OpenGL绘制简单的参数曲线——三阶Bezier曲线（二）

#include <math.h>  
#include <gl/glut.h>  
#include <iostream>
using namespace std;

GLfloat xCoord[4], yCoord[4];  
int num = 0;  

/*计算Bezier曲线*/
void Bezier(int n) 
{  
	float f1, f2, f3, f4;  
	float deltaT = 1.0 / n; 
	float T;

	glBegin(GL_LINE_STRIP);  
	for (int i = 0; i <= n; i++) {  

		T = i * deltaT;

		f1 = (1-T) *(1- T) * (1-T);  
		f2 = 3 * T * (1-T) * (1- T);  
		f3 = 3 * T * T * (1-T);  
		f4 = T * T * T;  

		glVertex2f( f1*xCoord[0] + f2*xCoord[1] + f3*xCoord[2] + f4*xCoord[3],  
			f1*yCoord[0] + f2*yCoord[1] + f3*yCoord[2] + f4*yCoord[3]);  
	}  
	glEnd();  
}  

/*用鼠标进行绘制，完成后可改变控制点，
	wsad控制第二个控制点，ijkl控制第三个控制点*/
void display(){  
	glClear(GL_COLOR_BUFFER_BIT);  

	glLineWidth(1.5);
	glColor3f (1.0, 0.0, 0.0);  
	glBegin(GL_LINE_STRIP);  
	for (int i = 0; i < num; i++)  
		glVertex3f (xCoord[i], yCoord[i], 0.0);  
	glEnd();  

	glColor3f (0.0, 0.0, 1.0);  
	if (num == 4)  
		Bezier(20);  

	glFlush();
	glutSwapBuffers();
}  

void init()
{  
	glClearColor(1.0, 1.0, 1.0, 0.0);  
	glShadeModel(GL_FLAT); 
}  

void myReshape(int w, int h)  
{  
	glViewport(0, 0, (GLsizei)w, (GLsizei)h);  
	glMatrixMode(GL_PROJECTION);  
	glLoadIdentity();  
	gluOrtho2D(0.0, (GLsizei)w, (GLsizei)h, 0.0);  
	glMatrixMode(GL_MODELVIEW);  
	glLoadIdentity();  
}  

void mouse(int button, int state, int x, int y)  
{  
	if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) 
	{  
		if (num == 4) 
			num = 0;  

		xCoord[num] = x;  
		yCoord[num] = y;  
		num++;  
		glutPostRedisplay();  
	}  
}  

void keyboard(unsigned char key, int x, int y)
{
	if (key == ‘w‘ && num == 4)
		yCoord[1] -= 5.0;

	if (key == ‘s‘ && num == 4)
		yCoord[1] += 5.0;

	if (key == ‘a‘ && num == 4)
		xCoord[1] -= 5.0;

	if (key == ‘d‘ && num == 4)
		xCoord[1] += 5.0;

	if (key == ‘i‘ && num == 4)
		yCoord[2] -= 5.0;

	if (key == ‘k‘ && num == 4)
		yCoord[2] += 5.0;

	if (key == ‘j‘ && num == 4)
		xCoord[2] -= 5.0;

	if (key == ‘l‘ && num == 4)
		xCoord[2] += 5.0;

	glutPostRedisplay();
}

int  main(int argc, char** argv)  
{  
	glutInit(&argc, argv);  
	glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB );  
	glutInitWindowSize (450, 450);  
	glutInitWindowPosition (200, 200);  
	glutCreateWindow ("hello");  
	init ();  

	glutDisplayFunc(display);  
	glutReshapeFunc(myReshape);  
	glutKeyboardFunc(keyboard);
	glutMouseFunc(mouse);  

	glutMainLoop();  
	return 0;  
}