furniture-3d-system-Wu/autocad-plugin/FurnitureExporter/BrepSurfaceUtils.cs

using Autodesk.AutoCAD.Geometry;

namespace FurnitureExporter;

/// <summary>
/// Brep 面的 Surface 有时会被包装成 ExternalBoundedSurface/OffsetSurface 等“修剪/偏移”表面。
/// 这会导致直接用 `surface is Cylinder/Plane` 判断失效，从而漏检孔位/倒角等特征。
/// 
/// 这里提供一个统一的“剥壳”工具，把 Surface 还原为最底层的几何表面类型。
/// </summary>
internal static class BrepSurfaceUtils
{
    // 防御：最多剥 8 层，避免异常几何导致递归/循环
    private const int MaxUnwrapDepth = 8;

    public static Surface Unwrap(Surface surface)
    {
        var current = surface;

        for (int i = 0; i < MaxUnwrapDepth; i++)
        {
            if (current == null)
            {
                break;
            }

            // 最常见：Brep Face 的表面是“修剪面”，真正的几何在 BaseSurface
            if (current is ExternalBoundedSurface ebs && ebs.BaseSurface != null)
            {
                current = ebs.BaseSurface;
                continue;
            }

            // 偏移面：原始几何在 OriginalSurface
            if (current is OffsetSurface os && os.OriginalSurface != null)
            {
                current = os.OriginalSurface;
                continue;
            }

            // 外部面：如果是 NativeSurface，则真实几何在 nativeSurface
            if (current is ExternalSurface es && es.IsNativeSurface && es.nativeSurface != null)
            {
                current = es.nativeSurface;
                continue;
            }

            break;
        }

        return current ?? surface;
    }
}