From f2f5081669bc70ae1c47cbc20a2ad523a5a81ae8 Mon Sep 17 00:00:00 2001
From: Stewart Allen <stewart.allen@gmail.com>
Date: Thu, 1 Jan 2026 13:06:44 -0500
Subject: [PATCH] add mesh:tool 3mf object output

---
 src/load/3mf.js  | 130 ++++++++++++++++++++++++++++++++++++++++++++++-
 src/mesh/api.js  |   7 +--
 src/mesh/work.js |   5 ++
 3 files changed, 138 insertions(+), 4 deletions(-)

diff --git a/src/load/3mf.js b/src/load/3mf.js
index bf392988..3a7554ac 100644
--- a/src/load/3mf.js
+++ b/src/load/3mf.js
@@ -212,6 +212,133 @@ function extractItems(records) {
     return outItems;
 }
 
+/**
+ * Export vertex array(s) to 3MF format
+ * @param {Array} recs - array of {file: string, varr: Float32Array} records
+ * @param {Object} options - encoding options
+ * @param {String} [options.unit='millimeter'] - unit of measurement
+ * @param {String} [options.title='Model'] - model title
+ * @returns {Promise<Blob>} 3MF file as a Blob
+ */
+export async function encode(recs, options = {}) {
+    const {
+        unit = 'millimeter',
+        title = 'Model'
+    } = options;
+
+    // Build the 3D model XML
+    let objectId = 1;
+    let resources = [];
+    let buildItems = [];
+
+    for (let rec of recs) {
+        let { file, varr } = rec;
+        let name = file || `object-${objectId}`;
+
+        // Extract unique vertices and build triangle indices
+        let vertices = [];
+        let triangles = [];
+        let vertexMap = new Map(); // map "x,y,z" -> vertex index
+        let vertexIndex = 0;
+
+        // Process triangles (every 9 floats = 3 vertices = 1 triangle)
+        for (let i = 0; i < varr.length; i += 9) {
+            let triIndices = [];
+
+            // Process 3 vertices per triangle
+            for (let j = 0; j < 3; j++) {
+                let vi = i + j * 3;
+                let x = varr[vi];
+                let y = varr[vi + 1];
+                let z = varr[vi + 2];
+
+                // Create vertex key for deduplication
+                let key = `${x},${y},${z}`;
+                let idx = vertexMap.get(key);
+
+                if (idx === undefined) {
+                    idx = vertexIndex++;
+                    vertexMap.set(key, idx);
+                    vertices.push({ x, y, z });
+                }
+
+                triIndices.push(idx);
+            }
+
+            triangles.push(triIndices);
+        }
+
+        // Generate object XML
+        let objectXml = [`    <object id="${objectId}" name="${name}" type="model">`];
+        objectXml.push('      <mesh>');
+        objectXml.push('        <vertices>');
+
+        for (let v of vertices) {
+            objectXml.push(`          <vertex x="${v.x}" y="${v.y}" z="${v.z}"/>`);
+        }
+
+        objectXml.push('        </vertices>');
+        objectXml.push('        <triangles>');
+
+        for (let tri of triangles) {
+            objectXml.push(`          <triangle v1="${tri[0]}" v2="${tri[1]}" v3="${tri[2]}"/>`);
+        }
+
+        objectXml.push('        </triangles>');
+        objectXml.push('      </mesh>');
+        objectXml.push('    </object>');
+
+        resources.push(objectXml.join('\n'));
+        buildItems.push(`    <item objectid="${objectId}"/>`);
+
+        objectId++;
+    }
+
+    // Construct the complete 3D model XML
+    let modelXml = [
+        '<?xml version="1.0" encoding="UTF-8"?>',
+        `<model unit="${unit}" xml:lang="en-US" xmlns="http://schemas.microsoft.com/3dmanufacturing/core/2015/02">`,
+        '  <resources>',
+        resources.join('\n'),
+        '  </resources>',
+        '  <build>',
+        buildItems.join('\n'),
+        '  </build>',
+        '</model>'
+    ].join('\n');
+
+    // Create [Content_Types].xml
+    let contentTypes = [
+        '<?xml version="1.0" encoding="UTF-8"?>',
+        '<Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">',
+        '  <Default Extension="rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>',
+        '  <Default Extension="model" ContentType="application/vnd.ms-package.3dmanufacturing-3dmodel+xml"/>',
+        '</Types>'
+    ].join('\n');
+
+    // Create _rels/.rels
+    let rels = [
+        '<?xml version="1.0" encoding="UTF-8"?>',
+        '<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">',
+        '  <Relationship Target="/3D/3dmodel.model" Id="rel0" Type="http://schemas.microsoft.com/3dmanufacturing/2013/01/3dmodel"/>',
+        '</Relationships>'
+    ].join('\n');
+
+    // Create ZIP archive
+    let zip = new JSZip();
+    zip.file('[Content_Types].xml', contentTypes);
+    zip.file('_rels/.rels', rels);
+    zip.file('3D/3dmodel.model', modelXml);
+
+    // Generate the 3MF file as a blob
+    return await zip.generateAsync({
+        type: "uint8array",
+        compression: 'DEFLATE',
+        compressionOptions: { level: 6 },
+        streamFiles: true
+    });
+}
+
 /**
  * @param {Object} data binary file
  * @returns {Array} vertex face array
@@ -229,4 +356,5 @@ export function parseAsync(data) {
         }
         resolve(extractItems(models));
     });
-}
\ No newline at end of file
+}
+
diff --git a/src/mesh/api.js b/src/mesh/api.js
index 080ab478..de17b7ac 100644
--- a/src/mesh/api.js
+++ b/src/mesh/api.js
@@ -1008,9 +1008,10 @@ let file = {
                     h.input({ id: "filename", value: "mesh_export" })
                 ]),
                 h.div([
-                    h.button({ _: "download OBJ", onclick() { doit('obj') } }),
-                    h.button({ _: "download STL", onclick() { doit('stl') } }),
-                    h.button({ _: "download STEP", onclick() { doit('step') } }),
+                    h.button({ _: "3MF", onclick() { doit('3mf') } }),
+                    h.button({ _: "OBJ", onclick() { doit('obj') } }),
+                    h.button({ _: "STL", onclick() { doit('stl') } }),
+                    h.button({ _: "STEP", onclick() { doit('step') } }),
                 ])
             ]) ]
         });
diff --git a/src/mesh/work.js b/src/mesh/work.js
index 091a0faa..ccbd0d54 100644
--- a/src/mesh/work.js
+++ b/src/mesh/work.js
@@ -17,6 +17,7 @@ import { CSG } from '../geo/csg.js';
 import { util } from './util.js';
 import { tool as meshTool } from './tool.js';
 import { meshToSTEPWithFaces } from '../load/step.js';
+import { encode as tmfEncode } from '../load/3mf.js';
 import { encode as objEncode } from '../load/obj.js';
 import { encode as stlEncode } from '../load/stl.js';
 
@@ -580,6 +581,10 @@ const file = {
                 return objEncode(recs, header);
             case "stl":
                 return stlEncode(recs, header);
+            case "3mf":
+                send.async();
+                tmfEncode(recs, header).then(data => send.done(data));
+                return;
             default:
                 throw `invalid format "${format}"`;
         }