README.md

@@ -33,9 +33,18 @@ cargo run --features app --bin openvistapro_app
 The crate’s default `cargo run` target is the CLI binary (`openvistapro`), so the commands above work without an extra `--bin` flag. Use `--features app --bin openvistapro_app` for the optional GUI shell.
 
 The optional app shell is gated behind the `app` feature so default CLI builds stay GPU-free.
-It opens an `eframe`/`egui` window titled `OpenVistaPro` with scene controls, top-level menus/dialogs, and a CPU-rendered terrain preview.
+It opens an `eframe`/`egui` window titled `OpenVistaPro` with scene controls, top-level menus/dialogs, a Terrain section, and a CPU-rendered terrain preview.
 The native shell uses eframe's Glow renderer under X11/Xvfb, which keeps the app smoke launch independent of WGPU backend feature selection.
 
+Terrain workflow in the GUI:
+
+- Open the Terrain section in the left dock, or use Terrain → Generate current preset from the top menu.
+- Choose Plane, Radial hill, or Fractal noise; when Fractal noise is selected, edit the Fractal seed field.
+- Click Generate current preset to build the active preset into the live preview.
+- Generated terrain updates the preview directly; if generation fails, the previous imported terrain stays in place.
+
+This GUI path is interactive preview-first. The CLI `cargo run -- render --preset fractal --seed 1337 ...` path writes an output image, and script workflows use `use preset fractal` plus `render output ...` to drive the same generation boundary non-interactively.
+
 Importer status:
 
 - `heightmap`: project-owned script input that imports grayscale PNG heightmaps with `import heightmap "path.png"` and maps brightness to elevation. This is a terrain-ingest convenience path, not a legacy VistaPro compatibility claim.

docs/knowledgebase/ui-panel-map.md

@@ -7,7 +7,7 @@ This is a normalized modern shell map derived from the VistaPro manuals, screens
 | Modern panel | VistaPro surfaces it absorbs | Suggested placement | Current code support | Notes / gaps |
 |---|---|---|---|---|
 | Viewport / preview | Main render window, map preview, perspective view, preview/final render output | Center dock | Partial | `src/app.rs` renders the CPU preview into `CentralPanel`; perspective and top-down preview modes exist, but there is no GPU viewport or direct manipulation overlay yet. |
-| Terrain / import | Load Landscape, Import, terrain source selection, generated terrain presets | Left dock or collapsible section | Partial | The current shell exposes project-owned terrain presets (`Plane`, `RadialHill`) and a working heightmap import action; legacy format import UI is still absent. |
+| Terrain / import | Load Landscape, Import, terrain source selection, generated terrain presets | Left dock or collapsible section | Partial | The current shell exposes project-owned terrain presets (`Plane`, `Radial hill`, `Fractal noise`) plus a `Fractal seed` field and `Generate current preset` action, alongside a working heightmap import action; the GUI builds terrain into the live preview, while CLI/script workflows drive the same generator non-interactively. Legacy format import UI is still absent. |
 | Scene / camera | Camera and target gadgets, lens/range, bank/heading/pitch, water/tree/snow/haze controls | Left dock or inspector stack | Partial | Position/target, explicit heading/pitch/bank controls, lens/FOV/clip range controls, vertical exaggeration, lighting direction/intensity gadgets, color-map editing, and hydrology overlays now live in `src/app.rs` and `src/app_state.rs`; `src/scene.rs`, `src/render.rs`, and `src/script_exec.rs` carry the model/render semantics. The shell covers the main VistaPro scene controls, but its camera semantics are intentionally simplified and not yet tied to any map-click placement workflow. |
 | Render | Preview vs final render, quality/smoothing, detail tradeoffs | Left dock, toolbar, or render tab | Partial | Current code now exposes preview/balanced/final quality presets alongside top-down vs perspective render mode; the shell still lacks the full legacy menu chrome and fine-grained smoothing sliders. |
 | Scripts / paths | Script menu, Run Script, MakePath path tools, animation-frame workflows | Right dock or modal workflow | Partial | Script parsing/execution and MakePath-style path generation now run end-to-end in the backend; the shell surfaces a script editor, Run Script, and Make Path controls, but animation-frame export and richer path editing are still future work. |

src/app.rs

@@ -138,6 +138,13 @@ impl OpenVistaProApp {
                     }
                 });
 
