一月16
OpenGL-海龜作圖法
海龜作圖法(Turtle Graphics)，意思是模仿海龜移動的方式，只能前進及左右轉，而將海龜的尾巴當作畫筆，可以放下及抬起。
本範例為二維空間，使用 OpenGL 搭配 C++ 實做。
程式功能介紹：
1、由 turtle.txt 檔案讀入作圖指令。
2、INIT - 設定海龜初始位置。(x 軸, y 軸, 龜頭角度)
3、PEN - 設定尾巴狀態。(0 抬起 / 1放下)
4、FW - 海龜向前移動。(移動長度)
5、RIGHT - 海龜右轉角度。(角度)
6、LEFT - 海龜左轉角度。(角度)
#include <iostream>
#include <fstream>
#include <cstring>
#include <cmath>
#include <GL/glut.h>
using namespace std;
const GLfloat PI = 3.141593;
class Turtle {
private:
bool penStatus, a;
GLfloat x1, y1, x2, y2; //座標
GLfloat cAngle; //角度
public:
Turtle() //constractor
{
penStatus = 0;
x1 = y1 = x2 = y2 = 0.0;
cAngle = 0.0;
a = 0;
}
/* 設定海龜位置 */
void InitPoint(GLfloat x, GLfloat y, GLfloat angle)
{
x1 = x; y1 = y; cAngle = angle; a = 1;
if (penStatus) //如果 pen down 應該畫出一點
{
glBegin(GL_POINTS);
glVertex2f(x, y);
glEnd();
}
}
/* 海龜向前移動 */
void forward(GLfloat L)
{
x2 = x1 + L * cos(cAngle*PI/180);
y2 = y1 + L * sin(cAngle*PI/180);
if (penStatus)
{
glBegin(GL_LINES);
glVertex2f(x1, y1);
glVertex2f(x2, y2);
glEnd();
}
x1 = x2; y1 = y2;
}
/* 海龜右轉角度 */
void right(GLfloat angle)
{
cAngle = (a) ? cAngle - angle : angle;
a = 1;
}
/* 海龜左轉角度 */
void left(GLfloat angle)
{
cAngle = (a) ? cAngle + angle : angle;
a = 1;
}
/* 設定畫筆狀態(0 up/1 down) */
void setPen(bool value)
{
penStatus = value;
if (value) //pen down 畫出一點
{
glBegin(GL_POINTS);
glVertex2f(x1, y1);
glEnd();
}
}
};
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT); /*clear the window */
char cmd[10];
float x, y, angle;
bool p;
ifstream fp("turtle.txt");
Turtle t;
while (!fp.eof())
{
fp >> cmd;
if (!strcmp(cmd, "INIT")) {
fp >> x >> y >> angle;
t.InitPoint(x, y, angle);
} else if (!strcmp(cmd, "FW")) {
fp >> x;
t.forward(x);
} else if (!strcmp(cmd, "RIGHT")) {
fp >> x;
t.right(x);
} else if (!strcmp(cmd, "LEFT")) {
fp >> x;
t.left(x);
} else if (!strcmp(cmd, "PEN")) {
fp >> p;
t.setPen(p);
}
}
glFlush(); /* clear buffers */
}
int main(int argc, char** argv)
{
/* Standard GLUT initialization */
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); /* default, not needed */
glutInitWindowSize(500, 500); /* 500 x 500 pixel window */
glutInitWindowPosition(0, 0); /* place window top left on display */
glutCreateWindow("Turtle Graphics"); /* window title */
glutDisplayFunc(display); /* display callback invoked when window opened */
/* attributes */
glClearColor(1.0, 1.0, 1.0, 1.0); /* white background */
glColor3f(1.0, 0.0, 0.0); /* draw in red */
/* set up viewing */
/* 500 x 500 window with origin lower left */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, 500.0, 0.0, 500.0);
glMatrixMode(GL_MODELVIEW);
glutMainLoop(); /* enter event loop */
return 0;
}
#include <fstream>
#include <cstring>
#include <cmath>
#include <GL/glut.h>
using namespace std;
const GLfloat PI = 3.141593;
class Turtle {
private:
bool penStatus, a;
GLfloat x1, y1, x2, y2; //座標
GLfloat cAngle; //角度
public:
Turtle() //constractor
{
penStatus = 0;
x1 = y1 = x2 = y2 = 0.0;
cAngle = 0.0;
a = 0;
}
/* 設定海龜位置 */
void InitPoint(GLfloat x, GLfloat y, GLfloat angle)
{
x1 = x; y1 = y; cAngle = angle; a = 1;
if (penStatus) //如果 pen down 應該畫出一點
{
glBegin(GL_POINTS);
glVertex2f(x, y);
glEnd();
}
}
/* 海龜向前移動 */
void forward(GLfloat L)
{
x2 = x1 + L * cos(cAngle*PI/180);
y2 = y1 + L * sin(cAngle*PI/180);
if (penStatus)
{
glBegin(GL_LINES);
glVertex2f(x1, y1);
glVertex2f(x2, y2);
glEnd();
}
x1 = x2; y1 = y2;
}
/* 海龜右轉角度 */
void right(GLfloat angle)
{
cAngle = (a) ? cAngle - angle : angle;
a = 1;
}
/* 海龜左轉角度 */
void left(GLfloat angle)
{
cAngle = (a) ? cAngle + angle : angle;
a = 1;
}
/* 設定畫筆狀態(0 up/1 down) */
void setPen(bool value)
{
penStatus = value;
if (value) //pen down 畫出一點
{
glBegin(GL_POINTS);
glVertex2f(x1, y1);
glEnd();
}
}
};
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT); /*clear the window */
char cmd[10];
float x, y, angle;
bool p;
ifstream fp("turtle.txt");
Turtle t;
while (!fp.eof())
{
fp >> cmd;
if (!strcmp(cmd, "INIT")) {
fp >> x >> y >> angle;
t.InitPoint(x, y, angle);
} else if (!strcmp(cmd, "FW")) {
fp >> x;
t.forward(x);
} else if (!strcmp(cmd, "RIGHT")) {
fp >> x;
t.right(x);
} else if (!strcmp(cmd, "LEFT")) {
fp >> x;
t.left(x);
} else if (!strcmp(cmd, "PEN")) {
fp >> p;
t.setPen(p);
}
}
glFlush(); /* clear buffers */
}
int main(int argc, char** argv)
{
/* Standard GLUT initialization */
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); /* default, not needed */
glutInitWindowSize(500, 500); /* 500 x 500 pixel window */
glutInitWindowPosition(0, 0); /* place window top left on display */
glutCreateWindow("Turtle Graphics"); /* window title */
glutDisplayFunc(display); /* display callback invoked when window opened */
/* attributes */
glClearColor(1.0, 1.0, 1.0, 1.0); /* white background */
glColor3f(1.0, 0.0, 0.0); /* draw in red */
/* set up viewing */
/* 500 x 500 window with origin lower left */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, 500.0, 0.0, 500.0);
glMatrixMode(GL_MODELVIEW);
glutMainLoop(); /* enter event loop */
return 0;
}
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