fix(render): select terrain LOD from native camera cells

README.md

@@ -9,6 +9,8 @@
 прототипа, а поддерживаемые Control-анимации и эффекты обновляются по общим
 часам сцены. Неподдерживаемые Control-треки остаются на сохранённой начальной
 позе.
+Рельеф переключает исходные LOD0/LOD1 по ячейкам относительно текущей камеры;
+под основаниями строений сохраняется подробная сетка.
 
 ## Запуск
 

adapters/fparkan-render-vulkan/src/asset_mesh.rs

@@ -1105,7 +1105,21 @@ fn project_land_msh_to_static_mesh_with_lod0(
 pub fn project_land_msh_to_static_mesh_in_world_space(
     terrain: &LandMeshDocument,
 ) -> Result<VulkanStaticMesh, VulkanAssetMeshError> {
-    let lod0 = static_terrain_lod0_assignments(terrain)?;
+    project_land_msh_lod_to_static_mesh_in_world_space(terrain, TerrainLod::Lod0)
+}
+
+/// Projects one authored terrain LOD without changing source positions or attributes.
+///
+/// # Errors
+/// Returns an error for invalid slot assignments or an empty selected LOD.
+pub fn project_land_msh_lod_to_static_mesh_in_world_space(
+    terrain: &LandMeshDocument,
+    lod: TerrainLod,
+) -> Result<VulkanStaticMesh, VulkanAssetMeshError> {
+    let mut lod0 = terrain
+        .face_lod_assignments()
+        .map_err(VulkanAssetMeshError::InvalidTerrainLodMapping)?;
+    lod0.retain(|assignment| assignment.lod == lod);
     let indices = static_terrain_indices(terrain, &lod0)?;
     let vertices = terrain
         .positions
@@ -2118,6 +2132,13 @@ mod tests {
         assert_eq!(mesh.draw_ranges[0].index_count, 6);
         assert_eq!(mesh.draw_ranges[0].material_index, 0x0101);
 
+        let far = project_land_msh_lod_to_static_mesh_in_world_space(&terrain, TerrainLod::Lod1)
+            .expect("LOD1 terrain projection");
+        assert_eq!(far.indices, [3, 4, 5, 3, 4, 5]);
+        assert_eq!(far.draw_ranges.len(), 1);
+        assert_eq!(far.draw_ranges[0].material_index, 0x0202);
+        assert_eq!(far.vertices[3].position, [10.0, 10.0, 10.0]);
+
         terrain.nodes_raw.clear();
         assert!(matches!(
             project_land_msh_to_static_mesh_in_world_space(&terrain),

adapters/fparkan-render-vulkan/src/ffi.rs

@@ -22,7 +22,8 @@ mod validation;
 
 pub use self::asset_mesh::{
     node38_pose, node38_pose_from_hierarchy, node38_pose_relative_to_root,
-    node38_pose_relative_to_root_from_hierarchy, project_land_msh_to_static_mesh,
+    node38_pose_relative_to_root_from_hierarchy,
+    project_land_msh_lod_to_static_mesh_in_world_space, project_land_msh_to_static_mesh,
     project_land_msh_to_static_mesh_in_world_space, project_land_msh_to_static_mesh_in_xy_frame,
     project_msh_to_static_mesh, project_msh_to_static_mesh_in_world_space,
     project_msh_to_static_mesh_in_world_space_with_node_fallback_poses,

apps/fparkan-game/src/main.rs

@@ -3,6 +3,7 @@
 //! `FParkan` render-planning composition root.
 
 mod camera_capture;
+mod terrain_lod;
 
 #[cfg(test)]
 use camera_capture::parse_legacy_camera_capture;
@@ -4626,6 +4627,7 @@ fn multiply_row_major(left: [f32; 16], right: [f32; 16]) -> [f32; 16] {
 
 struct StaticPreviewScene {
     mesh: VulkanStaticMesh,
+    terrain_lod: Option<terrain_lod::TerrainLodDraws>,
     native_handedness_by_range: HashMap<usize, i8>,
     type16_present_ranges: HashSet<usize>,
     materials: Vec<VulkanStaticMaterial>,
@@ -8019,6 +8021,11 @@ fn static_preview_mesh_and_materials(
         terrain,
         foundation,
     )?;
+    let (terrain_component, terrain_lod) = terrain_lod::prepare(
+        terrain_mesh,
+        terrain_component,
+        terrain_query.basement_foundation(),
+    )?;
     let terrain_materials = static_preview_terrain_base_materials(
         &mut terrain_material_loader,
         root,
@@ -8521,6 +8528,7 @@ fn static_preview_mesh_and_materials(
     let shadow_material_index = append_shadow_material(&mut materials)?;
     Ok(StaticPreviewScene {
         mesh,
+        terrain_lod,
         native_handedness_by_range,
         type16_present_ranges,
         materials,
@@ -9333,6 +9341,7 @@ fn run_static_vulkan_mode(
 
