渲染多边形和填充多边形

填充多边形：调整 glBegin(GL_POLYGON);
#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>

//////////////////////////////////
void myInit()
{
glClearColor(1.0,1.0,1.0,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,640,0.0,480);
}
/////////////////////////////////////
void myDisplay()
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0f, 0.f, 0.f);
glEnable(GL_LINE_SMOOTH);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
glBegin(GL_POLYGON);
glVertex2d(200, 20);
glVertex2d(100, 300);
glVertex2d(400, 500);
glVertex2d(300, 70);
glEnd();
glFlush();

}
///////////////////////////////////////
void main(int argc,char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(640,480);
glutInitWindowPosition(100,150);
glutCreateWindow("my second attempt");
glutDisplayFunc(myDisplay);
myInit();
glutMainLoop();
}

渲染空心多边形：调整 glBegin(GL_LINE_LOOP);
#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>

//////////////////////////////////
void myInit()
{
glClearColor(1.0,1.0,1.0,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,640,0.0,480);
}
/////////////////////////////////////
void myDisplay()
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0f, 0.f, 0.f);
glEnable(GL_LINE_SMOOTH);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
glLineWidth(10);
glBegin(GL_LINE_LOOP);
glVertex2d(200, 20);
glVertex2d(100, 300);
glVertex2d(400, 500);
glVertex2d(300, 70);
glEnd();
glFlush();

}
///////////////////////////////////////
void main(int argc,char **argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(640,480);
glutInitWindowPosition(100,150);
glutCreateWindow("my second attempt");
glutDisplayFunc(myDisplay);
myInit();
glutMainLoop();
}