DXF export: strokes as zero-width centerlines, a 3ds Max R12 linework preset, and one view direction in VPORT

crates/cad/src/lib.rs

@@ -277,6 +277,8 @@ pub struct DxfOptions {
     pub colors: ColorDepth,
     pub raster: RasterFormat,
     pub preserve: Preserve,
+    /// Write one zero-width centerline per stroked path, ignoring its fill and stroke outline.
+    pub centerline_strokes: bool,
     /// Alter Paths for Appearance: every stroke is written as the filled area it paints.
     pub alter_paths: bool,
     /// Type is written as glyph outlines (always with [`Preserve::Appearance`]).
@@ -297,6 +299,7 @@ impl Default for DxfOptions {
             colors: ColorDepth::default(),
             raster: RasterFormat::default(),
             preserve: Preserve::default(),
+            centerline_strokes: false,
             alter_paths: false,
             outline_text: false,
             region: Rect::ZERO,

crates/cad/src/scene.rs

@@ -457,21 +457,39 @@ impl<'a> Scene<'a> {
         if bp.elements().is_empty() {
             return;
         }
+        let centerline = self.o.centerline_strokes
+            && n.appearance
+                .items
+                .iter()
+                .any(|item| matches!(item, AppearanceItem::Stroke(st) if st.visible && st.width > 0.0 && st.width.is_finite()));
+        let mut wrote_centerline = false;
         for item in &n.appearance.items {
             match item {
+                AppearanceItem::Fill(_) if centerline => {}
                 AppearanceItem::Fill(f) if f.visible => {
                     if let Some(rgb) = self.paint_rgb(&f.paint) {
                         let style = self.style(rgb, f.opacity, None, None);
                         self.area(bp, rule, &style, false);
                     }
                 }
-                AppearanceItem::Stroke(st) if st.visible && st.width > 0.0 && st.width.is_finite() => self.stroke(bp, rule, st),
+                // One centerline per path, however many strokes it has.
+                AppearanceItem::Stroke(st) if st.visible && st.width > 0.0 && st.width.is_finite() && !(centerline && wrote_centerline) => {
+                    self.stroke(bp, rule, st, centerline);
+                    wrote_centerline |= centerline;
+                }
                 _ => {}
             }
         }
     }
 
-    fn stroke(&mut self, bp: &BezPath, rule: FillRule, st: &StrokeLayer) {
+    fn stroke(&mut self, bp: &BezPath, rule: FillRule, st: &StrokeLayer, centerline: bool) {
+        if centerline {
+            let Some(rgb) = self.paint_rgb(&st.paint) else { return };
+            let linetype = st.dash.as_ref().filter(|d| d.is_dashed()).map(|d| self.linetype(d));
+            let style = self.style(rgb, st.opacity, Some(0.0), linetype);
+            self.lines(bp, &style, 0.0);
+            return;
+        }
         let appearance = self.o.preserve == Preserve::Appearance;
         if appearance
             && st.brush.is_some()

crates/cad/src/tests.rs

@@ -125,6 +125,27 @@ fn every_version_declares_its_acadver_and_is_well_formed() {
     assert_eq!(DxfVersion::from_id("2019"), None);
 }
 
+#[test]
+fn r12_viewport_has_no_duplicate_group_codes() {
+    let d = shapes_doc();
+    let out = export(&d, &DxfOptions { version: DxfVersion::R12, ..opts(&d) }).unwrap();
+    let vport = table(&out, "VPORT").into_iter().find(|o| kind(o) == "VPORT").expect("VPORT table record");
+    let codes: Vec<i32> = vport.iter().map(|pair| pair.0).collect();
+    let unique: std::collections::HashSet<_> = codes.iter().collect();
+    assert_eq!(unique.len(), codes.len(), "R12 VPORT record has duplicate group codes: {vport:?}");
+    let z = vport.iter().find(|pair| pair.0 == 36).map(|pair| pair.1.trim().parse::<f64>().unwrap());
+    assert_eq!(z, Some(1.0), "the view direction looks down the z axis");
+}
+
+#[test]
+fn centerline_strokes_write_one_line_per_stroked_path_and_no_fill() {
+    let d = shapes_doc();
+    let out = export(&d, &DxfOptions { centerline_strokes: true, ..opts(&d) }).unwrap();
+    let k = kinds(&out);
+    assert!(k.iter().all(|kind| kind != "HATCH"), "the stroked rectangle's fill is left out: {k:?}");
+    assert_eq!(k.len(), 2, "one centerline for each of the two stroked paths: {k:?}");
+}
+
 #[test]
 fn lines_are_lwpolylines_curves_splines_and_fills_hatches() {
     let d = shapes_doc();

