计算机图形学实验——直线和圆的绘制

实验目的

1.本次实验着重学习以下常用函数，在实验报告中的实验原理部分对下列函数进行参数介绍和用法介绍。
glBegin(GL_POINTS)
glVertex() 绘制一个点
glEnd();
glLoadIdentity();
设置投影参数:
glMatrixMode(GL_PROJECTION);
视景体裁剪（创建一个正交平行的视景体，即正投影）：
glOrtho(left, right, bottom, top, near, far);
2.数字微分法（DDA）绘制一条直线，直线起点坐标为（-100，-100），终点为（50，20）。中点Brensenham算法绘制一条直线，直线起点坐标为（-100，-100），终点为（50，-10）
3.用中点Bresenham算法绘制一个圆心点在（0,0），半径为20的圆
4.绘制棋盘

实验结果

最终结果通过改变main函数中glutDisplayFunc();决定展示哪一个效果

#include<gl/glut.h>
#include<cmath>
void dda(float x1, float y1, float  x2, float y2);
void MidpointLine(float xs, float ys, float xe, float ye);
void ManyGlVertex2f(float absX, float absY, float x, float y);
void Bresenham(float xs, float ys, float xe, float ye);
void pnarc(float radius, float m, float n);
void bresenham_arc(float R, float m, float n);
void myinit(void);
//直线DDA法
void dda(float x1, float y1, float  x2, float y2) {
	float k, i;
	float x, y, dx, dy;
	k = fabsf(x2 - x1);
	if (fabsf(y2 - y1) > k)
		k = fabsf(y2 - y1);
	dx = float(x2 - x1) / k;
	dy = float(y2 - y1) / k;
	x = float(x1);
	y = float(y1);
	for (i = 0.0; i < k; i++) {
		glVertex2f(x, y);
		x = x + dx;
		y = y + dy;
	}
}
void Display1(void) {
	glClear(GL_COLOR_BUFFER_BIT);
	glPointSize(2.0);
	glColor3f(1.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	dda(-100, -100, 50, 20);
	glEnd();
	glFlush();
}
//直线正负法
void MidpointLine(float xs, float ys, float xe, float ye) {
	float a, b, dt1, dt2, d, x, y;
	float absY = ye - ys;
	float absX = xe - xs;
	//采用对称的方法来绘画其他象限的图案
	if ((fabsf(absY) > fabsf(absX)) && absX > 0 && absY > 0) {//斜率大于1
		float  m = ys;
		ys = xs;
		xs = m;
		float n = ye;
		ye = xe;
		xe = n;
	}
	else if (absY < 0 && absX>0 && (fabsf(absY) <= fabs(absX))) {
		ys = -ys;
		ye = -ye;
	}
	else if (absY < 0 && absX>0 && (fabsf(absY) > fabs(absX))) {
		float  m = ys;
		ys = xs;
		xs = -m;
		float n = ye;
		ye = xe;
		xe = -n;
	}
	else {//斜率0到1
		  //do nothing 
	}
	a = ys - ye;
	b = xe - xs;
	d = 2 * a + b;
	dt1 = 2 * a;
	dt2 = 2 * (a + b);
	x = xs; y = ys;
	ManyGlVertex2f(absX, absY, x, y);
	while (x < xe) {
		if (d < 0) {
			x++;
			y++;
			d = d + dt2;
		}
		else {
			x++; d = d + dt1;
		}
		ManyGlVertex2f(absX, absY, x, y); //调用ManyGlVertex2f()函数

	}
	//float maxY = getMax(ys, ye);
	//float minY = getMin(ys, ye);
	////画竖直的线
	//if (xs == xe) {
	//	for (float i = minY; i <= maxY; i++) {
	//		glVertex2f(xs, i);
	//	}
	//}

