update README
update README

xupei0610/ComputerGraphics-HW,xupei0610/ComputerGraphics-HW,xupei0610/ComputerGraphics-HW,xupei0610/ComputerGraphics-HW,xupei0610/ComputerGraphics-HW,xupei0610/ComputerGraphics-HW,xupei0610/ComputerGraphics-HW