 struct StaticVulkanApp {
     mesh: VulkanStaticMesh,
+    terrain_lod: Option<terrain_lod::TerrainLodDraws>,
     native_handedness_by_range: HashMap<usize, i8>,
     type16_present_ranges: HashSet<usize>,
     materials: Vec<VulkanStaticMaterial>,
@@ -9439,6 +9448,7 @@ impl StaticVulkanApp {
             .collect();
         Self {
             mesh: preview.mesh,
+            terrain_lod: preview.terrain_lod,
             native_handedness_by_range: preview.native_handedness_by_range,
             type16_present_ranges: preview.type16_present_ranges,
             materials: preview.materials,
@@ -9509,6 +9519,12 @@ impl StaticVulkanApp {
         renderer: &mut VulkanSmokeRenderer,
         aspect: f32,
     ) -> Result<(), String> {
+        if let Some(lod) = &self.terrain_lod {
+            lod.report(
+                self.view_camera.position,
+                horizontal_fov(&self.view_camera, aspect),
+            )?;
+        }
         let approximate_portals = self
             .world_range_indices
             .iter()
@@ -9573,18 +9589,26 @@ impl StaticVulkanApp {
                 .map_err(|error| {
                     format!("configure world material category {range_index}: {error}")
                 })?;
-            renderer
-                .set_draw_range_index_count(
+            let count = world_draw_range_index_count(
+                &self.mesh,
+                range,
+                range.index_count,
+                effective_alpha,
+                self.view_camera.position,
+                self.native_handedness_by_range.get(&range_index).copied(),
+            );
+            let count = if let Some(lod) = &self.terrain_lod {
+                lod.index_count(
                     range_index,
-                    world_draw_range_index_count(
-                        &self.mesh,
-                        range,
-                        range.index_count,
-                        effective_alpha,
-                        self.view_camera.position,
-                        self.native_handedness_by_range.get(&range_index).copied(),
-                    ),
-                )
+                    count,
+                    self.view_camera.position,
+                    horizontal_fov(&self.view_camera, aspect),
+                )?
+            } else {
+                count
+            };
+            renderer
+                .set_draw_range_index_count(range_index, count)
                 .map_err(|error| {
                     format!("configure world draw range {range_index} count: {error}")
                 })?;
@@ -9642,6 +9666,7 @@ impl StaticVulkanApp {
         type16_present_ranges: &HashSet<usize>,
         world_range_index_counts: &HashMap<usize, u32>,
         native_handedness_by_range: &HashMap<usize, i8>,
+        terrain_lod: Option<&terrain_lod::TerrainLodDraws>,
         eye_world: [f32; 3],
         horizontal_fov: f32,
         active_materials: &HashMap<usize, ActiveMaterialState>,
@@ -9686,6 +9711,11 @@ impl StaticVulkanApp {
                 eye_world,
                 native_handedness_by_range.get(&range_index).copied(),
             );
+            let count = if let Some(lod) = terrain_lod {
+                lod.index_count(range_index, count, eye_world, horizontal_fov)?
+            } else {
+                count
+            };
             renderer
                 .set_draw_range_index_count(range_index, count)
                 .map_err(|error| format!("update world draw range {range_index} count: {error}"))?;
@@ -10295,6 +10325,7 @@ impl StaticVulkanApp {
             &self.type16_present_ranges,
             &self.world_range_index_counts,
             &self.native_handedness_by_range,
+            self.terrain_lod.as_ref(),
             frame.camera.position,
             horizontal_fov(&frame.camera, frame.aspect),
             &frame.material_update.active_materials,
@@ -13571,6 +13602,7 @@ mod tests {
         };
         let view_camera = free_camera.preview_frame(16.0 / 9.0);
         let preview = StaticPreviewScene {
+            terrain_lod: None,
             mesh: VulkanStaticMesh {
                 vertices: [[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]
                     .into_iter()

