直线生产算法，理解基本图形元素光栅化的基本原理，掌握一种基本图形元素光栅化算法，利用OpenGL实现直线光栅化的DDA算法。-Straight-line production method, understanding the basic graphic elements of the basic principles of grating, have a basic graphic elements rasterization algorithms, the use of OpenGL to achieve straight-line grating of the DDA algorithm.