缩放后修复，合并有问题

.gitignore

@@ -1,3 +1,6 @@
 __pycache__
 uploads/*
-tmp/*
+tmp/*
+venv
+instance
+huey_queue.*

app/routes.py

@@ -9,7 +9,7 @@ from flask_login import login_user, logout_user, login_required, current_user
 from werkzeug.security import generate_password_hash, check_password_hash
 from werkzeug.utils import secure_filename
 from .models import db, User, PrintFile, SystemConfig
-from .tasks import merge_and_slice_task, slice_stl_task
+from .tasks import merge_and_slice_task, slice_stl_task, simplify_stl_task
 from app import i18n_dict
 # import trimesh.repair
 from stl_simplifier import simplify_stl
@@ -118,11 +118,14 @@ def files():
                 original_filename=original_filename,
                 file_type='stl',
                 user_id=current_user.id,
-                status='uploaded' # Only display as uploaded, no automatic slicing
+                status='simplifying' # Set to simplifying while proxy is generated
             )
             db.session.add(print_file)
             db.session.commit()
             
+            # Start background simplification
+            simplify_stl_task(print_file.id, filepath)
+            
             flash('File uploaded successfully!', 'success')
             return redirect(url_for('main.files'))
 
@@ -241,6 +244,7 @@ def settings():
         # concurrent_slices = request.form.get('concurrent_slices')
         offset_x = request.form.get('offset_x', '0')
         offset_y = request.form.get('offset_y', '0')
+        proxy_skip_size_mb = request.form.get('proxy_skip_size_mb', '5.0')
         default_infill = request.form.get('default_infill', '20')
         default_support = request.form.get('default_support', 'false')
         default_support_pattern = request.form.get('default_support_pattern', 'tree')
@@ -250,6 +254,7 @@ def settings():
         config_items = [
             ('offset_x', offset_x), 
             ('offset_y', offset_y),
+            ('proxy_skip_size_mb', proxy_skip_size_mb),
             ('default_infill', default_infill),
             ('default_support', default_support),
             ('default_support_pattern', default_support_pattern),
@@ -368,11 +373,6 @@ def serve_proxy_file(file_id):
         abort(403)
     path = os.path.join(current_app.config['UPLOAD_FOLDER'], f.filename)
     proxy_path = path + '.proxy.stl'
-    if not os.path.exists(proxy_path):
-        try:
-            simplify_stl(path, proxy_path, keep_ratio=0.05) # compress to 90%
-        except:
-            return send_file(path) # fallback to original if error
     if os.path.exists(proxy_path):
         return send_file(proxy_path)
     return send_file(path)
@@ -406,24 +406,53 @@ def merge_and_slice():
     else:
         combined_name += " 单独切片"
         
+    is_edit = data.get('is_edit', False)
+
     for p in pieces:
         f = PrintFile.query.get(p['file_id'])
         if f and (f.user_id == current_user.id or current_user.is_admin):
             path = os.path.join(current_app.config['UPLOAD_FOLDER'], f.filename)
             inputs.append((path, p['matrix']))
-            if 'raw_matrix' in p:
+            # 只有在单一编辑模式才修改原模型的矩阵 (如果多模型/新建模式，我们不修改原模型，而是后续记录到新的包含实体上)
+            if 'raw_matrix' in p and is_edit and len(pieces) == 1:
                 f.transform_matrix = json.dumps(p['raw_matrix'])
                 db.session.add(f)
 
     db.session.commit()
 
-    if len(inputs) == 0:
+    target_file_id = data.get('target_file_id')
-        return jsonify({'error': 'Invalid files'}), 400
 