apps/fparkan-game/src/terrain_lod.rs

@@ -0,0 +1,286 @@
+use fparkan_render_vulkan::{
+    project_land_msh_lod_to_static_mesh_in_world_space, VulkanStaticDrawRange, VulkanStaticMesh,
+};
+use fparkan_terrain::{BasementFoundation, TerrainLod, TerrainLodPlan};
+use fparkan_terrain_format::LandMeshDocument;
+
+pub(super) struct TerrainLodDraws {
+    plan: TerrainLodPlan,
+    ranges: Vec<(Option<usize>, TerrainLod)>,
+}
+
+impl TerrainLodDraws {
+    pub(super) fn index_count(
+        &self,
+        range: usize,
+        count: u32,
+        eye: [f32; 3],
+        fov: f32,
+    ) -> Result<u32, String> {
+        let Some(&(Some(node), lod)) = self.ranges.get(range) else {
+            return Ok(count);
+        };
+        let selected = self
+            .plan
+            .selected_lod(node, [eye[0], eye[1]], fov)
+            .ok_or_else(|| "invalid terrain LOD camera or cell".to_string())?;
+        Ok(if selected == lod { count } else { 0 })
+    }
+
+    pub(super) fn report(&self, eye: [f32; 3], fov: f32) -> Result<(), String> {
+        let mut counts = [0; 2];
+        for (range, &(_, lod)) in self.ranges.iter().enumerate() {
+            if self.index_count(range, 1, eye, fov)? != 0 {
+                counts[usize::from(lod == TerrainLod::Lod1)] += 1;
+            }
+        }
+        eprintln!(
+            "render_coverage terrain_lod_selected_ranges lod0={} lod1={}",
+            counts[0], counts[1]
+        );
+        Ok(())
+    }
+}
+
+pub(super) fn prepare(
+    terrain: &LandMeshDocument,
+    mut near_mesh: VulkanStaticMesh,
+    foundation: Option<&BasementFoundation>,
+) -> Result<(VulkanStaticMesh, Option<TerrainLodDraws>), String> {
+    let assignments = terrain.face_lod_assignments().map_err(|e| e.to_string())?;
+    if !assignments.iter().any(|a| a.lod == TerrainLod::Lod1) {
+        return Ok((near_mesh, None));
+    }
+    let plan = TerrainLodPlan::new(terrain, foundation)
+        .map_err(|e| format!("prepare terrain LOD: {e}"))?;
+    let near_nodes = if let Some(foundation) = foundation {
+        foundation
+            .fragments
+            .iter()
+            .map(|fragment| {
+                fragment
+                    .source_face
+                    .map(|face| {
+                        plan.source_face_node(face)
+                            .ok_or_else(|| "foundation LOD source face is missing".to_string())
+                    })
+                    .transpose()
+            })
+            .collect::<Result<Vec<_>, _>>()?
+    } else {
+        assignments
+            .iter()
+            .filter(|a| a.lod == TerrainLod::Lod0)
+            .map(|a| Some(a.node_index))
+            .collect()
+    };
+    let mut ranges = split_ranges(&mut near_mesh, &near_nodes, TerrainLod::Lod0)?;
+    if plan.has_far_geometry() {
+        let mut far_mesh =
+            project_land_msh_lod_to_static_mesh_in_world_space(terrain, TerrainLod::Lod1)
+                .map_err(|e| format!("project far terrain: {e}"))?;
+        let far_nodes = assignments
+            .iter()
+            .filter(|a| a.lod == TerrainLod::Lod1)
+            .map(|a| Some(a.node_index))
+            .collect::<Vec<_>>();
+        ranges.extend(split_ranges(&mut far_mesh, &far_nodes, TerrainLod::Lod1)?);
+        let vertex_offset = u32::try_from(near_mesh.vertices.len())
+            .map_err(|_| "terrain LOD vertex offset exceeds u32".to_string())?;
+        let index_offset = u32::try_from(near_mesh.indices.len())
+            .map_err(|_| "terrain LOD index offset exceeds u32".to_string())?;
+        for index in &mut far_mesh.indices {
+            *index = index
+                .checked_add(vertex_offset)
+                .ok_or_else(|| "far terrain vertex index overflows".to_string())?;
+        }
+        for range in &mut far_mesh.draw_ranges {
+            range.first_index = range
+                .first_index
+                .checked_add(index_offset)
+                .ok_or_else(|| "far terrain draw range overflows".to_string())?;
+        }
+        near_mesh.vertices.extend(far_mesh.vertices);
+        near_mesh.indices.extend(far_mesh.indices);
+        near_mesh.draw_ranges.extend(far_mesh.draw_ranges);
+    }
+    Ok((near_mesh, Some(TerrainLodDraws { plan, ranges })))
+}
+
+fn split_ranges(
+    mesh: &mut VulkanStaticMesh,
+    nodes: &[Option<usize>],
+    lod: TerrainLod,
+) -> Result<Vec<(Option<usize>, TerrainLod)>, String> {
+    if mesh.indices.len() / 3 != nodes.len() || !mesh.indices.len().is_multiple_of(3) {
+        return Err("terrain LOD triangle metadata does not match the index buffer".to_string());
+    }
+    let mut ranges = Vec::<VulkanStaticDrawRange>::new();
+    let mut bindings = Vec::new();
+    for &range in &mesh.draw_ranges {
+        if !range.first_index.is_multiple_of(3) || !range.index_count.is_multiple_of(3) {
+            return Err("terrain LOD range is not triangle aligned".to_string());
+        }
+        let first = range.first_index as usize / 3;
+        let end = first
+            .checked_add(range.index_count as usize / 3)
+            .filter(|&end| end <= nodes.len())
+            .ok_or_else(|| "terrain LOD range is outside triangle metadata".to_string())?;
+        let mut start = first;
+        while start < end {
+            let node = nodes[start];
+            let mut next = start + 1;
+            while next < end && nodes[next] == node {
+                next += 1;
+            }
+            let mut split = range;
+            split.first_index =
+                u32::try_from(start * 3).map_err(|_| "terrain LOD index overflows".to_string())?;
+            split.index_count = u32::try_from((next - start) * 3)
+                .map_err(|_| "terrain LOD count overflows".to_string())?;
+            ranges.push(split);
+            bindings.push((node, lod));
+            start = next;
+        }
