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C# から Open CASCAD Technology (C++) を参照する【座標抽出編】

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はじめに

C# から Open CASCAD Technology (C++) を参照する備忘録です。続きです。

改訂履歴

  • 2026/07/22 : 初版公開。

本文

1. 環境

  • .NET Framework 4.8.1
  • Open CASCADE Technology 8.0.0
  • Visual Studio Community 2022

2. 手順

2-1. C++ プログラムの作成

トポロジー形状データを保持する C++ クラスを作ります（厳密には異なるようです）。

NativeOcctShape.h
#pragma once

#include <TopoDS_Shape.hxx>
#include <vector>

struct NativePoint3D
{
    double X;
    double Y;
    double Z;
};

class NativeOcctShape
{
public:
    explicit NativeOcctShape(const TopoDS_Shape& shape);
    TopoDS_Shape GetShape() const;
    std::vector<NativePoint3D> GetVertices() const;

private:
    TopoDS_Shape m_shape;
};
NativeOcctShape.cpp
#include "NativeOcctShape.h"

#include <TopExp_Explorer.hxx>
#include <TopoDS.hxx>
#include <TopoDS_Vertex.hxx>
#include <BRep_Tool.hxx>
#include <gp_Pnt.hxx>

NativeOcctShape::NativeOcctShape(const TopoDS_Shape& shape)
    : m_shape(shape)
{
}

TopoDS_Shape NativeOcctShape::GetShape() const
{
    return m_shape;
}

std::vector<NativePoint3D> NativeOcctShape::GetVertices() const
{
    std::vector<NativePoint3D> result;

    for (TopExp_Explorer exp(m_shape, TopAbs_VERTEX); exp.More(); exp.Next())
    {
        TopoDS_Vertex vertex = TopoDS::Vertex(exp.Current());
        gp_Pnt p = BRep_Tool::Pnt(vertex);
        result.push_back({ p.X(), p.Y(), p.Z() });
    }

    return result;
}

次に STEP ファイルの読込クラスを作成します。

NativeStepReader.h
#pragma once

#include "NativeOcctShape.h"

class NativeStepReader
{
public:
    static NativeOcctShape* Load(const char* path);
};
NativeStepReader.cpp
#pragma once

#include "NativeStepReader.h"
#include "NativeOcctShape.h"

#include <IFSelect_ReturnStatus.hxx>
#include <STEPControl_Reader.hxx>
#include <TopoDS_Shape.hxx>

NativeOcctShape* NativeStepReader::Load(const char* path)
{
    // 読込する。
    STEPControl_Reader reader;
    IFSelect_ReturnStatus status = reader.ReadFile(path);
    if (status != IFSelect_RetDone)
    {
        return nullptr;
    }

    // 読込したデータを形状クラスに変換する。
    reader.TransferRoots();
    TopoDS_Shape readShape = reader.OneShape();
    if (readShape.IsNull())
    {
        return nullptr;
    }

    // 結果を返す。
    NativeOcctShape* result = new NativeOcctShape(readShape);
    return result;
}

作成した NativeOcctShape.cpp・NativeStepReader.cpp のプロパティを開き、Debug / Release 構成共に共通言語ランタイムサポートは使用しないように設定します。

2-2. C++/CLI プログラムの作成

C++/CLI 側を作っていきます。トポロジー形状データを保持するクラスを作ります。

OcctShape.h
#pragma once

class NativeOcctShape;

namespace OcctLibrary
{
    public value struct Point3D
    {
    public:
        double X;
        double Y;
        double Z;
    };

    public ref class OcctShape
    {
    public:
        OcctShape();
        ~OcctShape();
        !OcctShape();
        array<Point3D>^ GetVertices();

    internal:
        OcctShape(NativeOcctShape* nativePtr);
        NativeOcctShape* GetNativeInstance();

    private:
        NativeOcctShape* m_NativeInstance;
    };
}
OcctShape.cpp
#include "OcctShape.h"
#include "NativeOcctShape.h"

namespace OcctLibrary
{
    OcctShape::OcctShape()
    {
        m_NativeInstance = nullptr;
    }

    OcctShape::OcctShape(NativeOcctShape* nativePtr)
    {
        m_NativeInstance = nativePtr;
    }

    OcctShape::~OcctShape()
    {
        this->!OcctShape();
    }

    OcctShape::!OcctShape()
    {
        if (m_NativeInstance != nullptr)
        {
            delete m_NativeInstance;
            m_NativeInstance = nullptr;
        }
    }

    array<Point3D>^ OcctShape::GetVertices()
    {
        if (m_NativeInstance == nullptr)
        {
            return nullptr;
        }

        std::vector<NativePoint3D> nativeVertices = m_NativeInstance->GetVertices();
        array<Point3D>^ result = gcnew array<Point3D>(static_cast<int>(nativeVertices.size()));

        for (int i = 0; i < static_cast<int>(nativeVertices.size()); i++)
        {
            result[i].X = nativeVertices[i].X;
            result[i].Y = nativeVertices[i].Y;
            result[i].Z = nativeVertices[i].Z;
        }

        return result;
    }

    NativeOcctShape* OcctShape::GetNativeInstance()
    {
        return m_NativeInstance;
    }
}