-    is_edit = data.get('is_edit', False)
+    if is_edit and target_file_id:
-
+        print_file = PrintFile.query.get(target_file_id)
-    if len(inputs) == 1 and is_edit:
+        if not print_file:
-        # User is just generating gcode for a single original model, do NOT pollute list with new STL
+            return jsonify({'error': 'Original file not found'}), 404
+        print_file.status = 'merging'
+        
+        if print_file.transform_matrix and 'is_composite' in print_file.transform_matrix:
+            composite_data = {
+                "is_composite": True,
+                "parts": []
+            }
+            for p in pieces:
+                pf = PrintFile.query.get(p['file_id'])
+                if pf:
+                    composite_data['parts'].append({
+                        "file_id": pf.id,
+                        "name": pf.original_filename,
+                        "url": url_for('main.serve_proxy_file', file_id=pf.id),
+                        "raw_matrix": p.get('raw_matrix', p['matrix'])
+                    })
+            print_file.transform_matrix = json.dumps(composite_data)
+        elif len(pieces) == 1:
+            print_file.transform_matrix = json.dumps(pieces[0].get('raw_matrix', pieces[0]['matrix']))
+            
+        db.session.commit()
+        
+        temp_filename = f"temp_edit_{uuid.uuid4().hex}.stl"
+        temp_filepath = os.path.join(current_app.config['UPLOAD_FOLDER'], temp_filename)
+        
+        merge_and_slice_task(target_file_id, inputs, temp_filepath, quality, infill_density, support_enable, support_pattern, delete_stl=True)
+    elif len(inputs) == 1 and is_edit:
         target_file_id = pieces[0]['file_id']
         print_file = PrintFile.query.get(target_file_id)
         if not print_file:
@@ -442,12 +471,28 @@ def merge_and_slice():
         unique_filename = f"{timestamp}_{uuid.uuid4().hex}.stl"
         merged_filepath = os.path.join(current_app.config['UPLOAD_FOLDER'], unique_filename)
         
+        # 构建组合文件元数据树 (is_composite: true)
+        composite_data = {
+            "is_composite": True,
+            "parts": []
+        }
+        for p in pieces:
+            pf = PrintFile.query.get(p['file_id'])
+            if pf:
+                composite_data['parts'].append({
+                    "file_id": pf.id,
+                    "name": pf.original_filename,
+                    "url": url_for('main.serve_proxy_file', file_id=pf.id),
+                    "raw_matrix": p.get('raw_matrix', p['matrix'])
+                })
+        
         print_file = PrintFile(
             filename=unique_filename,
             original_filename=f"{combined_name}.stl",
             file_type='stl',
             user_id=current_user.id,
-            status='merging'
+            status='merging',
+            transform_matrix=json.dumps(composite_data)
         )
         db.session.add(print_file)
         db.session.commit()

app/tasks.py

@@ -238,3 +238,53 @@ def merge_and_slice_task(file_id, inputs, merged_filepath, quality_preset=None,
             app.logger.error(f"Merge Exception: {e}")
         finally:
             db.session.remove()
+
+@huey.task()
+def simplify_stl_task(file_id, filepath):
+    from app import create_app
+    app = create_app()
+    with app.app_context():
+        from .models import PrintFile, SystemConfig, db
+        import os
+        from stl_simplifier import simplify_stl
+        
+        print_file = PrintFile.query.get(file_id)
+        if not print_file:
+            return
+            
+        try:
+            file_size_mb = os.path.getsize(filepath) / (1024 * 1024)
+            
+            configs = {c.key: c.value for c in SystemConfig.query.all()}
+            skip_size = float(configs.get('proxy_skip_size_mb', '5.0'))
+            
+            proxy_path = filepath + '.proxy.stl'
+            
+            if file_size_mb <= skip_size:
+                # File is small enough, no proxy needed
+                print_file.status = 'uploaded'
+                db.session.commit()
+                return
+                
+            # Aim for approx 7.5 MB for the proxy
+            target_mb = 7.5
+            keep_ratio = target_mb / file_size_mb
+            if keep_ratio > 1.0:
+                keep_ratio = 1.0
+            elif keep_ratio < 0.01:
+                keep_ratio = 0.01
+                
+            app.logger.info(f"Simplifying {filepath}... Size: {file_size_mb:.2f}MB, Target Ratio: {keep_ratio:.3f}")
+            
+            simplify_stl(filepath, proxy_path, keep_ratio=keep_ratio)
+            
+        except Exception as e:
+            app.logger.error(f"Simplify task error: {e}")
+            
+        # Update status to uploaded regardless of success or failure of proxy generation
+        # So the user can still slice or download it
+        print_file = PrintFile.query.get(file_id)
+        if print_file:
+            print_file.status = 'uploaded'
+            db.session.commit()
+        db.session.remove()

app/templates/admin_settings.html

@@ -22,6 +22,12 @@
                 <div class="form-text">{{ _('Adjust the Y-axis compilation offset for combined files on the build plate.') }}</div>
             </div>
 
