add occ blogs

_posts/2023-05-24-OCCT-sample-projects.md

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+---
+title: OCCT projects on github
+date: 2023-05-24 +0800 # 2022-01-01 13:14:15 +0800 只写日期也行；不写秒也行；这样也行 2022-03-09T00:55:42+08:00
+categories: [OCCT]
+tags: [occt]      # TAG names should always be lowercase
+
+# 以下默认false
+math: true
+mermaid: true
+# pin: true
+---
+
+# OCCT projects on github
+
+## OCCT samples
+
+需要安装 `OpenGL`： [基于Ubuntu搭建OpenGL开发环境](https://www.cnblogs.com/jiujiubashiyi/p/16429717.html)
+
+```bash
+sudo apt-get install libglfw3-dev
+sudo apt install mesa-utils
+```
+
+以下两个项目均来自 [github gkv311](https://github.com/gkv311)
+
+* [occt-samples-qopenglwidget](https://gitee.com/occt/occt-samples-qopenglwidget.git)
+* [occt-hello](https://gitee.com/occt/occt-hello)
+
+## OCCT 文章
+
+### Boolean
+
+* [Open Cascade中的布尔操作](http://cppblog.com/eryar/archive/2013/01/17/197357.html)
+* [OpenCASCADE 布尔运算简介](https://www.cnblogs.com/opencascade/p/OCCT_BO_Intro.html)
+* [OpenCasCade拓扑几何的布尔运算](https://blog.csdn.net/qq_22642239/article/details/97271457)
+* [Boolean Operations](https://dev.opencascade.org/doc/overview/html/occt_user_guides__modeling_algos.html#occt_modalg_5)
+* [OpenCascade Modeling Algorithms Boolean Operations](https://www.cnblogs.com/opencascade/p/3511140.html)
+
+### Fillet
+
+* [autoCAD doc Fillet](https://help.autodesk.com/view/ACD/2023/ENU/?guid=GUID-64F8B700-23B3-4BD6-8C03-66121AA13E8F)
+
+### Mesh
+
+* [Mesh](https://dev.opencascade.org/doc/overview/html/occt_user_guides__mesh.html)

_posts/2023-05-24-Ubuntu install OCCT.md

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+---
+title: Ubuntu 安装 OCCT
+date: 2023-05-24 +0800 # 2022-01-01 13:14:15 +0800 只写日期也行；不写秒也行；这样也行 2022-03-09T00:55:42+08:00
+categories: [OCCT]
+tags: [occt]      # TAG names should always be lowercase
+
+# 以下默认false
+math: true
+mermaid: true
+# pin: true
+---
+
+## OCCT 依赖库
+
+* [Introduction -- Requirements](https://dev.opencascade.org/doc/overview/html/index.html)
+
+## 下载OpenCascade
+
+`OCC 7.7`编译有问题，使能`VTK`时编译错误，下载最新版的`OCC`修复该问题：
+
+```bash
+# https://dev.opencascade.org/resources/git_repository
+git clone https://git.dev.opencascade.org/repos/occt.git occt
+```
+
+## 编译安装命令
+
+### 1. 编译安装第三方库
+
+* 注意要 `tcl-dev`, `tk-dev`, `tcllib`, `tklib`，除非自己编译安装，此时要设置TCL/TK相关的路径，比较麻烦。
+
+```bash
+sudo apt-get install tcllib tklib tcl-dev tk-dev libfreetype-dev libx11-dev libgl1-mesa-dev libfreeimage-dev
+sudo apt-get install rapidjson-dev libdraco-dev
+```
+
+`tcl 8.6`编译安装命令(`tk 8.6`相同的编译配置命令)：
+
+```bash
+# https://www.tcl.tk/software/tcltk/8.6.html
+
+cd tcl8.6.13/unix
+./configure --enable-gcc  --enable-shared --enable-threads --enable-64bit
+make && sudo make install
+```
+
+`freeType`编译安装命令：
+
+```bash
+# https://freetype.org/download.html
+
+CFLAGS='-m64 -fPIC' CPPFLAGS='-m64 -fPIC' ./configure
+make && sudo make install
+```
+
+`FreeImage`编译安装命令：
+
+```bash
+# https://freeimage.sourceforge.io/download.html
+# 修改 Makefile.fip：增加 CXXFLAGS += -std=c++11
+make -f Makefile.fip
+# 拷贝头文件及 .so, .a 到相应目录
+```
+
+编译安装`fdk-acc`及`ffmpeg`:
+
+```bash
+# install dependencies
+sudo apt install libavformat-dev libavcodec-dev libswresample-dev libswscale-dev libavutil-dev libsdl1.2-dev libx264-dev nasm
+
+# tdk-acc
+./configure && make && sudo make install
+
+# ffmpeg
+./configure --enable-gpl --enable-nonfree --enable-libfdk-aac --enable-libx264 --enable-filter=delogo --enable-shared --enable-pthreads
+make && sudo make install
+```
+
+### 2. 编译安装 OCCT
+
+```bash
+cd opencascade-7.7.0
+mdkir build && cd build
+
+# 配置OCC编译，使能VTK, ITK等功能
+ccmake ..
+
+make -j6
+sudo make install
+```
+
+几次配置截图之后，配置如下
+
+![ccmake1](/assets/images/occ/ccmake01.png)
+
+![ccmake2](/assets/images/occ/ccmake02.png)
+
+### 3. 安装或编译 Qt5
+
+* 安装 Qt5
+
+```bash
+sudo apt-get install qtbase5-dev qtchooser qt5-qmake qtbase5-dev-tools
+sudo apt-get install qtcreator
+```
+
+* 编译 Qt5
+
+编译及设置环境变量见 [VTK（1）：ubuntu 22.04 源码编译安装 Qt5.15.6](https://www.cnblogs.com/vaughnhuang/articles/16678048.html)
+
+## 国内学习博客
+
+* [OpenCascade基本框架介绍-昨夜星辰 (hustlei.github.io)](https://hustlei.github.io/2014/10/opencascade-introduction-and-compile.html)
+* [OpenCASCADE入门指南 - opencascade - 博客园 (cnblogs.com)](https://www.cnblogs.com/opencascade/p/OpenCASCADE_StartGuide.html)
+* [2.OpenCASCADE - eryar - C++博客 (cppblog.com)](http://cppblog.com/eryar/category/17808.html?Show=All)
+
+## 引用资料
+
+* [Build 3rd-parties - Open CASCADE Technology Documentation](https://dev.opencascade.org/doc/overview/html/build_upgrade_building_3rdparty.html#build_3rdparty_linux)
+* [Build OCCT - Open CASCADE Technology Documentation](https://dev.opencascade.org/doc/occt-7.6.0/overview/html/build_upgrade__building_occt.html#build_occt_win_cmake)
+* [Download - Open CASCADE Technology](https://dev.opencascade.org/release)
+* [3rd party Components](https://dev.opencascade.org/resources/download/3rd-party-components)
+* [TCL/TK 8.6](https://www.tcl.tk/software/tcltk/download.html)