次に STEP ファイルの読込クラスを作成します。

StepReader.h
#pragma once

class NativeStepReader;

namespace OcctLibrary
{
    ref class OcctShape;

    public ref class StepReader
    {
    public:
        StepReader();
        ~StepReader();
        !StepReader();
        OcctShape^ Load(System::String^ path);

    private:
        NativeStepReader* m_nativeReader;
    };
}
StepReader.cpp
#include <windows.h>
#include "NativeStepReader.h"
#include "NativeOcctShape.h"
#include "OcctShape.h"
#include "StepReader.h"
#include <msclr/marshal_cppstd.h>

namespace OcctLibrary
{
    StepReader::StepReader()
    {
        m_nativeReader = new NativeStepReader();
    }

    StepReader::~StepReader()
    {
        this->!StepReader();
    }

    StepReader::!StepReader()
    {
        if (m_nativeReader != nullptr)
        {
            delete m_nativeReader;
            m_nativeReader = nullptr;
        }
    }

    OcctShape^ StepReader::Load(System::String^ path)
    {
        if (m_nativeReader == nullptr || System::String::IsNullOrEmpty(path))
        {
            return nullptr;
        }

        msclr::interop::marshal_context context;
        const char* nativePath = context.marshal_as<const char*>(path);

        NativeOcctShape* nativeShapePtr = m_nativeReader->Load(nativePath);
        if (nativeShapePtr == nullptr)
        {
            return nullptr;
        }

        return gcnew OcctShape(nativeShapePtr);
    }
}

作成した OcctShape.cpp・StepReader.cpp のプロパティを開き、Debug / Release 構成共に共通言語ランタイムサポートは使用するように設定します。

3. 動作確認

テスト用に Windows Forms で画面を作りました。

インポートボタンで以下の処理が走ります。

MainForm.cs
private void ImportButton_Click(object sender, EventArgs e)
{
    // STEP ファイルを読込する。
    using (var stepReader = new StepReader())
    using (var shape = stepReader.Load(InputTextBox.Text))
    {
        if (shape != null)
        {
            // 形状の頂点座標を取得する。
            Point3D[] vertices = shape.GetVertices();

            // 重複を除去して、座標を小さい順にソートする。
            var sorted = vertices
                .GroupBy(v => new { v.X, v.Y, v.Z })
                .Select(g => g.First())
                .OrderBy(v => v.X)
                .ThenBy(v => v.Y)
                .ThenBy(v => v.Z)
                .ToList();

            // ソートされた座標をリストボックスに表示する。
            ResultListBox.Items.Clear();
            for (var i = 0; i < sorted.Count; i++)
            {
                ResultListBox.Items.Add($"[{i}]: X={sorted[i].X}, Y={sorted[i].Y}, Z={sorted[i].Z}");
            }
        }
    }
}

とりあえず、座標データが抽出されました。

以前 Occt.NET を検証した時と同じファイルです。ざっと見た感じ、合ってそうでした。

Result.log
[0]: X=-55, Y=-19.99999999999, Z=-100
[1]: X=-55, Y=-19.99999999999, Z=0
[2]: X=-55, Y=20, Z=-100
[3]: X=-55, Y=20, Z=0
[4]: X=-45, Y=-10, Z=-15
[5]: X=-45, Y=-10, Z=0
[6]: X=-45, Y=10, Z=-15
[7]: X=-45, Y=10, Z=0
[8]: X=-40, Y=-19.99999999999, Z=-10
[9]: X=-40, Y=-19.99999999999, Z=0
[10]: X=-40, Y=-10, Z=-10
[11]: X=-40, Y=-10, Z=0
[12]: X=-24, Y=-19.99999999999, Z=-10
[13]: X=-24, Y=-19.99999999999, Z=0
[14]: X=-24, Y=-10, Z=-10
[15]: X=-24, Y=-10, Z=0
[16]: X=-8, Y=-19.99999999999, Z=-10
[17]: X=-8, Y=-19.99999999999, Z=0
[18]: X=-8, Y=-10, Z=-10
[19]: X=-8, Y=-10, Z=0
[20]: X=8, Y=-19.99999999999, Z=-10
[21]: X=8, Y=-19.99999999999, Z=0
[22]: X=8, Y=-10, Z=-10
[23]: X=8, Y=-10, Z=0
[24]: X=20.358962517357, Y=20, Z=-100
[25]: X=20.358962517357, Y=20, Z=0
[26]: X=24, Y=-19.99999999999, Z=-10
[27]: X=24, Y=-19.99999999999, Z=0
[28]: X=24, Y=-10, Z=-10
[29]: X=24, Y=-10, Z=0
[30]: X=30.505081240903, Y=10, Z=-15
[31]: X=30.505081240903, Y=10, Z=0
[32]: X=40, Y=-19.99999999999, Z=-10
[33]: X=40, Y=-19.99999999999, Z=0
[34]: X=40, Y=-10, Z=-10
[35]: X=40, Y=-10, Z=0
[36]: X=55, Y=-19.99999999999, Z=-100
[37]: X=55, Y=-19.99999999999, Z=0
[38]: X=55, Y=-10, Z=-15
[39]: X=55, Y=-10, Z=0
[40]: X=79.999978668735, Y=15, Z=-50
[41]: X=79.999978668735, Y=15, Z=0

おわりに

残念ながら現状 UTF-8 / Unicode に対応していないため、ファイルパスに日本語があると動きません。適宜ソースを修正してください。

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