+            <div class="mb-3">
+                <label for="proxy_skip_size_mb" class="form-label">{{ _('Proxy Skip Size (MB)') }}</label>
+                <input type="number" class="form-control" name="proxy_skip_size_mb" id="proxy_skip_size_mb" value="{{ configs.get('proxy_skip_size_mb', '5.0') }}" step="0.1" min="0">
+                <div class="form-text">{{ _('Files smaller than this will not generate a simplified proxy.') }}</div>
+            </div>
+
             <h5 class="mt-4">{{ _('Default Plater Settings') }}</h5>
             <hr>
             

app/templates/files.html

@@ -40,11 +40,16 @@
                 <tbody>
                     {% for file in files %}
                     <tr id="file-row-{{ file.id }}" data-status="{{ file.status }}">
-                        <td class="ps-4 text-muted"><i class="bi bi-clock me-1"></i>{{ file.created_at.strftime('%Y-%m-%d %H:%M:%S') }}</td>
+                        <td class="ps-4 text-muted">
+                            <i class="bi bi-clock me-1"></i>
+                            <span class="local-time" data-utc="{{ file.created_at.isoformat() }}">{{ file.created_at.strftime('%Y-%m-%d %H:%M:%S') }}</span>
+                        </td>
                         <td class="fw-medium">{{ file.original_filename }}</td>
                         <td id="status-{{ file.id }}">
                             {% if file.status == 'waiting' %}
                                 <span class="badge bg-info text-dark rounded-pill fw-normal px-2" title="{{ _('Waiting in queue for slicing') }}"><i class="bi bi-hourglass-split me-1"></i>{{ _('Waiting') }}...</span>
+                            {% elif file.status == 'simplifying' %}
+                                <span class="badge bg-secondary text-dark rounded-pill fw-normal px-2" style="background-color: #e2e3e5 !important;"><i class="bi bi-funnel bi-spin me-1"></i>{{ _('Simplifying') }}...</span>
                             {% elif file.status == 'uploaded' %}
                                 <span class="badge bg-secondary text-light rounded-pill fw-normal px-2"><i class="bi bi-cloud-check me-1"></i>{{ _('Uploaded') }}</span>
                             {% elif file.status == 'merging' %}
@@ -86,6 +91,25 @@
 
 <script>
 document.addEventListener('DOMContentLoaded', function() {
+    // Convert UTC to local time
+    document.querySelectorAll('.local-time').forEach(el => {
+        let utcStr = el.getAttribute('data-utc');
+        if (!utcStr) return;
+        if (!utcStr.endsWith('Z') && !utcStr.includes('+')) {
+            utcStr += 'Z';
+        }
+        const localDate = new Date(utcStr);
+        if (!isNaN(localDate)) {
+            const year = localDate.getFullYear();
+            const month = String(localDate.getMonth() + 1).padStart(2, '0');
+            const day = String(localDate.getDate()).padStart(2, '0');
+            const hours = String(localDate.getHours()).padStart(2, '0');
+            const minutes = String(localDate.getMinutes()).padStart(2, '0');
+            const seconds = String(localDate.getSeconds()).padStart(2, '0');
+            el.textContent = `${year}-${month}-${day} ${hours}:${minutes}:${seconds}`;
+        }
+    });
+
     const checkInterval = 1000;
     let pollTimer = null;
     
@@ -105,6 +129,7 @@ document.addEventListener('DOMContentLoaded', function() {
                         const actionsTd = document.getElementById('actions-container-' + id);
                         
                         if (status === 'waiting') statusTd.innerHTML = '<span class="badge bg-info text-dark rounded-pill fw-normal px-2"><i class="bi bi-hourglass-split me-1"></i>{{ _("Waiting") }}...</span>';
+                        else if (status === 'simplifying') statusTd.innerHTML = '<span class="badge bg-secondary text-dark rounded-pill fw-normal px-2" style="background-color: #e2e3e5 !important;"><i class="bi bi-funnel bi-spin me-1"></i>{{ _("Simplifying") }}...</span>';
                         else if (status === 'uploaded') statusTd.innerHTML = '<span class="badge bg-secondary text-light rounded-pill fw-normal px-2"><i class="bi bi-cloud-check me-1"></i>{{ _("Uploaded") }}</span>';
                         else if (status === 'merging') statusTd.innerHTML = '<span class="badge bg-primary text-light rounded-pill fw-normal px-2"><i class="bi bi-intersect me-1"></i>{{ _("Merging") }}...</span>';
                         else if (status === 'slicing') statusTd.innerHTML = '<span class="badge bg-warning text-dark rounded-pill fw-normal px-2"><i class="bi bi-gear-wide-connected bi-spin me-1"></i>{{ _("Slicing") }}...</span>';
@@ -128,7 +153,7 @@ document.addEventListener('DOMContentLoaded', function() {
                         actionsTd.innerHTML = actionsHtml;
                     }
                     