+                ui.menu_button("Terrain", |ui| {
+                    if ui.button("Generate current preset").clicked() {
+                        changed |= self.generate_current_terrain(action_note);
+                        ui.close();
+                    }
+                });
+
                 ui.menu_button("Tools", |ui| {
                     if ui.button("Run script").clicked() {
                         let base_dir = std::path::Path::new(Self::default_script_base_dir());
@@ -200,7 +207,7 @@ impl OpenVistaProApp {
                 ui.label(self.shell.section_summary());
                 ui.separator();
                 match self.shell.active_section {
-                    ShellSection::Terrain => changed |= self.terrain_controls(ui),
+                    ShellSection::Terrain => changed |= self.terrain_controls(ui, action_note),
                     ShellSection::Scene => changed |= self.scene_controls(ui),
                     ShellSection::Render => changed |= self.render_controls(ui),
                     ShellSection::Import => changed |= self.import_controls(ui, action_note),
@@ -212,7 +219,7 @@ impl OpenVistaProApp {
         changed
     }
 
-    fn terrain_controls(&mut self, ui: &mut egui::Ui) -> bool {
+    fn terrain_controls(&mut self, ui: &mut egui::Ui, action_note: &mut Option<String>) -> bool {
         let mut changed = false;
         let mut preset = self.data.terrain_preset;
         changed |= ui
@@ -234,6 +241,29 @@ impl OpenVistaProApp {
             self.data.apply(AppAction::SetTerrainPreset(preset));
         }
 
+        ui.separator();
+        ui.horizontal(|ui| {
+            if ui.button("Generate current preset").clicked() {
+                changed |= self.generate_current_terrain(action_note);
+            }
+            ui.label("Build the active terrain preset into the preview.");
+        });
+        if let Some(grid) = self.data.generated_grid.as_ref() {
+            ui.label(format!(
+                "Generated terrain: {}×{}",
+                grid.width(),
+                grid.height()
+            ));
+        } else if let Some(grid) = self.data.imported_grid.as_ref() {
+            ui.label(format!(
+                "Imported terrain: {}×{}",
+                grid.width(),
+                grid.height()
+            ));
+        } else {
+            ui.label("The preview is still showing the current preset directly.");
+        }
+
         ui.separator();
         ui.label("Fractal seed");
         let mut seed = self.data.terrain_seed;
@@ -248,6 +278,25 @@ impl OpenVistaProApp {
         changed
     }
 
+    fn generate_current_terrain(&mut self, action_note: &mut Option<String>) -> bool {
+        let terrain_label = self.data.terrain_preset.label();
+        match self.data.generate_terrain() {
+            Ok(grid) => {
+                *action_note = Some(format!(
+                    "generated {} terrain into {}×{} preview",
+                    terrain_label,
+                    grid.width(),
+                    grid.height()
+                ));
+                true
+            }
+            Err(error) => {
+                *action_note = Some(format!("terrain generation failed: {error}"));
+                false
+            }
+        }
+    }
+
     fn render_controls(&mut self, ui: &mut egui::Ui) -> bool {
         let mut changed = false;
         let mut renderer_mode = self.data.renderer_mode;

