PythonOCC 3D圖形庫學習—創建立方體模型

Open CASCADE（簡稱OCC）平臺是是一個開源的C++類庫，OCC主要用于開發二維和三維幾何建模應用程序，包括通用的或專業的計算機輔助設計CAD系統、制造或分析領域的應用程序、仿真應用程序或圖形演示工具。

PythonOCC是對Open CASCADE的封裝。PythonOCC按照官方描述：3D CAD/CAE/PLM DEVELOPMENT FRAMEWORK FOR THE PYTHON PROGRAMMING LANGUAGE. 即用于開發CAD/CAE/CAM程序的一個Python框架。PythonOCC的下載地址為：http://www.pythonocc.org/download/

學習一個框架先從最簡單的"Hello world"程序開始，下面用PythonOCC創建一個最簡單的立方體并顯示出來。

'''
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()

顯示結果如下，按鍵盤上的W，S，H鍵可以在線框模型，面模型和消隱線模型之間切換。按住左鍵移動鼠標可以旋轉物體，鼠標中鍵用于縮放，按住鼠標中鍵可以平移物體

參考：

http://www.pythonocc.org/

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

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