feat(otrack): draw both vectors of an intersection lock

An OTRACK crossing is the meeting of two tracking vectors, but
`OtrackHit` carried only the one a typed distance is measured along, so
the overlay had a single guide to draw. Snapping to the crossing of two
vectors worked and looked like an unexplained point on one line.

Carry the crossed ray out of `otrack_snap` as `OtrackHit::cross`, keep it
on the app beside `otrack_active`, and let the overlay take a list of
guides rather than one. `otrack_active` still drives typed-distance
entry on its own, so distance entry is unchanged.

Fixes HakanSeven12/OpenCADStudio#1313

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQzYZsXBwPZ5HwBaGitEUV
(cherry picked from commit 2f6caacece)

src/app/command_driver.rs

@@ -104,6 +104,7 @@ impl OpenCADStudio {
         self.snapper.from_point = None;
         self.snapper.clear_tracking();
         self.otrack_active = None;
+        self.otrack_cross = None;
         self.otrack_kind = None;
         self.axis_lock_dir = None;
         self.dyn_user_reshaped = false;

src/app/mod.rs

@@ -502,6 +502,11 @@ pub(super) struct OpenCADStudio {
     /// cursor is on a tracking ray. Lets a typed distance place a point along
     /// the ray from the tracking point (issue #69). `None` when not aligned.
     otrack_active: Option<(glam::DVec3, glam::DVec3)>,
+    /// The vector `otrack_active` crosses, when the lock is the meeting of two
+    /// tracking vectors. Drawn beside the first so the user can see that the
+    /// point is their intersection; a typed distance still runs along
+    /// `otrack_active` alone. `None` for a single-ray alignment. (#1313)
+    otrack_cross: Option<(glam::DVec3, glam::DVec3)>,
     /// Active OTRACK ray kind, separate from typed-distance geometry.
     otrack_kind: Option<crate::snap::TrackingKind>,
     /// Whether Tangent snap was enabled before a tangent-pick command started.
@@ -3868,6 +3873,7 @@ impl OpenCADStudio {
             annotation_auto_scale: -4,
             last_saved_config: None,
             otrack_active: None,
+            otrack_cross: None,
             otrack_kind: None,
             clean_screen: false,
             quick_properties: false,

src/app/update/mod.rs

@@ -366,6 +366,7 @@ impl OpenCADStudio {
         {
             self.snapper.clear_tracking();
             self.otrack_active = None;
+            self.otrack_cross = None;
             self.otrack_kind = None;
         }
         if let Some((started, tab_id, before)) = perf_edit_before {
@@ -402,6 +403,7 @@ impl OpenCADStudio {
     pub(in crate::app) fn reset_tracking_after_point(&mut self) {
         self.snapper.clear_tracking();
         self.otrack_active = None;
+        self.otrack_cross = None;
         self.otrack_kind = None;
     }
 
@@ -3982,6 +3984,7 @@ impl OpenCADStudio {
                 if !self.snapper.otrack_enabled {
                     self.snapper.clear_tracking();
                     self.otrack_active = None;
+                    self.otrack_cross = None;
                     self.otrack_kind = None;
                 }
                 Task::none()

src/app/update/viewport.rs

@@ -1479,6 +1479,7 @@ impl OpenCADStudio {
                 Some((base, dir))
             });
             self.otrack_active = otrack_hit.map(|hit| (hit.base, hit.dir)).or(drafting_guide);
+            self.otrack_cross = otrack_hit.and_then(|hit| hit.cross);
 
             self.otrack_kind = otrack_hit.map(|hit| hit.kind);
 
@@ -2190,6 +2191,7 @@ impl OpenCADStudio {
                 None
             };
             self.otrack_active = otrack_hit.map(|h| (h.base, h.dir));
+            self.otrack_cross = otrack_hit.and_then(|h| h.cross);
             self.otrack_kind = otrack_hit.map(|h| h.kind);
 
             // Parallel snap: with nothing else snapped or tracked, lock
@@ -2208,6 +2210,7 @@ impl OpenCADStudio {
                         (self.last_point, self.snapper.parallel_ref)
                     {
                         self.otrack_active = Some((base, dir.as_dvec3()));
+                        self.otrack_cross = None;
                     }
                     self.tabs[i].snap_result = Some(par);
                 }

src/app/view/mod.rs

@@ -770,15 +770,22 @@ bg={bg_ms:.1}ms n={view_count}"
             // The active alignment vector: a dashed guide from the acquired
             // tracking point through the locked cursor, so the user sees the
             // extension / tracking line they are snapped to (#219).
-            let otrack_line: Option<(iced::Point, iced::Point)> =
-                match (otrack_proj, self.otrack_active) {
-                    (Some((view_rot, eye, ob)), Some((base, _dir))) => {
-                        let b = ost_project(base, view_rot, eye, ob);
-                        let a = ost_project(tab.last_cursor_world, view_rot, eye, ob);
-                        (b.x.is_finite() && a.x.is_finite()).then_some((b, a))
-                    }
-                    _ => None,
-                };
+            // An intersection lock is the meeting of two tracking vectors, so
+            // both are drawn — one guide alone hides what the point is (#1313).
+            let otrack_lines: Vec<(iced::Point, iced::Point)> = match otrack_proj {
+                Some((view_rot, eye, ob)) => {
+                    let a = ost_project(tab.last_cursor_world, view_rot, eye, ob);
+                    self.otrack_active
+                        .into_iter()
+                        .chain(self.otrack_cross)
+                        .filter_map(|(base, _dir)| {
+                            let b = ost_project(base, view_rot, eye, ob);
+                            (b.x.is_finite() && a.x.is_finite()).then_some((b, a))
+                        })
+                        .collect()
+                }
+                None => vec![],
+            };
             // The acquired Parallel-snap reference, marked on its line (#277).
             let parallel_ref_marker: Option<iced::Point> =
                 match (otrack_proj, self.snapper.parallel_ref) {
@@ -894,7 +901,7 @@ bg={bg_ms:.1}ms n={view_count}"
                 grip_clip,
                 ucs_icons,
                 ost_points,
-                otrack_line,
+                otrack_lines,
                 parallel_ref_marker,
                 // ViewCube hover region matches the drawn cube — gone when hidden.
                 !is_paper && viewcube_visible,