// `UCS FACE <handle> <x,y,z>` handler via [`CmdResult::Dispatch`], so the
-/// plane construction lives in exactly one place whether the user clicked a
-/// face or typed the arguments. `entity_pick_uses_surface_point` is what
-/// makes the click land *on the solid's surface* rather than on the current
-/// drawing plane, which is the whole point: the pick coordinate is the face.
-pub struct UcsFaceCommand;
+/// Hands the picked entity to the inline `UCS FACE <handle> <x,y,z>` /
+/// `UCS OBJECT <handle>` handler via [`CmdResult::Dispatch`], so the plane
+/// construction lives in one place whether the user clicked or typed the
+/// arguments. For a face the click lands *on the solid's surface*
+/// (`entity_pick_uses_surface_point`) and that point becomes the plane
+/// origin; for an object only the handle matters.
+pub struct UcsPickCommand {
+    /// `true` picks a solid face; `false` picks a planar entity.
+    pub face: bool,
+}
 
-impl CadCommand for UcsFaceCommand {
+impl CadCommand for UcsPickCommand {
     fn name(&self) -> &'static str {
         "UCS"
     }
 
     fn prompt(&self) -> String {
-        crate::t!("UCS FACE  Select a face to draw on:").into_owned()
+        if self.face {
+            crate::t!("UCS FACE  Select a face to draw on:").into_owned()
+        } else {
+            crate::t!("UCS OBJECT  Select object to align UCS:").into_owned()
+        }
     }
 
     fn needs_entity_pick(&self) -> bool {
@@ -371,7 +378,7 @@ impl CadCommand for UcsFaceCommand {
     }
 
     fn entity_pick_uses_surface_point(&self) -> bool {
-        true
+        self.face
     }
 
     fn entity_pick_highlights_hover(&self) -> bool {
@@ -382,6 +389,9 @@ impl CadCommand for UcsFaceCommand {
         if handle.is_null() {
             return CmdResult::NeedPoint;
         }
+        if !self.face {
+            return CmdResult::Dispatch(format!("UCS OBJECT {:X}", handle.value()));
+        }
         // Hex handle and comma-separated coordinates are what the inline
         // parser reads back. Full `{}` precision, not a rounded format: the
         // point has to stay on the face for the planar-face lookup.

src/locale_catalog.rs

@@ -4149,7 +4149,7 @@ pub(super) fn message_attribute(source: &str) -> Option<(&'static str, &'static
         "TORUS  Specify second end point of tube diameter:" => Some(("model", "torus-specify-second-end-point-of-tube-diameter")),
         "2Point" => Some(("model", "value-2point")),
         "Cube" => Some(("model", "cube")),
-        "UCS  option [World/View/3Point/Z/X/Y/Origin/Save/Delete] or name:" => Some(("view", "ucs-option-world-view-3point-z-x-y-origin-save-delete-or-name")),
+        "UCS  option [Face/OBject/World/View/3Point/Z/X/Y/Origin/Save/Delete] or name:" => Some(("view", "ucs-option-world-view-3point-z-x-y-origin-save-delete-or-name")),
         "UCS  specify new origin:" => Some(("view", "ucs-specify-new-origin")),
         "UCS  specify point on positive X axis:" => Some(("view", "ucs-specify-point-on-positive-x-axis")),
         "UCS  specify point in positive XY plane:" => Some(("view", "ucs-specify-point-in-positive-xy-plane")),

src/modules/view/ucs_cmd.rs

@@ -24,9 +24,13 @@ impl UcsCommand {
         Self::default()
     }
 
-    /// Options that take no further argument and execute immediately.
+    /// Options that take no further typed argument: they execute immediately
+    /// or, for Face / OBject, start their own entity pick.
     fn is_zero_arg(opt: &str) -> bool {
-        matches!(opt, "W" | "WORLD" | "VIEW" | "V" | "LIST" | "?")
+        matches!(
+            opt,
+            "W" | "WORLD" | "VIEW" | "V" | "LIST" | "?" | "FACE" | "F" | "OBJECT" | "OB"
+        )
     }
 
     /// Options whose argument is a coordinate (so a click is accepted too).
@@ -50,7 +54,10 @@ impl CadCommand for UcsCommand {
 
     fn prompt(&self) -> String {
         match self.option.as_deref() {
-            None => t!("UCS  option [World/View/3Point/Z/X/Y/Origin/Save/Delete] or name:").into_owned(),
+            None => t!(
+                "UCS  option [Face/OBject/World/View/3Point/Z/X/Y/Origin/Save/Delete] or name:"
+            )
+            .into_owned(),
             Some("Z") => t!("UCS  rotation angle about Z (degrees):").into_owned(),
             Some("X") => t!("UCS  rotation angle about X (degrees):").into_owned(),
             Some("Y") => t!("UCS  rotation angle about Y (degrees):").into_owned(),