放射线

代码如下：

#include <windows.h>
//#include <GLUT/glut.h>
#include <GL/glut.h>
#include <math.h>
#include <iostream>
using namespace std;

#define GL_PI 3.1415f

void RenderScene()
{
    GLfloat sizes[2];
    GLfloat step;
    GLfloat curSize;

    glClear(GL_COLOR_BUFFER_BIT);

    glGetFloatv(GL_POINT_SIZE_RANGE,sizes);
    glGetFloatv(GL_POINT_SIZE_GRANULARITY,&step);

    curSize = sizes[0];

    GLfloat x,y,angle;
    glBegin(GL_LINES);
    for(angle = 0.0f;angle <= GL_PI;angle += 0.1f)
    {
        x = 50.0f*sin(angle);
        y = 50.0f*cos(angle);
        glVertex2f(x,y);

        x = 50.0f*sin(angle+GL_PI);
        y = 50.0f*cos(angle+GL_PI);
        glVertex2f(x,y);
    }
    glEnd();
    glFlush();
}

void ChangeSize(GLsizei w,GLsizei h)
{
    if(h==0)
        h = 1;

    GLfloat aspectRatio = (GLfloat)w/(GLfloat)h;

    glViewport(0,0,w,h);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    if(w<=h)
        glOrtho(-100,100,-100/aspectRatio,100/aspectRatio,1.0,-1.0);
    else
        glOrtho(-100*aspectRatio,100*aspectRatio,-100,100,1.0,-1.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

}

void SetupRC()
{
    glClearColor(0.0f,0.0f,0.0f,1.0f);
    glColor3f(1.0f,0.0f,0.0f);
}

int main(int argc, char *argv[])
{
   glutInit(&argc,argv);
   glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
   glutInitWindowSize(800,600);
   glutCreateWindow("Simple");

   glutDisplayFunc(RenderScene);
   glutReshapeFunc(ChangeSize);

   SetupRC();
   glutMainLoop();
   return 0;
}