-                    if (status === 'waiting' || status === 'slicing' || status === 'merging') {
+                    if (status === 'waiting' || status === 'slicing' || status === 'merging' || status === 'simplifying') {
                         hasPending = true;
                     }
                 }

app/templates/plater.html

@@ -480,14 +480,59 @@ function clearPlate() {
 }
 
 function addModelToPlate(btnElement, fileId, url, name, status) {
-    const iconSpan = btnElement.querySelector('i');
+    let matrixData = btnElement ? btnElement.getAttribute('data-matrix') : null;
-    const originalClass = iconSpan.className;
+    
-    iconSpan.className = 'spinner-border spinner-border-sm text-primary';
+    if (matrixData && matrixData.includes('"is_composite"')) {
-    btnElement.disabled = true;
+        try {
+            let comp = JSON.parse(matrixData);
+            if (comp.is_composite && comp.parts) {
+                if (btnElement) {
+                    const iconSpan = btnElement.querySelector('i');
+                    const originalClass = iconSpan.className;
+                    iconSpan.className = 'spinner-border spinner-border-sm text-primary';
+                    btnElement.disabled = true;
+                    
+                    let totalParts = comp.parts.length;
+                    let loadedCount = 0;
+                    
+                    comp.parts.forEach(part => {
+                        loadSTL(part.file_id, part.url, part.name, 'uploaded', JSON.stringify(part.raw_matrix), () => {
+                            loadedCount++;
+                            if (loadedCount === totalParts) {
+                                iconSpan.className = originalClass;
+                                btnElement.disabled = false;
+                            }
+                        });
+                    });
+                } else {
+                    comp.parts.forEach(part => {
+                        loadSTL(part.file_id, part.url, part.name, 'uploaded', JSON.stringify(part.raw_matrix));
+                    });
+                }
+                return;
+            }
+        } catch (e) {
+            console.error(e);
+        }
+    }
+    
+    if (btnElement) {
+        const iconSpan = btnElement.querySelector('i');
+        const originalClass = iconSpan.className;
+        iconSpan.className = 'spinner-border spinner-border-sm text-primary';
+        btnElement.disabled = true;
+        loadSTL(fileId, url, name, status, matrixData, () => {
+            iconSpan.className = originalClass;
+            btnElement.disabled = false;
+        });
+    } else {
+        loadSTL(fileId, url, name, status, matrixData);
+    }
+}
 
+function loadSTL(fileId, url, name, status, matrixData, callback) {
     const loader = new THREE.STLLoader();
     loader.load(url, function (geometry) {
-        // By default STLs center or are offset, let's normalize slightly to be on top of the plate
         geometry.computeBoundingBox();
         const center = geometry.boundingBox.getCenter(new THREE.Vector3());
         const minZ = geometry.boundingBox.min.z;
@@ -502,8 +547,7 @@ function addModelToPlate(btnElement, fileId, url, name, status) {
             geomTrans: new THREE.Matrix4().makeTranslation(-center.x, -center.y, -minZ)
         };
         
-        let matrixData = btnElement.getAttribute('data-matrix');
+        if (matrixData && matrixData.trim() !== '' && matrixData !== 'None' && !matrixData.includes('"is_composite"')) {
-        if (matrixData && matrixData.trim() !== '' && matrixData !== 'None') {
             try {
                 let mArray = JSON.parse(matrixData);
                 let savedMatrix = new THREE.Matrix4().fromArray(mArray);
@@ -514,7 +558,6 @@ function addModelToPlate(btnElement, fileId, url, name, status) {
                 mesh.position.y = (Math.random() - 0.5) * 50;
             }
         } else {
-            // Random slight offset so they don't exactly stack
             mesh.position.x = (Math.random() - 0.5) * 50;
             mesh.position.y = (Math.random() - 0.5) * 50;
         }
@@ -522,13 +565,11 @@ function addModelToPlate(btnElement, fileId, url, name, status) {
         scene.add(mesh);
         loadedModels.push(mesh);
         selectModel(mesh);
-
+        
-        iconSpan.className = originalClass;
+        if (callback) callback();
-        btnElement.disabled = false;
     }, undefined, function (error) {
         console.error(error);
-        iconSpan.className = originalClass;
+        if (callback) callback();
-        btnElement.disabled = false;
         alert("{{ _('Error loading STL model file.') }}");
     });
 }
@@ -581,6 +622,8 @@ function animate() {
 }
 
 function mergeAndSlice() {
+    selectModel(null); // Detach any active model to bake transformProxy world coordinates into its local matrix properties
+    
     if (loadedModels.length === 0) {
         alert("{{ _('Please add at least one model to the build plate.') }}");
         return;
@@ -591,14 +634,27 @@ function mergeAndSlice() {
         return;
     }
     