_posts/2023-05-25-OCCT-build-with-samples.md

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+---
+title: Ubuntu 编译 Qt + VTK + OCCT + samples
+date: 2023-05-25 +0800 # 2022-01-01 13:14:15 +0800 只写日期也行；不写秒也行；这样也行 2022-03-09T00:55:42+08:00
+categories: [OCCT]
+tags: [occt]      # TAG names should always be lowercase
+
+# 以下默认false
+math: true
+mermaid: true
+# pin: true
+---
+
+# Ubuntu 编译 Qt + VTK + OCCT + samples
+
+## 1. 卸载安装的Qt，编译安装Qt
+
+实践发现使用安装的`Qt`，编译带`samples`的`OCCT`在`CMake`阶段就出错（可能是Ubuntu系统中环境有问题，或者是没有完整设置`Qt`相关变量）。
+
+使用手动编译安装的`Qt`，并设置好相关环境变量可正常编译带`samples`的`OCCT`。手动编译安装`Qt`见：[VTK（1）：ubuntu 22.04 源码编译安装 Qt5.15.6](https://www.cnblogs.com/vaughnhuang/articles/16678048.html) 。
+
+## 2. 编译 VTK
+
+[VTK （2）：ubuntu 22.04 编译 VTK 9.2 rc2](https://www.cnblogs.com/vaughnhuang/articles/16683118.html)
+
+## 2. 编译 OCCT 及 samples
+
+顶层`CMakeLists.txt`中有变量`BUILD_SAMPLES_QT`控制是否编译`samples`（包括qt相关samples）。
+
+```bash
+cmake -D3RDPARTY_QT_DIR=/usr/local/Qt-5.15.6 -DCMAKE_BUILD_TYPE=Debug -DBUILD_SAMPLES_QT=ON ..
+make -j
+```