crates/cad/src/writer.rs

@@ -441,7 +441,8 @@ impl Drawing {
         c.xy(13, 0.0, 0.0);
         c.xy(14, 1.0, 1.0);
         c.xy(15, 10.0, 10.0);
-        c.xyz(16, 0.0, 0.0);
+        // The view direction looks down the z axis: (0, 0, 1), each code once.
+        c.xy(16, 0.0, 0.0);
         c.num(36, 1.0);
         c.xyz(17, 0.0, 0.0);
         let (w, h) = ((x1 - x0).abs(), (y1 - y0).abs());

crates/engine/src/cmd/fileio/dxf.rs

@@ -21,7 +21,7 @@ pub fn specs() -> Vec<CommandSpec> {
         "Export DXF",
         [],
         None,
-        "{path?, version?: R12|R13|R14|2000|2004|2007|2010|2013|2018 (default), unit?: mm (default; any unit name: pt, in, cm…), scale?: 1 (drawing units per unit), scaleLineweights?: false, colors?: 8|16|256|true (default; true colour needs 2004+, else 256), rasterFormat?: png (default)|jpeg (placed images, written next to the file), preserve?: appearance (default: type as outlines; strokes a CAD line can't draw as filled outlines; brush art)|editability (type as text; every stroke a line with its lineweight and dashes), alterPaths?: false (every stroke as its filled outline), outlineText?: false, selectedOnly?: false (the selected objects, in their layers), artboard?: 0 (the origin is its bottom-left corner), useArtboards?: true (one drawing per chosen artboard, artboards?/range?, holding the art over it: {stem}-{artboard}.dxf) | false (the origin at the art's bounds)} → {path, bytes, warnings, files?, linked?: [image files]}; no path → {dataBase64, …, linked?: [{name, dataBase64}]}. Layers become DXF layers (hidden: off; locked; non-printing: not plotted); paths become polylines and splines, fills their outlines (which laser and cutter software reads) and solid hatches. Same as document.export {format: dxf}",
+        "{path?, version?: R12|R13|R14|2000|2004|2007|2010|2013|2018 (default), unit?: mm (default; any unit name: pt, in, cm…), scale?: 1 (drawing units per unit), scaleLineweights?: false, colors?: 8|16|256|true (default; true colour needs 2004+, else 256), rasterFormat?: png (default)|jpeg (placed images, written next to the file), preserve?: appearance (default: type as outlines; strokes a CAD line can't draw as filled outlines; brush art)|editability (type as text; every stroke a line with its lineweight and dashes), centerlineStrokes?: false (one zero-width centerline per stroked path; omits its fill), alterPaths?: false (every stroke as its filled outline), outlineText?: false, selectedOnly?: false (the selected objects, in their layers), artboard?: 0 (the origin is its bottom-left corner), useArtboards?: true (one drawing per chosen artboard, artboards?/range?, holding the art over it: {stem}-{artboard}.dxf) | false (the origin at the art's bounds)} → {path, bytes, warnings, files?, linked?: [image files]}; no path → {dataBase64, …, linked?: [{name, dataBase64}]}. Layers become DXF layers (hidden: off; locked; non-printing: not plotted); paths become polylines and splines, fills their outlines (which laser and cutter software reads) and solid hatches. Same as document.export {format: dxf}",
         has_doc,
         export_dxf
     )]
@@ -60,6 +60,12 @@ pub(super) const OPTIONS: &[FormatOption] = &[
         default: "\"appearance\"",
         description: "appearance (type as outlines, strokes a CAD line can't draw as filled outlines) or editability (type as text, strokes as lines)",
     },
+    FormatOption {
+        name: "centerlineStrokes",
+        ty: "boolean",
+        default: "false",
+        description: "one zero-width centerline per stroked path; omits the path's fill and stroke outline",
+    },
     FormatOption {
         name: "alterPaths",
         ty: "boolean",
@@ -121,6 +127,7 @@ struct Params {
     colors: Option<Value>,
     raster_format: Option<String>,
     preserve: Option<String>,
+    centerline_strokes: Option<bool>,
     alter_paths: Option<bool>,
     outline_text: Option<bool>,
 }
@@ -163,6 +170,7 @@ fn parse(p: &Value) -> Result<(DxfOptions, ArtboardPick)> {
         colors: choice("colors", q.colors.as_ref().map(text), ColorDepth::from_id, d.colors, "8, 16, 256 or true")?,
         raster: choice("rasterFormat", q.raster_format, RasterFormat::from_id, d.raster, "png or jpeg")?,
         preserve: choice("preserve", q.preserve, Preserve::from_id, d.preserve, "appearance or editability")?,
+        centerline_strokes: q.centerline_strokes.unwrap_or(d.centerline_strokes),
         alter_paths: q.alter_paths.unwrap_or(d.alter_paths),
         outline_text: q.outline_text.unwrap_or(d.outline_text),
         ..d

