PythonOCC 3D图形库学习—创建立方体模型

Open CASCADE（简称OCC）平台是是一个开源的C++类库，OCC主要用于开发二维和三维几何建模应用程序，包括通用的或专业的计算机辅助设计CAD系统、制造或分析领域的应用程序、仿真应用程序或图形演示工具。

PythonOCC是对Open CASCADE的封装。PythonOCC按照官方描述：3D CAD/CAE/PLM DEVELOPMENT FRAMEWORK FOR THE PYTHON PROGRAMMING LANGUAGE. 即用于开发CAD/CAE/CAM程序的一个Python框架。PythonOCC的下载地址为：http://www.pythonocc.org/download/

学习一个框架先从最简单的"Hello world"程序开始，下面用PythonOCC创建一个最简单的立方体并显示出来。

 '''
 This examples creates and displays a simple box.
 '''

 # The first line loads the init_display function, necessary to
 # enable the builtin simple gui provided with pythonocc
 from OCC.Display.SimpleGui import init_display

 # Then we import the class that instanciates a box
 # Here the BRepPrimAPI module means Boundary Representation Primitive API.
 # It provides an API for creation of basic geometries like spheres,cones etc
 from OCC.BRepPrimAPI import BRepPrimAPI_MakeBox

 # Following line initializes the display
 # By default, the init_display function looks for a Qt based Gui (PyQt, PySide)
 display, start_display, add_menu, add_function_to_menu = init_display()

 # The BRepPrimAPI_MakeBox class is initialized with the 3 parameters of the box: widht, height, depth
 my_box = BRepPrimAPI_MakeBox(10., 20., 30.).Shape()

 # Then the box shape is sent to the renderer
 display.DisplayShape(my_box, update=True)

 # At last, we enter the gui mainloop
 start_display()

显示结果如下，按键盘上的W，S，H键可以在线框模型，面模型和消隐线模型之间切换。按住左键移动鼠标可以旋转物体，鼠标中键用于缩放，按住鼠标中键可以平移物体

参考：

http://www.pythonocc.org/

http://www.vrplumber.com/py3d.py

https://github.com/tpaviot/pythonocc-core/blob/5b7ac9167e50e302cea534c5c7777ca2432f6d09/doc/examples/helloworld.rst