-    let isEdit = (loadedModels.length === 1 && String(loadedModels[0].userData.fileId) === String(initialAddId));
+    let isEdit = false;
+    let targetFileId = null;
+    
+    if (window.isCompositeEdit) {
+        isEdit = true;
+        targetFileId = initialAddId;
+    } else if (loadedModels.length === 1 && String(loadedModels[0].userData.fileId) === String(initialAddId)) {
+        isEdit = true;
+        targetFileId = initialAddId;
+    }
     
     if (isEdit) {
-        const singleModel = loadedModels[0];
+        // Just checking if we want to warn
-        if (singleModel.userData.status === 'sliced') {
+        if (loadedModels.length === 1 && loadedModels[0].userData.status === 'sliced') {
             if (!confirm("{{ _('This model has already been sliced. The existing GCode will be overwritten. Continue?') }}")) {
                 return;
             }
+        } else if (window.isCompositeEdit) {
+            if (!confirm("{{ _('You are editing a composite model. The existing composite will be updated and re-sliced. Continue?') }}")) {
+                return;
+            }
         }
     }
     
@@ -613,7 +669,7 @@ function mergeAndSlice() {
         return {
             file_id: m.userData.fileId,
             matrix: mat.elements, // Array of 16 numbers used for slicing
-            raw_matrix: m.matrix.elements // Local visual properties
+            raw_matrix: m.matrixWorld.elements // Use world matrix explicitly just in case
         };
     });
     
@@ -636,7 +692,7 @@ function mergeAndSlice() {
         headers: {
             'Content-Type': 'application/json'
         },
-        body: JSON.stringify({ pieces: pieces, quality: quality, infill: infill, support: support, support_pattern: supportPattern, is_edit: isEdit })
+        body: JSON.stringify({ pieces: pieces, quality: quality, infill: infill, support: support, support_pattern: supportPattern, is_edit: isEdit, target_file_id: targetFileId })
     })
     .then(response => response.json())
     .then(data => {
@@ -671,6 +727,10 @@ document.addEventListener('DOMContentLoaded', () => {
     if (addId) {
         const btn = document.getElementById('add-model-btn-' + addId);
         if (btn) {
+            let matrixData = btn.getAttribute('data-matrix');
+            if (matrixData && matrixData.includes('"is_composite"')) {
+                window.isCompositeEdit = true;
+            }
             btn.click();
         }
     }

assets/i18n/en.json

@@ -44,6 +44,10 @@
     "No files uploaded yet.": "No files uploaded yet.",
     "Drag & Drop STL file here or Click to Select": "Drag & Drop STL file here or Click to Select",
     "Uploading...": "Uploading...",
+    "Simplifying": "Simplifying",
+    "Simplifying...": "Simplifying...",
+    "Proxy Skip Size (MB)": "Proxy Skip Size (MB)",
+    "Files smaller than this will not generate a simplified proxy.": "Files smaller than this will not generate a simplified proxy.",
     "Slicing queued!": "Slicing queued!",
     "Draft Quality": "Draft Quality",
     "Standard Quality": "Standard Quality",

assets/i18n/zh-cn.json

@@ -40,6 +40,10 @@
     "No files uploaded yet.": "还没有上传文件。",
     "Drag & Drop STL file here or Click to Select": "将 STL 文件拖放到此处或点击选择",
     "Uploading...": "上传中...",
+    "Simplifying": "简化中",
+    "Simplifying...": "正在简化...",
+    "Proxy Skip Size (MB)": "代理免简化大小 (MB)",
+    "Files smaller than this will not generate a simplified proxy.": "极小体积的文件无需降维生成加速展现的代理文件。",
     "Upload Complete!": "上传完成!",
     "Upload error.": "上传出错。",
     "Upload failed.": "上传失败。",

