OpenGL动态绘制Brezier曲线|OpenGL

#include 
#include
#pragma comment(linker, "/subsystem:\"windows\" /entry:\"mainCRTStartup\"")
int SCREEN_HEIGHT = 600;
int NUMPOINTS = 0;
class Point
{
	public:
	float x, y;
	void setxy(float x2, float y2)
	{
		x = x2;
		y = y2;
	}
};
Point abc[4];
Point bef[3];
Point mid[2];
Point link[1000];


void myInit()
{
	glClearColor(0.0, 0.0, 0.0, 0.0);
	glColor3f(1.0f, 0.0, 0.0);
	glPointSize(4.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0, 640, 0.0, 480.0);
}
void drawDot(Point pt)
{
	glBegin(GL_POINTS);
	glVertex2f(pt.x, pt.y);
	glEnd();
	glFlush();
	}
	void drawLine(Point p1, Point p2)
	{
	glBegin(GL_LINES);
	glVertex2f(p1.x, p1.y);
	glVertex2f(p2.x, p2.y);
	glEnd();
	glFlush();
}
//四个控制点的贝塞尔曲线 即三次Bezier曲线  
void drawBezier(Point A, Point B, Point C, Point D)
{
	for (double t = 0.0; t <= 1.0; t += 0.001)
	{
		bef[0].setxy((1 - t)*A.x + t*B.x, (1 - t)*A.y + t*B.y);
		bef[1].setxy((1 - t)*B.x + t*C.x, (1 - t)*B.y + t*C.y);
		bef[2].setxy((1 - t)*C.x + t*D.x, (1 - t)*C.y + t*D.y);
		
		
		mid[0].setxy((1 - t)*bef[0].x + t*bef[1].x, (1 - t)*bef[0].y + t*bef[1].y);
		mid[1].setxy((1 - t)*bef[1].x + t*bef[2].x, (1 - t)*bef[1].y + t*bef[2].y);
		
		
		link[0].setxy((1 - t)*mid[0].x + t*mid[1].x, (1 - t)*mid[0].y + t*mid[1].y);
		
		glColor3f(1.0f, 1.0f, 0.0f);
		drawLine(bef[0], bef[1]);
		glColor3f(1.0f, 1.0f, 0.0f);
		drawLine(bef[1], bef[2]);
		glColor3f(1.0f, 1.0f, 0.0f);
		drawLine(mid[0], mid[1]);
		
		glColor3f(1.0f, 0.0f, 0.0f);
		drawDot(link[0]);
		
		glColor3f(0.0f, 0.0f, 0.0f);
		drawLine(bef[0], bef[1]);
		glColor3f(0.0f, 0.0f, 0.0f);
		drawLine(bef[1], bef[2]);
		glColor3f(0.0f, 0.0f, 0.0f);
		drawLine(mid[0], mid[1]);
	
	
	
	
	glColor3f(0.0, 1.0, 0.0);
	drawLine(abc[0], abc[1]);
	glColor3f(0.0, 1.0, 0.0);
	drawLine(abc[1], abc[2]);
	glColor3f(0.0, 1.0, 0.0);
	drawLine(abc[2], abc[3]);
	}
}


void myDisplay()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glFlush();
}


void ChangeSize(GLsizei width, GLsizei height)
{
	GLfloat aspect_init, aspect;
	glViewport(0, 0, width, height);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	aspect_init = 4.0 / 3.0;
	aspect = 1.0*width / height;
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	//Keep Aspect of Current Window
	if (aspect <= aspect_init)
	glViewport(0, (height - width / aspect) / 2, width, width / aspect_init);
	else
	glViewport((width - height*aspect_init) / 2, 0, height*aspect_init, height);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glOrtho(-2, 2, -2, 2, -2, 2);

}






void myMouse(int button, int state, int x, int y)
{
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
{
	abc[NUMPOINTS].setxy((float)x, (float)(SCREEN_HEIGHT - y));
	NUMPOINTS++;
	if (NUMPOINTS == 4)
	{
		glColor3f(1.0, 0.0, 1.0);
		drawDot(abc[0]);
		glColor3f(1.0, 0.0, 1.0);
		drawDot(abc[1]);
		glColor3f(1.0, 0.0, 1.0);
		drawDot(abc[2]);
		glColor3f(1.0, 0.0, 1.0);
		drawDot(abc[3]);

		glColor3f(0.0, 1.0, 0.0);
		drawLine(abc[0], abc[1]);
		glColor3f(0.0, 1.0, 0.0);
		drawLine(abc[1], abc[2]);
		glColor3f(0.0, 1.0, 0.0);
		drawLine(abc[2], abc[3]);
		//Point POld = abc[0];
		
		drawBezier(abc[0], abc[1], abc[2], abc[3]);
		glColor3f(1.0, 0.0, 1.0);
		drawDot(abc[0]);
		glColor3f(0.0, 1.0, 0.0);
		drawLine(abc[0], abc[1]);
		glColor3f(0.0, 1.0, 0.0);
		drawLine(abc[1], abc[2]);
		glColor3f(0.0, 1.0, 0.0);
		drawLine(abc[2], abc[3]);
		glColor3f(1.0, 0.0, 0.0);
		NUMPOINTS = 0;
	}
	}
}


void main(int argc, char **argv)
{
	glutInit(&argc, argv);
	
	// 在这里设置双缓冲区。        
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowPosition(0, 0);
	glutInitWindowSize(800, 600);
	glutCreateWindow("bezier");
	glutMouseFunc(myMouse);
	
	myInit();
	//glutIdleFunc(RenderScene);
	glutDisplayFunc(myDisplay);
	glutMainLoop();
}