src/app_state.rs

@@ -168,6 +168,9 @@ pub struct AppData {
     pub import_path: Option<String>,
     /// Path-tool target or summary.
     pub path_target: Option<String>,
+    /// Generated terrain currently active in the preview, if the shell has
+    /// explicitly generated the current preset.
+    pub generated_grid: Option<HeightGrid>,
     /// Current script source text edited in the Scripts / paths panel.
     pub script_source: String,
     /// Height grid currently imported through the shell.
@@ -194,6 +197,7 @@ impl Default for AppData {
             loaded_scene_path: Some(scene_path),
             import_path: Some(import_path.clone()),
             path_target: None,
+            generated_grid: None,
             script_source: format!(
                 "use preset hill\nimport heightmap \"{import_path}\"\nset thresholds water=1.0 tree=4.0 snow=7.0\nrender output \"{script_output}\"\n"
             ),
@@ -207,8 +211,18 @@ impl Default for AppData {
 impl AppData {
     pub fn apply(&mut self, action: AppAction) {
         match action {
-            AppAction::SetTerrainPreset(preset) => self.terrain_preset = preset,
-            AppAction::SetTerrainSeed(seed) => self.terrain_seed = seed,
+            AppAction::SetTerrainPreset(preset) => {
+                self.terrain_preset = preset;
+                if self.generated_grid.is_some() {
+                    let _ = self.refresh_generated_grid();
+                }
+            }
+            AppAction::SetTerrainSeed(seed) => {
+                self.terrain_seed = seed;
+                if self.generated_grid.is_some() {
+                    let _ = self.refresh_generated_grid();
+                }
+            }
             AppAction::SetRendererMode(mode) => self.renderer_mode = mode,
             AppAction::SetRenderQuality(quality) => self.render_quality = quality,
             AppAction::SetWaterLevel(value) => self.scene.water_level = value,
@@ -275,6 +289,9 @@ impl AppData {
             AppAction::SetPalette(palette) => self.scene.palette = palette,
             AppAction::SetPreviewSize { width, height } => {
                 self.preview_size = (width.max(1), height.max(1));
+                if self.generated_grid.is_some() {
+                    let _ = self.refresh_generated_grid();
+                }
             }
             AppAction::SetLoadedScenePath(path) => self.loaded_scene_path = path,
             AppAction::SetScriptSource(source) => self.script_source = source,
@@ -283,6 +300,7 @@ impl AppData {
 
     pub fn reset_scene(&mut self) {
         self.scene = Scene::default();
+        self.generated_grid = None;
         self.imported_grid = None;
         self.generated_path = None;
         self.last_script_run = None;
@@ -295,6 +313,7 @@ impl AppData {
     pub fn open_scene(&mut self, path: &Path) -> Result<(), SceneFileError> {
         let scene = scene_file::load_from_path(path)?;
         self.scene = scene;
+        self.generated_grid = None;
         self.imported_grid = None;
         self.generated_path = None;
         self.last_script_run = None;
@@ -314,6 +333,7 @@ impl AppData {
     ) -> Result<(), Box<dyn std::error::Error>> {
         let source = std::fs::read_to_string(path)?;
         let imported = crate::import::import_ovp_text(&source)?;
+        self.generated_grid = None;
         self.imported_grid = Some(imported.into_grid());
         self.import_path = Some(path.display().to_string());
         Ok(())
@@ -325,6 +345,15 @@ impl AppData {
         Ok(report)
     }
 
+    /// Generates the current terrain preset and makes it the active preview source.
+    pub fn generate_terrain(&mut self) -> Result<&HeightGrid, TerrainError> {
+        self.refresh_generated_grid()?;
+        Ok(self
+            .generated_grid
+            .as_ref()
+            .expect("generated grid just refreshed"))
+    }
+
     pub fn make_path(&mut self) -> CameraPath {
         let path = build_demo_path(&self.scene);
         self.path_target = Some(format!(
@@ -338,6 +367,9 @@ impl AppData {
     }
 
     fn active_height_grid(&self) -> Result<HeightGrid, TerrainError> {
+        if let Some(grid) = &self.generated_grid {
+            return Ok(grid.clone());
+        }
         if let Some(grid) = &self.imported_grid {
             return Ok(grid.clone());
         }
@@ -370,7 +402,8 @@ impl AppData {
             import_path: self.import_path.clone(),
             path_target: self.path_target.clone(),
             status_line: format!(
-                "CPU preview · {} · {} · {} · exag {:.2} · {width}×{height}",
+                "CPU preview · {} · {} · {} · {} · exag {:.2} · {width}×{height}",
+                self.terrain_source_label(),
                 terrain_status,
                 self.renderer_mode.label(),
                 self.render_quality.label(),
@@ -384,6 +417,24 @@ impl AppData {
         self.active_height_grid()
     }
 
+    fn refresh_generated_grid(&mut self) -> Result<(), TerrainError> {
+        let (width, height) = self.preview_size;
+        let grid = self.terrain_preset.build_grid(width, height)?;
+        self.imported_grid = None;
+        self.generated_grid = Some(grid);
+        Ok(())
+    }
+
+    fn terrain_source_label(&self) -> &'static str {
+        if self.generated_grid.is_some() {
+            "generated terrain"
+        } else if self.imported_grid.is_some() {
+            "imported terrain"
+        } else {
+            "preset terrain"
+        }
+    }
+
     pub fn render_preview(&self) -> Result<RgbImage, TerrainError> {
         let grid = self.build_preview_grid()?;
         let (width, height) = self.preview_size;
@@ -461,6 +512,7 @@ mod tests {
         assert_eq!(app.preview_size, (256, 256));
         assert!(app.loaded_scene_path.is_some());
         assert!(app.script_source.contains("import heightmap"));
+        assert!(app.generated_grid.is_none());
     }
 
