Grid: stay on the ground (XY) by default; following the view is a preference (#2035)

#1583 turned the grid to the upright origin plane in side views for
everyone. That is now Preferences > Grid follows the view, off by
default; headless pictures keep the ground grid.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

assets/locales/en.json

@@ -1146,6 +1146,8 @@
   "ui.fully_constrained": "Fully constrained",
   "ui.general": "General",
   "ui.graphics": "Graphics",
+  "ui.grid_follows_view": "Grid follows the view",
+  "ui.grid_follows_view_hint": "Side views show the grid on the upright plane facing them instead of the ground",
   "ui.ground_shadow": "Ground shadow",
   "ui.groupSelected": "Group Selected",
   "ui.heading_add_ins": "ADD-INS",

crates/engine/src/view.rs

@@ -390,13 +390,13 @@ fn build_scene(
     };
     let b = bounds(s);
     sc.radius = (b.diagonal() * 0.5).max(cam.half_height()).max(10.0) + b.center().dist(cam.target);
-    // Grid on the ground plane (XY with Z up, XZ with Y up), or the upright origin plane facing
+    // Grid on the ground plane (XY with Z up, XZ with Y up), drawn under the model as in the viewport.
-    // a view that sees the ground edge-on ([`grid_plane`]), drawn under the model as in the viewport.
     if guides.grid {
         let (minor, major) = grid_step(cam.half_height());
         let ext = (cam.half_height() * 3.0 / major).ceil() * major;
         let tf = cam.to_frame(cam.target);
-        let (u, v) = grid_plane(cam.to_frame(cam.back()));
+        // Headless pictures keep the grid on the ground, the viewport's default.
+        let (u, v) = (Vec3::X, Vec3::Y);
         let snap = |a: Vec3| a * ((tf.dot(a) / major).round() * major);
         let c = snap(u) + snap(v);
         let w = |p: Vec3| cam.from_frame(p);

crates/ui-egui/src/prefs.rs

@@ -280,6 +280,9 @@ pub struct Prefs {
     pub space_mouse_axis_speed: [f32; 6],
     /// Anti-aliasing samples (applies on restart).
     pub msaa: u32,
+    /// The grid turns to the upright origin plane facing a side view (#1470). Off by default: the
+    /// grid stays on the ground plane (XY) whatever the view.
+    pub grid_follows_view: bool,
     /// How finely the viewport tessellates curved faces and edges: `coarse`, `normal`, `fine` or
     /// `ultra` (#1287). Only the display plan the viewport draws; never the design or exports.
     pub display_quality: String,
@@ -410,6 +413,7 @@ impl Default for Prefs {
             space_mouse_reverse: [false; 6],
             space_mouse_axis_speed: [1.0; 6],
             msaa: 4,
+            grid_follows_view: false,
             display_quality: "normal".into(),
             supersampling: 1.0,
             supersampling_adaptive: true,
@@ -1265,6 +1269,10 @@ fn page(app: &mut SolveApp, ui: &mut egui::Ui, t: &Tokens) {
             ui.label(crate::i18n::tr_label("Grid"));
             ui.checkbox(&mut app.ui.show_grid, "");
             ui.end_row();
+            ui.label(crate::i18n::tr_label("Grid follows the view"));
+            ui.add_enabled(app.ui.show_grid, egui::Checkbox::without_text(&mut app.preferences.grid_follows_view))
+                .on_hover_text(crate::i18n::tr_label("Side views show the grid on the upright plane facing them instead of the ground"));
+            ui.end_row();
             ui.label(crate::i18n::tr_label("Ground shadow"));
             ui.checkbox(&mut app.ui.ground_shadow, "");
             ui.end_row();

crates/ui-egui/src/update/install.rs

@@ -290,7 +290,10 @@ fn unzip_one(zip: &Path, name: &str, to: &Path) -> Result<bool, String> {
     let file = std::fs::File::open(zip).map_err(|e| format!("{}: {e}", zip.display()))?;
     let mut archive = zip::ZipArchive::new(file).map_err(|e| format!("{}: {e}", zip.display()))?;
     let index = (0..archive.len()).find(|&i| {
-        archive.name_for_index(i).is_some_and(|n| n.rsplit(['/', '\\']).next().is_some_and(|f| f.eq_ignore_ascii_case(name)) && !n.ends_with('/'))
+        archive
+            .name_for_index(i)
+            .and_then(Result::ok)
+            .is_some_and(|n| n.rsplit(['/', '\\']).next().is_some_and(|f| f.eq_ignore_ascii_case(name)) && !n.ends_with('/'))
     });
     let Some(index) = index else { return Ok(false) };
     let mut entry = archive.by_index(index).map_err(|e| format!("{}: {e}", zip.display()))?;

crates/ui-egui/src/viewport.rs

@@ -733,7 +733,8 @@ fn build_sketch_scene(app: &SolveApp, proj: &Proj) -> GpuScene {
         // The ground plane: XY with Z up, XZ with Y up (laid out in the camera's Z-up frame), or
         // the upright origin plane facing the view when the ground is seen edge-on.
         let tf = app.cam.to_frame(app.cam.target);
-        let (u, v) = grid_plane(app.cam.to_frame(app.cam.back()));
+        // On the ground (XY) unless the Grid follows the view preference is on (#1470).
+        let (u, v) = if app.preferences.grid_follows_view { grid_plane(app.cam.to_frame(app.cam.back())) } else { (Vec3::X, Vec3::Y) };
         let snap = |a: Vec3| a * ((tf.dot(a) / major).round() * major);
         let c = snap(u) + snap(v);
         let w3 = |p: Vec3| app.cam.from_frame(p).to_f32();