Question

我用OPENGL画了个圆，请问如何用xy轴定义坐标呢代码如下

大神救我!,
一下是圆的代码
#include <windows.h>
#include <gl/glut.h>
#include <gl/glext.h>
#include <time.h>
#include<math.h>
const int n = 1000;
const GLfloat R = 0.5f;
const GLfloat Pi = 3.1415926536f;

void DrawCircle()
{
int i;
glBegin(GL_LINE_LOOP);
for(i=0; i<n; ++i)
glVertex2f(R*cos(2*Pi/n*i), R*sin(2*Pi/n*i));
glEnd();
glFlush();
}
void myDisplay()
{
glClear(GL_COLOR_BUFFER_BIT);
DrawCircle();
}

int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowPosition(100, 100);
glutInitWindowSize(400, 400);
glutCreateWindow("Draw a circle");
glutDisplayFunc(myDisplay);
glutMainLoop();
return 0;
}

Answer 1

#include <windows.h>
#include <glut.h>
#include <glext.h>
#include <time.h>
#include<math.h>
const int n = 1000;
const GLfloat R = 0.5f;
const GLfloat Pi = 3.1415926536f;

void DrawCircle()
{
int i;
glBegin(GL_LINE_LOOP);
for(i=0; i<n; ++i)
glVertex2f(R*cos(2*Pi/n*i), R*sin(2*Pi/n*i));
glEnd();

glBegin(GL_LINES);
glColor3f(1, 0, 0);
glVertex3f(0, 0, 0);
glVertex3f(1.2*R, 0, 0);

glColor3f(0, 1, 0);
glVertex3f(0, 0, 0);
glVertex3f(0, 1.2*R, 0);
glEnd();
glFlush();
}
void myDisplay()
{
glClear(GL_COLOR_BUFFER_BIT);
DrawCircle();
}

int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowPosition(100, 100);
glutInitWindowSize(400, 400);
glutCreateWindow("Draw a circle");
glutDisplayFunc(myDisplay);
glutMainLoop();
return 0;
}
楼主你试试这个代码，是你想要的吗？红色为X轴，绿色为Y轴。