橡皮筋技术带右键菜单功能，实现直线和矩形的橡皮筋技术，并采用右键菜单功能选择-Right-click menu functions with a rubber band technology, to achieve a straight line and rectangle rubber band technology, and feature selection using right-click menu

1.学习掌握橡皮筋绘制技术 2.熟悉opengl编程流程 3.利用绘制折线完成橡皮筋 4.采用右键菜单实现功能选择 -1. Learn the rubber bands rendering technology 2. Familiar with opengl programming process 3. Use draw line complete rubber band 4. The right menu selection function