stl_merger.py

@@ -2,89 +2,52 @@ import struct
 import math
 import os
 
-def transform_stl(input_path, output_path, matrix):
-    # matrix is a flat 16 float array from Three.js (column-major format)
-    # [m0, m1, m2, m3,  m4, m5, m6, m7,  m8, m9, m10, m11,  m12, m13, m14, m15]
-    
-    with open(input_path, 'rb') as f:
-        header = f.read(80)
-        num_faces = struct.unpack('<I', f.read(4))[0]
-        
-        faces = f.read()
-
-    # Precompute for speed
-    def apply_m(_x, _y, _z):
-        w = _x * matrix[3] + _y * matrix[7] + _z * matrix[11] + matrix[15]
-        nx = (_x * matrix[0] + _y * matrix[4] + _z * matrix[8] + matrix[12]) / w
-        ny = (_x * matrix[1] + _y * matrix[5] + _z * matrix[9] + matrix[13]) / w
-        nz = (_x * matrix[2] + _y * matrix[6] + _z * matrix[10] + matrix[14]) / w
-        return nx, ny, nz
-
-    def apply_rot(_nx, _ny, _nz):
-        # Normals don't need translation, only upper 3x3
-        # Assuming isotropic scaling for normals, otherwise needs inverse transpose
-        x = _nx * matrix[0] + _ny * matrix[4] + _nz * matrix[8]
-        y = _nx * matrix[1] + _ny * matrix[5] + _nz * matrix[9]
-        z = _nx * matrix[2] + _ny * matrix[6] + _nz * matrix[10]
-        length = math.sqrt(x*x + y*y + z*z)
-        if length > 0.000001:
-            return x/length, y/length, z/length
-        return 0.0, 0.0, 0.0
-
-    out = bytearray(80 + 4 + num_faces * 50)
-    out[0:80] = header
-    out[80:84] = struct.pack('<I', num_faces)
-    
-    offset = 84
-    src_offset = 0
-    for _ in range(num_faces):
-        face_data = faces[src_offset:src_offset+50]
-        if len(face_data) < 50:
-            break
-            
-        nx, ny, nz, v1x, v1y, v1z, v2x, v2y, v2z, v3x, v3y, v3z, attr = struct.unpack('<12fH', face_data)
-        
-        # Transform normal
-        nnx, nny, nnz = apply_rot(nx, ny, nz)
-        # Transform vertices
-        nv1x, nv1y, nv1z = apply_m(v1x, v1y, v1z)
-        nv2x, nv2y, nv2z = apply_m(v2x, v2y, v2z)
-        nv3x, nv3y, nv3z = apply_m(v3x, v3y, v3z)
-        
-        struct.pack_into('<12fH', out, offset, nnx, nny, nnz, nv1x, nv1y, nv1z, nv2x, nv2y, nv2z, nv3x, nv3y, nv3z, attr)
-        offset += 50
-        src_offset += 50
-        
-    with open(output_path, 'wb') as f:
-        f.write(out)
-
-    return num_faces
-
 def merge_stls(input_files, output_path):
     try:
-        import trimesh
+        from stl import mesh
         import numpy as np
         
         meshes = []
         for path, matrix in input_files:
-            mesh = trimesh.load(path, file_type='stl')
+            try:
-            m = np.array(matrix, dtype=np.float64).reshape((4, 4)).T
+                # 重新换回轻量级的 numpy-stl 以防内存溢出 (OOM)
-            mesh.apply_transform(m)
+                m = mesh.Mesh.from_file(path)
-            meshes.append(mesh)
+                
-            
+                mat = np.array(matrix, dtype=np.float64).reshape((4, 4)).T
+                
+                vectors = m.vectors.reshape(-1, 3)
+                hom_vectors = np.hstack((vectors, np.ones((len(vectors), 1), dtype=np.float32)))
+                transformed = (mat @ hom_vectors.T).T
+                m.vectors = transformed[:, :3].reshape(-1, 3, 3)
+                
+                # 检测缩放矩阵是否引发镜像翻转 (行列式为负数)
+                det = np.linalg.det(mat[:3, :3])
+                if det < 0:
+                    # 发生镜像反转，不仅法线会反向，三角形三个顶点的顺逆时针（Winding Order）也会错乱
+                    # 强行交换每个三角形的顶点2和顶点3以纠正渲染正反面
+                    m.vectors[:, [1, 2]] = m.vectors[:, [2, 1]]
+                
+                m.update_normals()
+                meshes.append(m)
+            except Exception as e:
+                print(f"Error processing path {path} with stl mesh: {e}")
+                
         if not meshes:
             return
-        elif len(meshes) == 1:
-            merged = meshes[0]
-        else:
-            merged = trimesh.util.concatenate(meshes)
             