+    }
+    mesh.draw_ranges = ranges;
+    Ok(bindings)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use fparkan_render_vulkan::VulkanStaticVertex;
+
+    #[test]
+    #[ignore = "requires licensed GOG Constructor resources"]
+    fn gog_constructor_lod0_cells_match_native_basement_mask() {
+        use fparkan_runtime::*;
+        use std::{num::NonZeroUsize, sync::Arc};
+        let root = std::env::var_os("FPARKAN_GAME_ROOT")
+            .map(std::path::PathBuf::from)
+            .unwrap_or_else(|| std::path::PathBuf::from(r"C:\GOG Games\Parkan - Iron Strategy"));
+        let mut engine = create(EngineServices::new(Arc::new(
+            fparkan_vfs::DirectoryVfs::new(root),
+        )))
+        .unwrap();
+        load_mission_static_preview_roots(
+            &mut engine,
+            MissionRequest {
+                key: r"MISSIONS\CAMPAIGN\CAMPAIGN.00\Mission.02\data.tma".to_string(),
+                mode: MissionMode::SingleMission,
+            },
+            NonZeroUsize::new(usize::MAX).unwrap(),
+        )
+        .unwrap();
+        let assets = loaded_mission_assets(&engine).unwrap();
+        let roots = loaded_mission_object_drafts(&engine).unwrap();
+        let terrain = loaded_terrain(&engine).unwrap().source_mesh().unwrap();
+        let footprints = super::super::mission_basement_footprints(assets, roots).unwrap();
+        let borrowed = footprints
+            .iter()
+            .map(|f| fparkan_terrain::BasementFootprint {
+                outer: &f.outer,
+                inner: &f.inner,
+                flatten_inner_to_mean_outer_z: f.flatten_inner_to_mean_outer_z,
+            })
+            .collect::<Vec<_>>();
+        let mut foundation =
+            fparkan_terrain::build_basement_foundations(terrain, &borrowed).unwrap();
+        let source =
+            fparkan_render_vulkan::project_land_msh_to_static_mesh_in_world_space(terrain).unwrap();
+        let (near, _) =
+            super::super::project_basement_foundation(terrain, &source, &mut foundation).unwrap();
+        let plan = TerrainLodPlan::new(terrain, Some(&foundation)).unwrap();
+        let forced = (0..terrain.nodes_raw.len() / 38)
+            .filter(|&node| plan.selected_lod(node, [-10_000.0; 2], 1.3) == Some(TerrainLod::Lod0))
+            .collect::<Vec<_>>();
+        // GOG Terrain.dll (hash in original-binaries.md), live Render +0x11A19:
+        // cells whose patch list at Render-this +0x7A30 has a nonzero count.
+        assert_eq!(
+            forced,
+            [
+                54, 55, 56, 57, 70, 71, 72, 73, 86, 87, 113, 114, 115, 129, 130, 131, 146, 147,
+                183, 184, 199, 200
+            ]
+        );
+        let (mesh, draws) = prepare(terrain, near, Some(&foundation)).unwrap();
+        let draws = draws.unwrap();
+        let mut checked = [false; 2];
+        for (range, &(node, lod)) in draws.ranges.iter().enumerate() {
+            if node != Some(40) {
+                continue;
+            }
+            let count = mesh.draw_ranges[range].index_count;
+            // Native cell 40 selects far at camera cell [2, 5], near at [2, 7].
+            assert_eq!(
+                draws
+                    .index_count(range, count, [300.42047, 556.282, 155.91914], 1.3)
+                    .unwrap(),
+                if lod == TerrainLod::Lod1 { count } else { 0 }
+            );
+            assert_eq!(
+                draws
+                    .index_count(range, count, [265.0, 795.0, 155.91914], 1.3)
+                    .unwrap(),
+                if lod == TerrainLod::Lod0 { count } else { 0 }
+            );
+            checked[usize::from(lod == TerrainLod::Lod1)] = true;
+        }
+        assert_eq!(checked, [true, true]);
+    }
+
+    #[test]
+    fn cell_ranges_keep_material_state_and_separate_generated_bands() {
+        let range = VulkanStaticDrawRange {
+            first_index: 0,
+            index_count: 12,
+            material_index: 7,
+            lightmap_index: u8::MAX,
+            batch_flags: 0,
+            terrain_base_only: true,
+            pipeline_state: super::super::world_pipeline_state(
+                fparkan_render::LegacyBlendMode::Opaque,
+                fparkan_render::LegacyDepthMode::TestWrite,
+            ),
+            alpha_test_reference: VulkanStaticDrawRange::NATIVE_DEFAULT_ALPHA_TEST_REFERENCE,
+        };
+        let mut mesh = VulkanStaticMesh {
+            vertices: [[0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]
+                .map(|position| VulkanStaticVertex {
+                    position,
+                    color: [1.0; 3],
+                    normal: [0.0, 0.0, 1.0],
+                    uv: [0.0; 2],
+                    detail_uv: [0.0; 2],
+                    overlay_alpha: 0.0,
+                })
+                .to_vec(),
+            indices: vec![0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2],
+            draw_ranges: vec![range],
+        };
+        let nodes = [Some(4), Some(4), None, Some(5)];
+        let bindings = split_ranges(&mut mesh, &nodes, TerrainLod::Lod0).unwrap();
+        assert_eq!(
+            bindings,
+            vec![
+                (Some(4), TerrainLod::Lod0),
+                (None, TerrainLod::Lod0),
+                (Some(5), TerrainLod::Lod0)
+            ]
+        );
+        assert_eq!(
+            mesh.draw_ranges
+                .iter()
+                .map(|r| (r.first_index, r.index_count))
+                .collect::<Vec<_>>(),
+            vec![(0, 6), (6, 3), (9, 3)]
+        );
+        for split in &mesh.draw_ranges {
+            assert_eq!(split.material_index, 7);
+            assert_eq!(split.pipeline_state, range.pipeline_state);
+            assert!(split.terrain_base_only);
+        }
+        assert!(split_ranges(&mut mesh, &nodes[..3], TerrainLod::Lod0).is_err());
+    }
+}