crates/ui-egui/src/dialogs/dxf_options.rs

@@ -1,6 +1,6 @@
 //! DXF Options (Export As → DXF): version, scale (1 unit of the art = N drawing units) and
 //! lineweights, number of colours, the format of placed images, Preserve Appearance or Maximize
-//! Editability, and Export Selected Art Only, Alter Paths for Appearance and Outline Text.
+//! Editability, centerline stroke output, Export Selected Art Only, Alter Paths for Appearance and Outline Text.
 //!
 //! Fields: `document.export` params (`format: dxf`, `path?`, the artboard choice) and the DXF
 //! options of `document.exportDxf`. OK remembers the options for next time and writes the file
@@ -42,6 +42,7 @@ fn defaults() -> Map<String, Value> {
         ("colors", json!(ColorDepth::default().id())),
         ("rasterFormat", json!(RasterFormat::default().id())),
         ("preserve", json!(Preserve::default().id())),
+        ("centerlineStrokes", json!(false)),
         ("alterPaths", json!(false)),
         ("outlineText", json!(false)),
         ("selectedOnly", json!(false)),
@@ -65,6 +66,18 @@ pub fn open(app: &mut VectorcraftApp, params: &Value) {
 }
 
 fn body(app: &mut VectorcraftApp, ui: &mut egui::Ui, d: &mut Dialog) -> bool {
+    if widgets::flat_button(ui, tl!("3ds Max — R12 Linework"), 210.0).clicked() {
+        d.fields.insert("version".into(), json!(DxfVersion::R12.id()));
+        d.fields.insert("unit".into(), json!(Unit::Millimeters.label()));
+        d.fields.insert("scale".into(), json!(1));
+        d.fields.insert("preserve".into(), json!(Preserve::Editability.id()));
+        d.fields.insert("centerlineStrokes".into(), json!(true));
+        d.fields.insert("colors".into(), json!(ColorDepth::Aci256.id()));
+        d.fields.insert("outlineText".into(), json!(true));
+        d.fields.insert("alterPaths".into(), json!(false));
+        d.fields.insert("scaleLineweights".into(), json!(false));
+    }
+    ui.add_space(6.0);
     let versions: Vec<(&str, &str)> = DxfVersion::ALL.iter().map(|v| (v.id(), v.label())).collect();
     choice(ui, d, "version", tl!("Version:"), &versions);
     ui.add_space(4.0);
@@ -99,6 +112,7 @@ fn body(app: &mut VectorcraftApp, ui: &mut egui::Ui, d: &mut Dialog) -> bool {
         d.fields.insert("selectedOnly".into(), json!(!d.bool("selectedOnly")));
     }
     check(ui, d, "alterPaths", tl!("Alter Paths for Appearance"));
+    check(ui, d, "centerlineStrokes", tl!("Export Strokes as Centerlines (0 width)"));
     // Preserve Appearance always outlines type.
     let appearance = preserve == Preserve::Appearance;
     if widgets::check(ui, tl!("Outline Text"), appearance || d.bool("outlineText"), !appearance) {
@@ -107,9 +121,13 @@ fn body(app: &mut VectorcraftApp, ui: &mut egui::Ui, d: &mut Dialog) -> bool {
     ui.add_space(8.0);
     super::form::caption(
         ui,