     #[test]
@@ -584,6 +636,49 @@ mod tests {
         assert_ne!(preview.as_raw(), final_img.as_raw());
     }
 
+    #[test]
+    fn perspective_renderer_changes_the_gui_preview_path() {
+        let mut app = AppData::default();
+        app.apply(AppAction::SetPreviewSize {
+            width: 48,
+            height: 32,
+        });
+
+        let top_down = app.render_preview().unwrap();
+        app.apply(AppAction::SetRendererMode(RendererMode::Perspective));
+        let perspective = app.render_preview().unwrap();
+        let snapshot = app.ui_snapshot();
+
+        assert_eq!(perspective.width(), 48);
+        assert_eq!(perspective.height(), 32);
+        assert_ne!(top_down.as_raw(), perspective.as_raw());
+        assert!(snapshot.status_line.contains("Perspective"));
+    }
+
+    #[test]
+    fn fractal_seed_changes_the_gui_preview_terrain() {
+        let mut app = AppData::default();
+        app.apply(AppAction::SetPreviewSize {
+            width: 48,
+            height: 32,
+        });
+        app.apply(AppAction::SetRendererMode(RendererMode::Perspective));
+        app.apply(AppAction::SetTerrainPreset(TerrainPreset::Fractal {
+            seed: 2,
+        }));
+
+        let seed_two = app.render_preview().unwrap();
+        app.apply(AppAction::SetTerrainSeed(9001));
+        app.apply(AppAction::SetTerrainPreset(TerrainPreset::Fractal {
+            seed: 9001,
+        }));
+        let seed_nine_thousand_one = app.render_preview().unwrap();
+
+        assert_eq!(seed_two.width(), 48);
+        assert_eq!(seed_two.height(), 32);
+        assert_ne!(seed_two.as_raw(), seed_nine_thousand_one.as_raw());
+    }
+
     #[test]
     fn ui_snapshot_exposes_existing_controls_and_new_entry_points() {
         let app = AppData::default();
@@ -601,6 +696,7 @@ mod tests {
         assert!(shell.import_path.is_some());
         assert!(shell.path_target.is_none());
         assert!(shell.status_line.contains("CPU preview"));
+        assert!(shell.status_line.contains("preset terrain"));
         assert!(shell.status_line.contains("Preview"));
     }
 
@@ -634,6 +730,44 @@ mod tests {
         assert!(app.imported_grid.is_some());
     }
 
+    #[test]
+    fn generate_terrain_replaces_imported_preview_source() {
+        let mut app = AppData::default();
+        let fixture = Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("tests/fixtures/open/tiny-heightfield.ovptext");
+
+        app.import_heightmap_from_path(&fixture)
+            .expect("import fixture");
+        let preview_size = app.preview_size;
+        let generated_dims = {
+            let generated = app.generate_terrain().expect("generate terrain");
+            (generated.width(), generated.height())
+        };
+        let grid = app.build_preview_grid().expect("preview grid");
+
+        assert_eq!(generated_dims.0, preview_size.0);
+        assert_eq!(generated_dims.1, preview_size.1);
+        assert_eq!(grid.width(), preview_size.0);
+        assert!(app.imported_grid.is_none());
+        assert!(app.generated_grid.is_some());
+        assert!(app.ui_snapshot().status_line.contains("generated terrain"));
+    }
+
+    #[test]
+    fn generated_terrain_tracks_preset_changes() {
+        let mut app = AppData::default();
+        app.generate_terrain().expect("generate terrain");
+        let before = app
+            .build_preview_grid()
+            .expect("preview grid before change");
+
+        app.apply(AppAction::SetTerrainPreset(TerrainPreset::Plane));
+        let after = app.build_preview_grid().expect("preview grid after change");
+
+        assert!(before.min_max().expect("generated grid has min/max").1 > 0.0);
+        assert_eq!(after.min_max(), Some((0.0, 0.0)));
+    }
+
     #[test]
     fn make_path_produces_a_three_keyframe_summary() {
         let mut app = AppData::default();