crates/fparkan-terrain-format/src/lib.rs

@@ -226,6 +226,8 @@ pub enum TerrainLodError {
     DuplicateFaceAssignment { face: usize },
     /// A source face is absent from every supported terrain slot.
     MissingFaceAssignment { face: usize },
+    /// Slot bounds do not form the regular XY cell grid used by terrain rendering.
+    InvalidCellGrid,
     /// A checked index calculation overflowed.
     IntegerOverflow,
 }
@@ -276,6 +278,7 @@ impl std::fmt::Display for TerrainLodError {
             Self::MissingFaceAssignment { face } => {
                 write!(f, "terrain face {face} is not assigned to a supported slot")
             }
+            Self::InvalidCellGrid => write!(f, "terrain slots do not form a regular XY cell grid"),
             Self::IntegerOverflow => write!(f, "terrain slot index overflow"),
         }
     }

crates/fparkan-terrain/src/lib.rs

@@ -6,6 +6,9 @@ use std::collections::VecDeque;
 
 mod contour;
 mod foundation;
+mod lod;
+
+pub use lod::TerrainLodPlan;
 
 use foundation::basement_surface_mask;
 pub use foundation::{
@@ -1632,6 +1635,83 @@ mod tests {
         }
     }
 
+    #[test]
+    fn lod_grid_uses_authored_face_ownership_and_pins_changed_foundation_cells() {
+        use fparkan_terrain_format::{TerrainStream, TerrainStreamAttributes};
+        let mut mesh = synthetic_land_mesh();
+        mesh.faces.extend(mesh.faces.clone());
+        assign_terrain_lod_slots(&mut mesh, &[[0, 1]], &[[0, 2], [2, 2]]);
+        mesh.slots.header_raw = vec![0; 0x8c];
+        mesh.streams.push(TerrainStream {
+            type_id: 1,
+            attributes: TerrainStreamAttributes {
+                attr1: 1,
+                attr2: 1,
+                attr3: 0,
+            },
+            size: 38,
+        });
+        for slot in &mut mesh.slots.slots_raw {
+            slot[20..24].copy_from_slice(&1.0_f32.to_le_bytes());
+            slot[24..28].copy_from_slice(&1.0_f32.to_le_bytes());
+        }
+        let mut foundation = BasementFoundation {
+            placements: Vec::new(),
+            fragments: (0..2)
+                .map(|face| BasementFoundationFragment {
+                    source_face: Some(face),
+                    surface_mask: mesh.faces[face].flags,
+                    positions: mesh.faces[face]
+                        .vertices
+                        .map(|v| mesh.positions[usize::from(v)]),
+                })
+                .collect(),
+        };
+        foundation.fragments[0].positions.rotate_left(1);
+        let plan = TerrainLodPlan::new(&mesh, Some(&foundation)).unwrap();
+        assert_eq!(plan.source_face_node(3), Some(0));
+        assert_eq!(plan.source_face_node(4), None);
+        assert_eq!(
+            plan.selected_lod(0, [4.0, 4.0], 1.3),
+            Some(TerrainLod::Lod1)
+        );
+        foundation.fragments.pop();
+        let patched = TerrainLodPlan::new(&mesh, Some(&foundation)).unwrap();
+        assert_eq!(
+            patched.selected_lod(0, [4.0, 4.0], 1.3),
+            Some(TerrainLod::Lod0)
+        );
+        mesh.slots.slots_raw[0][24..28].copy_from_slice(&f32::NAN.to_le_bytes());
+        assert!(matches!(
+            TerrainLodPlan::new(&mesh, None),
+            Err(TerrainLodError::InvalidCellGrid)
+        ));
+    }
+
+    #[test]
+    #[ignore = "requires licensed corpus"]
+    fn licensed_corpus_land_meshes_build_native_lod_grids() {
+        let mut files = 0;
+        for path in files_under(&corpus_root("IS")) {
+            if !path
+                .file_name()
+                .and_then(|s| s.to_str())
+                .is_some_and(|s| s.eq_ignore_ascii_case("Land.msh"))
+            {
+                continue;
+            }
+            let bytes = std::fs::read(&path).unwrap();
+            let nres =
+                fparkan_nres::decode(Arc::from(bytes.into_boxed_slice()), ReadProfile::Compatible)
+                    .unwrap();
+            let mesh = fparkan_terrain_format::decode_land_msh(&nres).unwrap();
+            let plan = TerrainLodPlan::new(&mesh, None).unwrap_or_else(|e| panic!("{path:?}: {e}"));
+            assert!(plan.has_far_geometry(), "{path:?}: no far slots");
+            files += 1;
+        }
+        assert_eq!(files, 33, "original game LOD grid count");
+    }
+
     #[test]
     #[ignore = "requires licensed corpus"]
     fn licensed_corpus_land_meshes_build_surface_worlds() {

