feat(scene): scale Solid3D / Region / Body tessellation by header FACETRES

ACIS-bearing entities tessellated with a hard-coded LOD ladder
(circ_segs / grid_u / grid_v) so a high-detail drawing produced the
same coarse mesh as a low-detail one. Multiply the per-LOD counts by
`header.facet_resolution` (FACETRES), clamped to AutoCAD's
documented [0.01, 10.0] range with a floor of 4 segments to keep
degenerate values harmless.

All four call sites (build_caches, commit_entity mesh seed, undo/redo
populate_meshes_from_document, and the helper signatures themselves)
take a FACETRES argument now.

ISOLINES / surface_u_density / surface_v_density and the
camera / sun / geo header fields stay metadata until matching render
work lands.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/scene/mod.rs

@@ -203,16 +203,19 @@ pub fn build_derived_caches(doc: &CadDocument) -> DerivedCaches {
         })
         .collect();
 
-    // meshes (parallel tessellation)
+    // meshes (parallel tessellation). FACETRES (header.facet_resolution)
+    // scales the per-LOD segment counts so users with finer drawings get
+    // smoother solids; clamped to AutoCAD's [0.01, 10.0] range inside.
+    let facet_res = doc.header.facet_resolution;
     let meshes: HashMap<Handle, MeshLodSet> = mesh_handles
         .par_iter()
         .filter_map(|&handle| {
             let e = doc.get_entity(handle)?;
             let color = tessellate::aci_to_rgba(&e.common().color);
             let model = match e {
-                EntityType::Solid3D(s) => solid3d_tess::tessellate_solid3d(s, color),
+                EntityType::Solid3D(s) => solid3d_tess::tessellate_solid3d(s, color, facet_res),
-                EntityType::Region(r) => solid3d_tess::tessellate_region(r, color),
+                EntityType::Region(r) => solid3d_tess::tessellate_region(r, color, facet_res),
-                EntityType::Body(b) => solid3d_tess::tessellate_body(b, color),
+                EntityType::Body(b) => solid3d_tess::tessellate_body(b, color, facet_res),
                 _ => None,
             };
             model.map(|m| (handle, m))
@@ -2372,18 +2375,19 @@ impl Scene {
         } else {
             None
         };
+        let facet_res = self.document.header.facet_resolution;
         let mesh_seed = match &entity {
             EntityType::Solid3D(s3d) => {
                 let color = self.render_style(&entity).0;
-                solid3d_tess::tessellate_solid3d(s3d, color)
+                solid3d_tess::tessellate_solid3d(s3d, color, facet_res)
             }
             EntityType::Region(r) => {
                 let color = self.render_style(&entity).0;
-                solid3d_tess::tessellate_region(r, color)
+                solid3d_tess::tessellate_region(r, color, facet_res)
             }
             EntityType::Body(b) => {
                 let color = self.render_style(&entity).0;
-                solid3d_tess::tessellate_body(b, color)
+                solid3d_tess::tessellate_body(b, color, facet_res)
             }
             _ => None,
         };
@@ -3216,13 +3220,16 @@ impl Scene {
             .collect();
 
         use rayon::prelude::*;
+        let facet_res = self.document.header.facet_resolution;
         self.meshes = entries
             .into_par_iter()
             .filter_map(|(handle, entity, color)| {
                 let model = match &entity {
-                    EntityType::Solid3D(s) => solid3d_tess::tessellate_solid3d(s, color),
+                    EntityType::Solid3D(s) => {
-                    EntityType::Region(r) => solid3d_tess::tessellate_region(r, color),
+                        solid3d_tess::tessellate_solid3d(s, color, facet_res)
-                    EntityType::Body(b) => solid3d_tess::tessellate_body(b, color),
+                    }
+                    EntityType::Region(r) => solid3d_tess::tessellate_region(r, color, facet_res),
+                    EntityType::Body(b) => solid3d_tess::tessellate_body(b, color, facet_res),
                     _ => None,
                 };
                 model.map(|m| (handle, m))