-        match preserve {
-            Preserve::Appearance => tl!("Type becomes outlines, and strokes a CAD line can't draw become filled shapes."),
-            Preserve::Editability => tl!("Type stays text, and every stroke is a line with its lineweight and dashes."),
+        if d.bool("centerlineStrokes") {
+            tl!("Stroked paths become one zero-width centerline; their fills are omitted.")
+        } else {
+            match preserve {
+                Preserve::Appearance => tl!("Type becomes outlines, and strokes a CAD line can't draw become filled shapes."),
+                Preserve::Editability => tl!("Type stays text, and every stroke is a line with its lineweight and dashes."),
+            }
         },
     );
     false

crates/ui-egui/src/i18n/cs.tsv

@@ -1906,6 +1906,9 @@ lighting	Light	Světlo
 	Scale to Fit Artboard	Přizpůsobit pracovní ploše
 	Scaling	Měřítko
 	Alter Paths for Appearance	Upravit cesty podle vzhledu
+	3ds Max — R12 Linework	Čárový výkres R12 pro 3ds Max
+	Export Strokes as Centerlines (0 width)	Exportovat tahy jako osy (tloušťka 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Cesty s tahem se změní na jednu osu nulové tloušťky; jejich výplně se vynechají.
 	DXF Options	Možnosti DXF
 	Export Option	Možnost exportu
 	Export Selected Art Only	Exportovat jen vybranou kresbu

crates/ui-egui/src/i18n/de.tsv

@@ -147,6 +147,9 @@
 	Alt	Alt
 	Alt:	Alt-Text:
 	Alter Paths for Appearance	Pfade für das Aussehen anpassen
+	3ds Max — R12 Linework	3ds Max — R12-Linien
+	Export Strokes as Centerlines (0 width)	Konturen als Mittellinien exportieren (Breite 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Pfade mit Kontur werden zu einer Mittellinie der Breite 0; ihre Flächen entfallen.
 	Amount	Stärke
 	Amount:	Stärke:
 	Anchor Point	Ankerpunkt

crates/ui-egui/src/i18n/es.tsv

@@ -165,6 +165,9 @@
 	Alt	Alt
 	Alt:	Alt:
 	Alter Paths for Appearance	Modificar trazados según la apariencia
+	3ds Max — R12 Linework	Trazado lineal R12 para 3ds Max
+	Export Strokes as Centerlines (0 width)	Exportar trazos como líneas centrales (grosor 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Los trazados con trazo se convierten en una línea central de grosor cero; se omiten sus rellenos.
 	Amount	Cantidad
 	Amount:	Cantidad:
 	Anchor Point	Punto de ancla

crates/ui-egui/src/i18n/fr.tsv

@@ -166,6 +166,9 @@
 	Alt	Alt
 	Alt:	Alt :
 	Alter Paths for Appearance	Modifier les tracés selon l’aspect
+	3ds Max — R12 Linework	3ds Max — Tracé linéaire R12
+	Export Strokes as Centerlines (0 width)	Exporter les contours en lignes médianes (épaisseur 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Les tracés avec contour deviennent une ligne médiane d’épaisseur nulle ; leurs fonds sont omis.
 	Amount	Quantité
 	Amount:	Quantité :
 	Anchor Point	Point d’ancrage