}
void ManyGlVertex2f(float absX, float absY, float x, float y) {
	if ((fabsf(absY) > fabsf(absX)) && absX > 0 && absY > 0) {//斜率大于1
		glVertex2f(y, x);
	}
	else if (absY < 0 && absX>0 && (fabsf(absY) <= fabs(absX))) {//斜率-1到0
		glVertex2f(x, -y);
	}
	else if (absY < 0 && absX>0 && (fabsf(absY) > fabs(absX))) {//斜率小于-1
		//printf("到这了\n");
		glVertex2f(y, -x);
	}
	else {//斜率0到1
		glVertex2f(x, y);
	}
}
void Display2(void) {
	glClear(GL_COLOR_BUFFER_BIT);//注意这几个glClear等函数放的位置
	glPointSize(2.0);
	glColor3f(1.0, 0.0, 0.0);/*用红色绘制对象*/
	glBegin(GL_POINTS);
	MidpointLine(-250, 250, 350, 200);
	MidpointLine(50, -150, 350, 250);
	MidpointLine(-450, 50, 0, 400);
	MidpointLine(-570, 0, 570, 0);//x轴
	MidpointLine(0, -570, 0, 570);//y轴
	glEnd();
	glFlush();
}
//直线Bresenham法
void Bresenham(float xs, float ys, float xe, float ye) {
	float absY = ye - ys;
	float absX = xe - xs;
	//采用对称的方法来绘画其他象限的图案
	if ((fabsf(absY) > fabsf(absX)) && absX > 0 && absY > 0) {//斜率大于1
		float  m = ys;
		ys = xs;
		xs = m;
		float n = ye;
		ye = xe;
		xe = n;
	}
	else if (absY < 0 && absX>0 && (fabsf(absY) <= fabs(absX))) {//斜率-1到0
		ys = -ys;
		ye = -ye;
	}
	else if (absY < 0 && absX>0 && (fabsf(absY) > fabs(absX))) {//斜率小于-1
		float  m = ys;
		ys = xs;
		xs = -m;
		float n = ye;
		ye = xe;
		xe = -n;
		/*printf("xs=%f\n", xs);
		printf("ys=%f\n", ys);
		printf("xe=%f\n", xe);
		printf("ye=%f\n", ye);*/

	}
	else {//斜率0到1
		  //do nothing 
	}
	float dx = xe - xs;
	float dy = ye - ys;
	float m = (double)dy / (double)dx;
	float e = m - 0.5;
	float x, y;
	x = xs;
	y = ys;
	for (int i = 0; i < dx; i++) {
		ManyGlVertex2f(absX, absY, x, y); //调用ManyGlVertex2f()函数
		if (e >= 0) {
			y = y + 1; e = e - 1;
		}
		x = x + 1; e = e + m;
	}
}
void Display3(void) {
	glClear(GL_COLOR_BUFFER_BIT);//注意这几个glClear等函数放的位置
	glPointSize(2.0);

	glColor3f(1.0, 0.0, 0.0);/*用红色绘制对象*/
	glBegin(GL_POINTS);
	Bresenham(-100, -100, 50, -10);
	//Bresenham(50, 150, 350, 250);
	//Bresenham(-450, 50, 0, -400);
	//Bresenham(-570, 0, 570, 0);//x轴
	//Bresenham(0, -570, 0, 570);//y轴
	dda(-100, -100, 50, 20);
	glEnd();
	glFlush();
}
//正负法
void pnarc(float radius, float m, float n) {
	float x, y, f;
	x = 0; y = 0 + radius; f = 0;
	while (y > 0) {
		glVertex2f(x + m, y + n);
		glVertex2f(-x + m, y + n);
		glVertex2f(-x + m, -y + n);
		glVertex2f(x + m, -y + n);
		if (f > 0) {
			f = f - 2 * y + 1; y = y - 1;
		}
		else {
			f = f + 2 * x + 1; x = x + 1;
		}
	}
	if (y == 0) {
		glVertex2f(x + m, y + n);
		glVertex2f(-x + m, y + n);
		glVertex2f(-x + m, -y + n);
		glVertex2f(x + m, -y + n);