crates/fparkan-terrain/src/lod.rs

@@ -0,0 +1,301 @@
+use crate::{BasementFoundation, TerrainLod, TerrainLodError};
+use fparkan_terrain_format::LandMeshDocument;
+
+/// Camera-dependent terrain detail selection, retaining LOD0 in basement cells.
+#[derive(Clone, Debug)]
+pub struct TerrainLodPlan {
+    origin: [f32; 2],
+    inverse_cell_size: [f32; 2],
+    counts: [usize; 2],
+    forced_lod0: Vec<bool>,
+    has_lod1: Vec<bool>,
+    face_nodes: Vec<usize>,
+}
+
+impl TerrainLodPlan {
+    /// Validates the authored grid and registers foundation patches in its cells.
+    ///
+    /// # Errors
+    /// Returns an error for an invalid slot mapping, grid or foundation source face.
+    pub fn new(
+        mesh: &LandMeshDocument,
+        foundation: Option<&BasementFoundation>,
+    ) -> Result<Self, TerrainLodError> {
+        let assignments = mesh.face_lod_assignments()?;
+        let bounds = mesh
+            .nodes_raw
+            .chunks_exact(38)
+            .map(|node| {
+                let slot = u16::from_le_bytes([node[8], node[9]]);
+                let raw = mesh.slots.slots_raw.get(usize::from(slot))?;
+                let coordinate =
+                    |offset: usize| f32::from_le_bytes(raw[offset..offset + 4].try_into().unwrap());
+                Some((
+                    [coordinate(8), coordinate(12)],
+                    [coordinate(20), coordinate(24)],
+                ))
+            })
+            .collect::<Option<Vec<_>>>()
+            .ok_or(TerrainLodError::InvalidCellGrid)?;
+        let &(first_min, first_max) = bounds.first().ok_or(TerrainLodError::InvalidCellGrid)?;
+        let header = &mesh.slots.header_raw;
+        let coordinate = |offset: usize| {
+            header
+                .get(offset..offset + 4)
+                .map(|bytes| f32::from_le_bytes(bytes.try_into().unwrap()))
+        };
+        let origin = [
+            coordinate(0).ok_or(TerrainLodError::InvalidCellGrid)?,
+            coordinate(4).ok_or(TerrainLodError::InvalidCellGrid)?,
+        ];
+        let size = [first_max[0] - first_min[0], first_max[1] - first_min[1]];
+        if !origin.iter().all(|value| value.is_finite())
+            || !size.iter().all(|value| value.is_finite() && *value > 0.0)
+        {
+            return Err(TerrainLodError::InvalidCellGrid);
+        }
+        let count_x = mesh
+            .streams
+            .iter()
+            .find(|s| s.type_id == 1)
+            .map(|s| s.attributes.attr2 as usize)
+            .ok_or(TerrainLodError::InvalidCellGrid)?;
+        if count_x == 0 || !bounds.len().is_multiple_of(count_x) {
+            return Err(TerrainLodError::InvalidCellGrid);
+        }
+        let count_y = bounds.len() / count_x;
+        let counts = [count_x, count_y];
+        for (node, &(min, max)) in bounds.iter().enumerate() {
+            let cell = [node / count_y, node % count_y];
+            for axis in 0..2 {
+                let expected = origin[axis] + cell[axis] as f32 * size[axis];
+                let tolerance = size[axis] * 1.0e-5;
+                if !min[axis].is_finite()
+                    || !max[axis].is_finite()
+                    || (min[axis] - expected).abs() > tolerance
+                    || (max[axis] - (expected + size[axis])).abs() > tolerance
+                {
+                    return Err(TerrainLodError::InvalidCellGrid);
+                }
+            }
+        }
+        let has_lod1 = mesh
+            .nodes_raw
+            .chunks_exact(38)
+            .map(|node| {
+                let slot = u16::from_le_bytes([node[10], node[11]]);
+                slot != 0xff
+                    && slot != u16::MAX
+                    && mesh
+                        .slots
+                        .slots_raw
+                        .get(usize::from(slot))
+                        .is_some_and(|raw| u16::from_le_bytes([raw[2], raw[3]]) != 0)
+            })
+            .collect();
+        let mut result = Self {
+            origin,
+            inverse_cell_size: size.map(f32::recip),
+            counts,
+            forced_lod0: vec![false; bounds.len()],
+            has_lod1,
+            face_nodes: assignments.iter().map(|a| a.node_index).collect(),
+        };
+        if let Some(foundation) = foundation {
+            let mut fragments = vec![0usize; mesh.faces.len()];
+            let mut unchanged = vec![false; mesh.faces.len()];
+            for fragment in &foundation.fragments {
+                if let Some(face_index) = fragment.source_face {
+                    let face = mesh
+                        .faces
+                        .get(face_index)
+                        .ok_or(TerrainLodError::MissingFaceAssignment { face: face_index })?;
+                    fragments[face_index] += 1;
+                    let original = face.vertices.map(|v| mesh.positions[usize::from(v)]);
+                    unchanged[face_index] = fragment.positions.iter().all(|p| original.contains(p));
+                }
+            }
+            for assignment in assignments.iter().filter(|a| a.lod == TerrainLod::Lod0) {
+                if fragments[assignment.face_index] != 1 || !unchanged[assignment.face_index] {
+                    result.forced_lod0[assignment.node_index] = true;
+                }
+            }
+            // Native registers patch triangles against every cell, including shared edges.
+            for fragment in foundation.fragments.iter().filter(|fragment| {
+                fragment
+                    .source_face
+                    .is_none_or(|face| fragments[face] != 1 || !unchanged[face])
+            }) {
+                for node in 0..bounds.len() {
+                    let cell = [node / count_y, node % count_y];
+                    let center = std::array::from_fn(|axis| {