crates/ui-egui/src/i18n/hu.tsv

@@ -252,6 +252,10 @@
 	Alt+Drag	Alt+húzás
 	Alt:	Helyettesítő szöveg:
 	Alter Paths for Appearance	Útvonalak módosítása a megjelenés szerint
+	3ds Max — R12 Linework	3ds Max — R12 vonalrajz
+	Export Strokes as Centerlines (0 width)	Körvonalak exportálása középvonalként (0 vastagság)
+	Stroked paths become one zero-width centerline; their fills are omitted.	A körvonalas útvonalakból egyetlen 0 vastagságú középvonal lesz; a kitöltésük elmarad.
+	Ambient	Környezeti fény
 	Amount	Mérték
 	Amount:	Mérték:
 	Analogous	Analóg

crates/ui-egui/src/i18n/it.tsv

@@ -165,6 +165,9 @@
 	Alt	Alt
 	Alt:	Alt:
 	Alter Paths for Appearance	Modifica tracciati in base all'aspetto
+	3ds Max — R12 Linework	3ds Max — Linee R12
+	Export Strokes as Centerlines (0 width)	Esporta tracce come linee d’asse (spessore 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	I tracciati con traccia diventano un’unica linea d’asse a spessore zero; i riempimenti vengono omessi.
 	Amount	Quantità
 	Amount:	Quantità:
 	Anchor Point	Punto di ancoraggio

crates/ui-egui/src/i18n/ja.tsv

@@ -815,6 +815,9 @@
 	All the art	すべてのアート
 	Alt:	代替テキスト:
 	Alter Paths for Appearance	外観を保つためにパスを変更
+	3ds Max — R12 Linework	3ds Max — R12 線画
+	Export Strokes as Centerlines (0 width)	線を中心線として書き出し (幅 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	線のあるパスは幅 0 の中心線 1 本になり、塗りは省略されます。
 	Amount:	量:
 	Anchor Point	アンカーポイント
 	Anchor Point Tool	アンカーポイントツール

crates/ui-egui/src/i18n/ko.tsv

@@ -810,6 +810,9 @@
 	All the art	모든 아트워크
 	Alt:	Alt:
 	Alter Paths for Appearance	모양에 맞게 패스 변경
+	3ds Max — R12 Linework	3ds Max — R12 선 작업
+	Export Strokes as Centerlines (0 width)	선을 중심선으로 내보내기(두께 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	선이 있는 패스는 두께 0인 중심선 하나가 되며 칠은 생략됩니다.
 	Amount:	양:
 	Anchor Point	앵커 포인트
 	Anchor Point Tool	앵커 포인트 도구

crates/ui-egui/src/i18n/pl.tsv

@@ -1851,6 +1851,9 @@ lighting	Light	Światło
 	Scale to Fit Artboard	Skaluj, aby dopasować do obszaru kompozycji
 	Scaling	Skalowanie
 	Alter Paths for Appearance	Zmień ścieżki dla zachowania wyglądu
+	3ds Max — R12 Linework	3ds Max — linie R12
+	Export Strokes as Centerlines (0 width)	Eksportuj obrysy jako linie środkowe (szerokość 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Ścieżki z obrysem stają się jedną linią środkową o zerowej szerokości; ich wypełnienia są pomijane.
 	DXF Options	Opcje DXF
 	Export Option	Opcja eksportu
 	Export Selected Art Only	Eksportuj tylko zaznaczoną kompozycję

crates/ui-egui/src/i18n/pt-br.tsv

@@ -175,6 +175,7 @@
 	All the art	Toda a arte
 	Alt:	Alt:
 	Alter Paths for Appearance	Alterar Caminhos para Aparência
+	3ds Max — R12 Linework	Traçado em linhas R12 para 3ds Max
 	Amount:	Quantidade:
 	Anchor Point	Ponto de Ancoragem
 	Anchor Point Tool	Ferramenta Ponto de Ancoragem

