直线

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()
{
    glClear(GL_COLOR_BUFFER_BIT);

    GLfloat sizes[2];
    GLfloat step;

    glGetFloatv(GL_LINE_WIDTH_RANGE,sizes);
    glGetFloatv(GL_LINE_WIDTH_GRANULARITY,&step);

    GLfloat curSize = sizes[0];
    GLfloat x,y;
    x = -50,y = -90;

    for(int i = 0;i < 9;i++)
    {
        glLineWidth(curSize);
        glBegin(GL_LINES);
        glVertex2f(x,y);
        glVertex2f(-x,y);
        glEnd();

        curSize += 1.0f;
        y += 20.0f;
    }
    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,100.0,-100.0);
    else
        glOrtho(-100*aspectRatio,100*aspectRatio,-100,100,100.0,-100.0);

    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;
}