src/scene/solid3d_tess.rs

@@ -120,11 +120,13 @@ fn tessellate_sat_lods(
     sat: &SatDocument,
     name: String,
     color: [f32; 4],
+    facet_res: f64,
 ) -> Option<MeshLodSet> {
     let configs = LodConfig::all();
     let mut lods: Vec<MeshModel> = Vec::with_capacity(3);
     for lod in configs {
-        if let Some(m) = tessellate_sat(sat, name.clone(), color, lod) {
+        let scaled = scale_lod(lod, facet_res);
+        if let Some(m) = tessellate_sat(sat, name.clone(), color, scaled) {
             lods.push(m);
         }
     }
@@ -135,6 +137,18 @@ fn tessellate_sat_lods(
     Some(MeshLodSet { lods, world_aabb })
 }
 
+/// Scale a LOD's segment counts by FACETRES (clamped to AutoCAD's
+/// documented [0.01, 10.0] range). 1.0 is the unchanged baseline.
+fn scale_lod(base: LodConfig, facet_res: f64) -> LodConfig {
+    let m = (facet_res.clamp(0.01, 10.0) as f32).max(0.01);
+    let scale = |v: usize| ((v as f32) * m).round().max(4.0) as usize;
+    LodConfig {
+        circ_segs: scale(base.circ_segs),
+        grid_u: scale(base.grid_u),
+        grid_v: scale(base.grid_v),
+    }
+}
+
 /// World-XY AABB of the mesh — used by the render-pipeline LOD selector
 /// to pick a level based on projected pixel diagonal.
 fn mesh_aabb(mesh: &MeshModel) -> [f32; 4] {
@@ -169,39 +183,40 @@ fn parse_acis(
 }
 
 /// Tessellate a `Region` entity (2D planar ACIS body) at all three LOD levels.
-pub fn tessellate_region(region: &Region, color: [f32; 4]) -> Option<MeshLodSet> {
+pub fn tessellate_region(region: &Region, color: [f32; 4], facet_res: f64) -> Option<MeshLodSet> {
     let sat = parse_acis(
         || region.parse_sat(),
         region.acis_data.is_binary,
         &region.acis_data.sab_data,
     )?;
     let name = region.common.handle.value().to_string();
-    tessellate_sat_lods(&sat, name, color)
+    tessellate_sat_lods(&sat, name, color, facet_res)
 }
 
 /// Tessellate a `Body` entity (3D ACIS body) at all three LOD levels.
-pub fn tessellate_body(body: &Body, color: [f32; 4]) -> Option<MeshLodSet> {
+pub fn tessellate_body(body: &Body, color: [f32; 4], facet_res: f64) -> Option<MeshLodSet> {
     let sat = parse_acis(
         || body.parse_sat(),
         body.acis_data.is_binary,
         &body.acis_data.sab_data,
     )?;
     let name = body.common.handle.value().to_string();
-    tessellate_sat_lods(&sat, name, color)
+    tessellate_sat_lods(&sat, name, color, facet_res)
 }
 
 /// Tessellate a `Solid3D` entity at all three LOD levels.
 ///
 /// Returns `None` when the entity has no parseable SAT data or produces no
 /// triangles (e.g. the solid uses only unsupported surface types).
-pub fn tessellate_solid3d(solid: &Solid3D, color: [f32; 4]) -> Option<MeshLodSet> {
+/// `facet_res` mirrors the header FACETRES variable (0.01–10.0).
+pub fn tessellate_solid3d(solid: &Solid3D, color: [f32; 4], facet_res: f64) -> Option<MeshLodSet> {
     let sat = parse_acis(
         || solid.parse_sat(),
         solid.acis_data.is_binary,
         &solid.acis_data.sab_data,
     )?;
     let name = solid.common.handle.value().to_string();
-    tessellate_sat_lods(&sat, name, color)
+    tessellate_sat_lods(&sat, name, color, facet_res)
 }
 
 // ── Topology helpers ──────────────────────────────────────────────────────────