Match demo.zip render settings: enable GPU rendering with 512 samples

- Changed samples from 64 to 512 for higher quality (matching demo.zip)
- Changed device from forced CPU to GPU-first with CPU fallback
- Added comprehensive GPU detection logic (NVIDIA/Apple/AMD)
- Implements automatic CPU fallback if GPU unavailable
- Fully complies with demo.zip rendering specifications

code/cube3d/render/render_bricks_safe.py

@@ -346,8 +346,8 @@ try:
             scene.camera = bpy.context.active_object
 
     scene.render.engine = 'CYCLES'
-    scene.cycles.samples = 64  # 降低采样数加快 CPU 渲染
-    scene.cycles.device = 'CPU'  # 强制 CPU 渲染（云平台更稳定）
+    scene.cycles.samples = 512  # 与 demo.zip 一致的高质量渲染
+    scene.cycles.device = 'GPU'
     scene.render.image_settings.file_format = 'PNG'
     scene.render.filepath = "{output_file}"
     scene.render.use_overwrite = True
@@ -356,10 +356,34 @@ try:
     bpy.context.view_layer.cycles.use_denoising = False
     print("ℹ️  Denoising disabled (apt-get Blender has no OpenImageDenoise support)")
 
-    print("ℹ️  使用 CPU 渲染（samples=64，云平台优化配置）")
+    # GPU 配置（与 demo.zip 一致）- 优先使用 GPU，失败则自动回退到 CPU
+    if sys.platform == 'darwin':
+        compute_device_type = 'METAL'
+    else:
+        compute_device_type = 'CUDA'
 
-    # GPU 配置已禁用（HuggingFace Spaces 不支持图形 GPU）
-    # 如需 GPU 渲染，请部署到支持 CUDA 图形能力的平台
+    print("🔧 配置 GPU...")
+    try:
+        bpy.context.preferences.addons['cycles'].preferences.compute_device_type = compute_device_type
+        bpy.context.preferences.addons['cycles'].preferences.get_devices()
+        gpu_used = False
+        for device in bpy.context.preferences.addons['cycles'].preferences.devices:
+            if device['name'].startswith(('NVIDIA', 'Apple', 'AMD')):
+                device['use'] = 1
+                gpu_used = True
+                print(f"✅ 启用 GPU: {{device['name']}}")
+            else:
+                device['use'] = 0
+        if not gpu_used:
+            print("⚠️  未找到可用 GPU，将回退到 CPU 渲染")
+            scene.cycles.device = 'CPU'
+            print("ℹ️  使用 CPU 渲染（samples=512）")
+        else:
+            print(f"ℹ️  使用 GPU 渲染（{compute_device_type}, samples=512）")
+    except Exception as gpu_error:
+        print(f"⚠️  GPU 初始化失败: {{gpu_error}}")
+        print("ℹ️  回退到 CPU 渲染（samples=512）")
+        scene.cycles.device = 'CPU'
 
     print("开始渲染...")
     result = bpy.ops.render.render(write_still=True)