+                        (cell[axis] as f32 + 0.5) * size[axis] + origin[axis]
+                    });
+                    if triangle_intersects_cell(
+                        fragment.positions,
+                        center,
+                        result.inverse_cell_size,
+                    ) {
+                        result.forced_lod0[node] = true;
+                    }
+                }
+            }
+        }
+        Ok(result)
+    }
+
+    /// Returns the cell named by the authored slot that owns a source face.
+    #[must_use]
+    pub fn source_face_node(&self, face: usize) -> Option<usize> {
+        self.face_nodes.get(face).copied()
+    }
+
+    fn camera_cell(&self, point: [f32; 2]) -> Option<[i32; 2]> {
+        let cell: [f32; 2] = std::array::from_fn(|axis| {
+            ((point[axis] - self.origin[axis]) * self.inverse_cell_size[axis]).floor()
+        });
+        cell.iter()
+            .all(|v| v.is_finite() && *v >= i32::MIN as f32 && *v < i32::MAX as f32)
+            .then(|| cell.map(|v| v as i32))
+    }
+
+    /// Selects LOD1 at a squared cell distance of at least nine, unless forced near.
+    /// Returns `None` for an invalid node, camera position or FOV.
+    #[must_use]
+    pub fn selected_lod(
+        &self,
+        node: usize,
+        eye: [f32; 2],
+        horizontal_fov: f32,
+    ) -> Option<TerrainLod> {
+        let forced = *self.forced_lod0.get(node)?;
+        let has_far = *self.has_lod1.get(node)?;
+        let camera = self.camera_cell(eye)?;
+        if !horizontal_fov.is_finite() || horizontal_fov <= 0.0 {
+            return None;
+        }
+        let dx = (node / self.counts[1]) as f64 - f64::from(camera[0]);
+        let dy = (node % self.counts[1]) as f64 - f64::from(camera[1]);
+        Some(
+            if !forced && has_far && horizontal_fov >= 0.5 && dx * dx + dy * dy >= 9.0 {
+                TerrainLod::Lod1
+            } else {
+                TerrainLod::Lod0
+            },
+        )
+    }
+
+    /// Whether the map contains any usable far slots.
+    #[must_use]
+    pub fn has_far_geometry(&self) -> bool {
+        self.has_lod1.iter().any(|&value| value)
+    }
+}
+
+fn triangle_intersects_cell(
+    triangle: [[f32; 3]; 3],
+    center: [f32; 2],
+    inverse_size: [f32; 2],
+) -> bool {
+    // Normalize in f32 before testing the native [-0.5, 0.5] box.
+    let points = triangle.map(|p| {
+        std::array::from_fn::<_, 2, _>(|axis| {
+            f64::from((p[axis] - center[axis]) * inverse_size[axis])
+        })
+    });
+    let edges = std::array::from_fn::<_, 3, _>(|i| {
+        let next = points[(i + 1) % 3];
+        [next[1] - points[i][1], points[i][0] - next[0]]
+    });
+    [[1.0, 0.0], [0.0, 1.0]]
+        .into_iter()
+        .chain(edges)
+        .all(|axis| {
+            let projections = points.map(|p| p[0] * axis[0] + p[1] * axis[1]);
+            let radius = 0.5 * (axis[0].abs() + axis[1].abs());
+            projections.iter().copied().fold(f64::INFINITY, f64::min) <= radius
+                && projections
+                    .iter()
+                    .copied()
+                    .fold(f64::NEG_INFINITY, f64::max)
+                    >= -radius
+        })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn patch_registration_keeps_native_normalization_and_triangle_edges() {
+        let size = f32::from_bits(0x42d4_15f5);
+        let center = [2.5 * size, 6.5 * size];
+        let edge = [
+            [3.0 * size, 6.0 * size, 0.0],
+            [3.0 * size, 7.0 * size, 0.0],
+            [4.0 * size, 6.0 * size, 0.0],
+        ];
+        // The authored boundary rounds outside this cell after native normalization.
+        assert!(!triangle_intersects_cell(edge, center, [size.recip(); 2]));
+        assert!(triangle_intersects_cell(
+            edge,
+            [3.5 * size, 6.5 * size],
+            [size.recip(); 2]
+        ));
+        assert!(!triangle_intersects_cell(
+            [[0.0, 0.0, 0.0], [2.0, 0.0, 0.0], [0.0, 2.0, 0.0]],
+            [1.75, 1.75],
+            [2.0; 2]
+        ));
+        assert!(triangle_intersects_cell(
+            [[0.0, 0.0, 0.0], [2.0, 0.0, 0.0], [0.0, 2.0, 0.0]],
+            [1.5, 1.0],
+            [2.0; 2]
+        ));
+    }
+
+    #[test]
+    fn native_cell_distance_boundary_zoom_and_basement_override() {
+        let mut plan = TerrainLodPlan {
+            origin: [0.0; 2],
+            inverse_cell_size: [1.0; 2],
+            counts: [8, 8],
+            forced_lod0: vec![false; 64],
+            has_lod1: vec![true; 64],
+            face_nodes: Vec::new(),
+        };
+        assert_eq!(
+            plan.selected_lod(2 * 8 + 2, [0.9, 0.9], 1.3),
+            Some(TerrainLod::Lod0)
+        );
+        assert_eq!(
+            plan.selected_lod(3 * 8, [0.9, 0.9], 1.3),
+            Some(TerrainLod::Lod1)
+        );
+        assert_eq!(
+            plan.selected_lod(3 * 8, [1.0, 0.9], 1.3),
+            Some(TerrainLod::Lod0)
+        );
+        assert_eq!(
+            plan.selected_lod(3 * 8, [0.9, 0.9], 0.49),
+            Some(TerrainLod::Lod0)
+        );
+        assert_eq!(
+            plan.selected_lod(3 * 8, [0.9, 0.9], 0.5),
+            Some(TerrainLod::Lod1)
+        );
+        plan.forced_lod0[3 * 8] = true;
+        assert_eq!(
+            plan.selected_lod(3 * 8, [0.9, 0.9], 1.3),
+            Some(TerrainLod::Lod0)
+        );
+        plan.has_lod1[7 * 8] = false;
+        assert_eq!(
+            plan.selected_lod(7 * 8, [0.9, 0.9], 1.3),
+            Some(TerrainLod::Lod0)
+        );
+        assert_eq!(plan.selected_lod(64, [0.0; 2], 1.3), None);
+        assert_eq!(plan.selected_lod(0, [f32::NAN, 0.0], 1.3), None);
+        assert_eq!(plan.selected_lod(0, [0.0; 2], f32::INFINITY), None);
+    }
+}