crates/ui-egui/src/i18n/ru.tsv

@@ -163,6 +163,9 @@
 	Alt	Alt
 	Alt:	Alt:
 	Alter Paths for Appearance	Изменять контуры для оформления
+	3ds Max — R12 Linework	3ds Max — линии R12
+	Export Strokes as Centerlines (0 width)	Экспортировать обводки как осевые линии (толщина 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Контуры с обводкой становятся одной осевой линией нулевой толщины; заливки опускаются.
 	Amount	Количество
 	Amount:	Количество:
 	Anchor Point	Опорная точка

crates/ui-egui/src/i18n/uk.tsv

@@ -159,6 +159,9 @@
 	Alt	Alt
 	Alt:	Alt:
 	Alter Paths for Appearance	Змінювати контури для оформлення
+	3ds Max — R12 Linework	3ds Max — лінії R12
+	Export Strokes as Centerlines (0 width)	Експортувати обведення як осьові лінії (товщина 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Контури з обведенням стають однією осьовою лінією нульової товщини; заливки пропускаються.
 	Amount	Кількість
 	Amount:	Кількість:
 	Anchor Point	Опорна точка

crates/ui-egui/src/i18n/vi.tsv

@@ -191,6 +191,10 @@
 	Alt	Alt
 	Alt:	Alt:
 	Alter Paths for Appearance	Sửa đường dẫn cho diện mạo
+	3ds Max — R12 Linework	3ds Max — đường nét R12
+	Export Strokes as Centerlines (0 width)	Xuất nét thành đường tâm (độ rộng 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	Các đường có nét trở thành một đường tâm có độ rộng 0; phần tô của chúng bị bỏ qua.
+	Ambient	Ánh sáng môi trường
 	Amount	Mức độ
 	Amount:	Mức độ:
 	Anchor Point	Điểm neo

crates/ui-egui/src/i18n/zh-hans.tsv

@@ -125,6 +125,9 @@
 	Alt	Alt
 	Alt:	Alt：
 	Alter Paths for Appearance	为外观改变路径
+	3ds Max — R12 Linework	3ds Max — R12 线稿
+	Export Strokes as Centerlines (0 width)	将描边导出为中心线（宽度 0）
+	Stroked paths become one zero-width centerline; their fills are omitted.	带描边的路径变为一条宽度为零的中心线；其填色将被省略。
 	Amount	数量
 	Amount:	数量：
 	Anchor Point	锚点

crates/ui-egui/src/i18n/zh-hant.tsv

@@ -134,6 +134,9 @@
 	Alt	Alt
 	Alt:	Alt：
 	Alter Paths for Appearance	依外觀調整路徑
+	3ds Max — R12 Linework	3ds Max — R12 線稿
+	Export Strokes as Centerlines (0 width)	將筆畫轉存為中心線 (寬度 0)
+	Stroked paths become one zero-width centerline; their fills are omitted.	具有筆畫的路徑會變成一條寬度為零的中心線；其填色不會保留。
 	Amount	數量
 	Amount:	數量：
 	Anchor Point	錨點

docs/mcp.md

@@ -2277,6 +2277,14 @@ selected objects in their layers (every export takes it), and `useArtboards: tru
 artboard holding the art over it. What DXF can't hold (gradients and patterns as one colour, blending, opacity masks,
 raster effects, clipping) comes back in `warnings`.
 
+`centerlineStrokes: true` writes each stroked path once, as a zero-width centerline (its fill and stroke outline
+are left out): the linework 3D and CAM software extrude or sweep along, instead of the outline of the stroke's
+width. For linework intended for 3ds Max, Export As → DXF has a **3ds Max — R12 Linework** preset: millimetres, R12
+polylines (curves are flattened), editable strokes as centerlines, 256 colours and outlined text, the version older
+CAD importers read most reliably. Review the export warnings: R12 drops images and fill interiors. Through
+`document.exportDxf` the preset is `version: "R12"`, `unit: "mm"`, `preserve: "editability"`,
+`centerlineStrokes: true`, `colors: 256` and `outlineText: true`.
+
 DWG can't be written (no openly licensed writer exists): `document.formats` lists it under `unsupported` with that
 hint, and exporting to it answers with the hint to export DXF. PICT files are not supported either and say so when
 opened.