_posts/2023-06-12-OCCT-bounding-box.md

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+---
+title: OCC boundding box 以及 distance
+date: 2023-06-12 +0800 # 2022-01-01 13:14:15 +0800 只写日期也行；不写秒也行；这样也行 2022-03-09T00:55:42+08:00
+categories: [OCCT]
+tags: [occt]      # TAG names should always be lowercase
+
+# 以下默认false
+math: true
+mermaid: true
+# pin: true
+---
+
+# OCC boundding box 以及 distance
+
+## bounding box 方式检测
+
+```C++
+#include <Bnd_Box.hxx>
+#include <BRepBndLib.hxx>
+
+TopoDS_Shape shape1, shape2; // Assume these shapes are already defined
+Bnd_Box boundingBox1, boundingBox2;
+
+BRepBndLib::Add(shape1, boundingBox1);
+BRepBndLib::Add(shape2, boundingBox2);
+
+bool isInterfering = !boundingBox1.IsOut(boundingBox2);
+```
+
+## distance 方式检测
+
+```C++
+#include <BRepExtrema_DistShapeShape.hxx>
+
+BRepExtrema_DistShapeShape distShapeShape(shape1, shape2);
+Standard_Real minDistance = distShapeShape.Value();
+bool isInterfering = (minDistance <= Precision::Confusion());
+```
+
+* BRepExtrema_DistShapeShape 比 bounding box 方式费时；
+* 如果`bouding box`方式检测出来出现干涉（interference, overlap），则可以使用`distance`检测方式确认；

_posts/2023-06-12-OCCT-explore-api-usage.md

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+---
+title: OCC TopExp_Explorer 用法
+date: 2023-06-12 +0800 # 2022-01-01 13:14:15 +0800 只写日期也行；不写秒也行；这样也行 2022-03-09T00:55:42+08:00
+categories: [OCCT]
+tags: [occt]      # TAG names should always be lowercase
+
+# 以下默认false
+math: true
+mermaid: true
+# pin: true
+---
+
+# OCC TopExp_Explorer 用法
+
+```c++
+#include <iostream>
+#include <TopoDS_Shape.hxx>
+#include <TopExp_Explorer.hxx>
+
+using namespace std;
+
+int main()
+{
+  // Create a TopoDS_Shape object.
+  TopoDS_Shape shape;
+
+  // Create a TopExp_Explorer object and explore the shape.
+  TopExp_Explorer exp(shape, TopAbs_FACE);
+
+  // While there are more faces, print the face's name.
+  while (exp.More())
+  {
+    cout << exp.Current().Name() << endl;
+    exp.Next();
+  }
+
+  return 0;
+}
+```

_posts/2023-06-14-OCCT-BHV-tree-bounding-box.md

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+---
+title: OCCT 使用 BVH 树加速 bounding box 查找遍历
+date: 2023-06-14 +0800 # 2022-01-01 13:14:15 +0800 只写日期也行；不写秒也行；这样也行 2022-03-09T00:55:42+08:00
+categories: [OCCT]
+tags: [occt]      # TAG names should always be lowercase
+
+# 以下默认false
+math: true
+mermaid: true
+# pin: true
+---
+
+# OCCT 使用 BVH 树加速 bounding box 查找遍历
+
+## Demo code
+
+### Demo code 1
+
+```C++
+#include <BVH_Tree.hxx>
+#include <TopoDS_Shape.hxx>
+#include <vector>
+
+// Assuming you have a vector of TopoDS_Shape objects called 'shapes'
+
+// Create a BVH tree
+Handle(BVH_Tree<Standard_Real, 3>) bvhTree = new BVH_Tree<Standard_Real, 3>();
+
+// Insert the shapes into the BVH tree
+for (const auto& shape : shapes) {
+  // Compute the bounding box for the shape
+  Bnd_Box box;
+  BRepBndLib::Add(shape, box);
+
+  // Insert the bounding box into the BVH tree
+  bvhTree->Insert(box, shape);
+}
+
+// a query on the BVH tree to find possible interference
+bvhTree->Select([](const TopoDS_Shape& shape1, const TopoDS_Shape& shape2) {
+  // Check for interference between shape1 and shape2
+  // If there is interference, process it accordingly
+});
+
+```
+
+### Demo code 2
+
+```C++
+#include <SpatialHash.hxx>
+#include <TopoDS_Shape.hxx>
+
+int main()
+{
+  // Create a spatial hash from the shapes.
+  SpatialHash hash(shapes.size());
+  for (TopoDS_Shape& shape : shapes)
+  {
+    hash.Add(shape);
+  }
+
+  // Find possibly interfering objects.
+  for (TopoDS_Shape& shape : shapes)
+  {
+    std::vector<TopoDS_Shape> interferingObjects = hash.Find(shape);
+    for (TopoDS_Shape& otherShape : interferingObjects)
+    {
+      // Check if the shapes interfere.
+    }
+  }
+
+  return 0;
+}
+```
+
+## References
+
+* [几何体数据结构学习（6）BVH树](https://zhuanlan.zhihu.com/p/430469154)