docs/tomes/05-render.md

@@ -1030,11 +1030,39 @@ Node38, а диапазоны граней — в 68-байтовых Slot68. В
 проверяются на единственное назначение, а выходящий за массив, повторный или
 неподдерживаемый диапазон считается ошибкой загрузки.
 
-Первый рендер карты, terrain-запросы высоты и пересечения, receiver-ы теней и
-обрезка контуром зданий используют только LOD0. Отбор сохраняет порядок
-исходных граней, а контурный проход отдельно переводит индекс спроецированной
-грани обратно в исходный. LOD1 пока не подставляется по расстоянию: такой
-переход не реализован.
+Рисуемый уровень выбирается по ячейкам, а не по расстоянию до отдельного
+треугольника. Начало сетки находится в первых двух float заголовка Slot68,
+размер ячейки — в границах первого слота LOD0. Атрибут 2 потока Node38 задаёт
+число ячеек по X; индекс ячейки равен `x * count_y + y`. Приложение проверяет,
+что границы всех слотов образуют эту регулярную сетку. Все 33 карты GOG
+проходят такую проверку, включая вырожденные грани на общей границе ячеек:
+принадлежность грани берётся из слота, а не угадывается по её центру.
+
+Координаты камеры переводятся в целые координаты сетки округлением вниз.
+Если `dx * dx + dy * dy >= 9` и горизонтальный FOV не меньше 0,5 радиана,
+выбирается LOD1. При увеличении масштаба, отсутствии дальнего слота или
+наличии геометрического patch остаётся LOD0. Камера за границей карты не
+прижимается к крайней ячейке для этого расчёта. Правило восстановлено по
+GOG `Terrain.dll` ([сборка и SHA-256](../reference/original-binaries.md)):
+`CLandscape::Render`, RVA `0x11340`, выбор уровня `0x11878–0x11A03`.
+Исполнение оригинала подтверждает выбор дальнего слота, а getter камеры
+`Ngi32.dll` RVA `0x4D960` возвращает именно FOV.
+
+Основания строений сохраняют подробную геометрию. Нативная регистрация
+patch (`Terrain.dll` RVA `0x12E20`) проверяет его треугольники против каждой
+ячейки через `mrnParaIntersectsPoly`. Поэтому учитываются и соседние ячейки,
+которых касается край треугольника. Перед проверкой координаты нормализуются
+в `f32` относительно центра ячейки; замена этой операции сравнением мировых
+границ меняет результат на общих рёбрах. На «Конструкторе» игнорируемый
+ресурсный тест сверяет все 22 ячейки с принудительным LOD0 с набором,
+полученным в живом оригинале.
+
+Vulkan получает оба уровня один раз. Диапазоны индексов разделены по
+материалу и исходной ячейке; на каждом кадре включается только выбранный
+уровень. Сгенерированные отмостки остаются включены. Terrain-запросы высоты
+и пересечения, receiver-ы теней и обрезка контуром зданий используют
+канонический LOD0. Отбор сохраняет порядок исходных граней, а контурный проход
+отдельно переводит индекс спроецированной грани обратно в исходный.
 
 ```rust
 let assignments = mesh.face_lod_assignments()?;
@@ -1052,9 +1080,10 @@ for (face, assignment) in mesh.faces.iter().zip(assignments.iter()) {
 исходные фрагменты рельефа вместе с треугольниками отмостки в одном наборе.
 `TerrainWorld::with_basement_foundation` принимает этот набор во владение и
 устанавливает те же координаты и маски в BVH высотных запросов и пересечений.
-Предпросмотр миссии на Vulkan пока строит только LOD0: связывание BAS-записей
-с этой подготовкой ещё не подключено, поэтому наличие API не означает, что
-геометрия миссии уже обрезана.
+Предпросмотр миссии связывает BAS-записи с этой подготовкой до загрузки
+материалов. Полученная поверхность общая для изображения, теней и запросов;
+поправка размещения основания один раз применяется к корню строения и его
+присоединённым компонентам.
 
 Внешнее кольцо должно лежать на области LOD0, а каждый его сегмент — оставаться
 покрытым текущей поверхностью. Непокрытый сегмент или пересекающиеся контуры