	}
}
void Display4(void) {
	glClear(GL_COLOR_BUFFER_BIT);//注意这几个glClear等函数放的位置
	glPointSize(2.0);
	glColor3f(1.0, 0.0, 0.0);/*用红色绘制对象*/
	glBegin(GL_POINTS);
	pnarc(150, -250, 250);
	pnarc(150, 250, 250);
	pnarc(150, 250, -250);
	pnarc(150, -250, -250);

	Bresenham(-570, 0, 570, 0);//x轴
	Bresenham(0, -570, 0, 570);//y轴
	glEnd();
	glColor3f(0, 1, 0);
	glBegin(GL_POINTS);
	pnarc(150, 0, 0);
	glEnd();

	glFlush();
}
//Bresenham法
void bresenham_arc(float R, float m, float n) {
	float x, y, d;
	x = 0; y = R; d = 3 - 2 * R;
	while (x < y) {
		glVertex2f(x + m, y + n);
		glVertex2f(y + m, x + n);
		glVertex2f(y + m, -x + n);
		glVertex2f(x + m, -y + n);
		glVertex2f(-x + m, -y + n);
		glVertex2f(-y + m, -x + n);
		glVertex2f(-y + m, x + n);
		glVertex2f(-x + m, y + n);
		if (d < 0)
			d = d + 4 * x + 6;
		else {
			d = d + 4 * (x - y) + 10;
			y = y - 1;
		}
		x = x + 1;

	}
	if (x == y) {
		glVertex2f(x + m, y + n);
		glVertex2f(y + m, x + n);
		glVertex2f(y + m, -x + n);
		glVertex2f(x + m, -y + n);
		glVertex2f(-x + m, -y + n);
		glVertex2f(-y + m, -x + n);
		glVertex2f(-y + m, x + n);
		glVertex2f(-x + m, y + n);
	}
}
void Display5(void) {
	glClear(GL_COLOR_BUFFER_BIT);
	glPointSize(2.0);
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	bresenham_arc(20, 0, 0);
	glEnd();
	glFlush();
}
//调用以上函数绘制中国象棋的棋盘和棋子
void Display6(void) {
	glClear(GL_COLOR_BUFFER_BIT);
	glPointSize(2.0);
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	for (float i = -360; i <= 360; i += 80) {
		dda(-360, i, 360, i);
	}
	for (float i = -360; i <= 360; i += 90) {
		dda(i, 40, i, 360);
	}
	for (float i = -360; i <= 360; i += 90) {
		dda(i, -40, i, -360);
	}
	dda(-360, -40, -360, 40);
	dda(360, -40, 360, 40);
	float b = 90, c = 200, d = 360;
	dda(-b, c, b, d);
	dda(-b, d, b, c);
	dda(-b, -d, b, -c);
	dda(-b, -c, b, -d);
	glEnd();
	//画象棋图上的圆
	glColor3f(1.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	float R = 28;
	for (float i = -360; i <= 360; i += 90) {
		pnarc(R, i, 360);
		pnarc(R, i, -360);
	}
	for (float i = -360; i <= 360; i += 180) {
		pnarc(R, i, 120);
		pnarc(R, i, -120);
	}
	for (float i = -270; i <= 320; i += 540) {
		pnarc(R, i, 200);
		pnarc(R, i, -200);
	}
	glEnd();
	//最外侧直线
	glPointSize(3.0);
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_POINTS);
	float a = 380;
	dda(-a, a, a, a);
	dda(a, a, a, -a);
	dda(a, -a, -a, -a);
	dda(-a, -a, -a, a);
	glEnd();
	glFlush();
}
//设置属性
void myinit(void) {
	glClearColor(1.0, 1.0, 0.0, 0.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-500.0, 500.0, -500.0, 500.0);
	glMatrixMode(GL_MODELVIEW);
}
int main(int argc, char * argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
	glutInitWindowPosition(20, 40);		//设置位置
	glutInitWindowSize(280, 280);		//设置高宽
	glutCreateWindow("OpenGL");
	myinit();
	glutDisplayFunc(Display6);
	glutMainLoop();
	return 0;
}