-        merged.export(output_path, file_type='stl')
+        if len(meshes) == 1:
+            meshes[0].save(output_path)
+            return
+            
+        merged_data = np.concatenate([m.data for m in meshes])
+        merged_mesh = mesh.Mesh(merged_data)
+        merged_mesh.save(output_path)
         return
+        
     except Exception as e:
-        print(f"Trimesh fast-merge failed: {e}, falling back to struct parsing.")
+        print(f"Mesh fast-merge failed: {e}. Falling back to struct parsing.")
-        pass # Fallback to slower python struct method
 
+    # Extreme fallback just in case no stl libraries work
     total_faces = 0
     meshes_data = []
 
@@ -94,25 +57,12 @@ def merge_stls(input_files, output_path):
             faces = struct.unpack('<I', f.read(4))[0]
             data = f.read(faces * 50)
             
-            # transform data
-            # To speed things up, we could just do the transform in python like above
-            # For this simple prototype, let's process each file into memory:
-            
             def apply_m(_x, _y, _z):
                 w = _x * matrix[3] + _y * matrix[7] + _z * matrix[11] + matrix[15]
                 nx = (_x * matrix[0] + _y * matrix[4] + _z * matrix[8] + matrix[12]) / w
                 ny = (_x * matrix[1] + _y * matrix[5] + _z * matrix[9] + matrix[13]) / w
                 nz = (_x * matrix[2] + _y * matrix[6] + _z * matrix[10] + matrix[14]) / w
                 return nx, ny, nz
-
-            def apply_rot(_nx, _ny, _nz):
-                x = _nx * matrix[0] + _ny * matrix[4] + _nz * matrix[8]
-                y = _nx * matrix[1] + _ny * matrix[5] + _nz * matrix[9]
-                z = _nx * matrix[2] + _ny * matrix[6] + _nz * matrix[10]
-                length = math.sqrt(x*x + y*y + z*z)
-                if length > 0.000001:
-                    return x/length, y/length, z/length
-                return 0.0, 0.0, 0.0
             
             new_data = bytearray(faces * 50)
             src_offset = 0
@@ -120,11 +70,28 @@ def merge_stls(input_files, output_path):
             for _ in range(faces):
                 n_x, n_y, n_z, v1x, v1y, v1z, v2x, v2y, v2z, v3x, v3y, v3z, attr = struct.unpack_from('<12fH', data, src_offset)
                 
-                nnx, nny, nnz = apply_rot(n_x, n_y, n_z)
                 nv1x, nv1y, nv1z = apply_m(v1x, v1y, v1z)
                 nv2x, nv2y, nv2z = apply_m(v2x, v2y, v2z)
                 nv3x, nv3y, nv3z = apply_m(v3x, v3y, v3z)
                 
+                # Recalculate normal properly using cross product to fix flipped/sheared surfaces
+                Ux = nv2x - nv1x
+                Uy = nv2y - nv1y
+                Uz = nv2z - nv1z
+                Vx = nv3x - nv1x
+                Vy = nv3y - nv1y
+                Vz = nv3z - nv1z
+                
+                nnx = Uy * Vz - Uz * Vy
+                nny = Uz * Vx - Ux * Vz
+                nnz = Ux * Vy - Uy * Vx
+                
+                l = math.sqrt(nnx**2 + nny**2 + nnz**2)
+                if l > 1e-8:
+                    nnx, nny, nnz = nnx/l, nny/l, nnz/l
+                else:
+                    nnx, nny, nnz = 0.0, 0.0, 0.0
+                
                 struct.pack_into('<12fH', new_data, dst_offset, nnx, nny, nnz, nv1x, nv1y, nv1z, nv2x, nv2y, nv2z, nv3x, nv3y, nv3z, attr)
                 src_offset += 50
                 dst_offset += 50
@@ -132,7 +99,6 @@ def merge_stls(input_files, output_path):
             meshes_data.append(new_data)
             total_faces += faces
             
-    # write merged
     with open(output_path, 'wb') as f:
         f.write(b'\0' * 80)
         f.write(struct.pack('<I', total_faces))