OpenGL入门实例(3)-多边形细节

时间：2014-02-26 05:07:59 阅读：442 评论：0 收藏：0 [点我收藏+]

1.菜单

OpenGL 自己有设置菜单的函数,这对于一直写控制台程序的我来说,显的非常好玩.下面的代码,我们定义了一个鼠标右键的特性,

可以下拉两个菜单,清屏和退出.

#include <GL/glut.h>
#include <stdio.h>
#include <cmath>


 




void mymenu(int value)
{
	if(value == 1)
	{
		glClear(GL_COLOR_BUFFER_BIT);
		glutSwapBuffers();//or glFlush()
		glutAttachMenu(GLUT_RIGHT_BUTTON);
	}
	if(value == 2)
		exit(0);
}
void init()
{
	glutCreateMenu(mymenu);//添加菜单,要得到菜单项的整数值
	glutAddMenuEntry("Clear Screen",1);//
	glutAddMenuEntry("Exit",2);
	glutAttachMenu(GLUT_RIGHT_BUTTON);//绑定到鼠标键
}
int main(int argc,char **argv)
{
    glutInit(&argc,argv);
    glutCreateWindow("Hello,world!");
 //   glutDisplayFunc(display);//glutDisplayFunc(void (*func)(void))
    glClear(GL_COLOR_BUFFER_BIT);
	init();
    glutMainLoop();//导致程序进入一个事件
}

2.将菜单和一个五角星综合起来

#include <GL/glut.h>
#include <stdio.h>
#include <cmath>
const GLfloat Pi = 3.1415926536f;

void display()//欠缺几何方面的知识
{
     GLfloat a = 1 / (2-2*cos(72*Pi/180));
     GLfloat bx = a * cos(18 * Pi/180);
     GLfloat by = a * sin(18 * Pi/180);
     GLfloat cy = -a * cos(18 * Pi/180);
     GLfloat
         PointA[2] = { 0, a },
         PointB[2] = { bx, by },
         PointC[2] = { 0.5, cy },
         PointD[2] = { -0.5, cy },
         PointE[2] = { -bx, by };

     glClear(GL_COLOR_BUFFER_BIT);
     // 按照A->C->E->B->D->A的顺序，可以一笔将五角星画出
     glBegin(GL_LINE_LOOP);
         glVertex2fv(PointA);
         glVertex2fv(PointC);
         glVertex2fv(PointE);
         glVertex2fv(PointB);
         glVertex2fv(PointD);
     glEnd();
     glFlush();
}




void mymenu(int value)
{
	if(value == 1)
	{
		glClear(GL_COLOR_BUFFER_BIT);
		glutSwapBuffers();//or glFlush()
		glutAttachMenu(GLUT_RIGHT_BUTTON);
	}
	if(value == 2)
		exit(0);
}
void init()
{
	glutCreateMenu(mymenu);//添加菜单,要得到菜单项的整数值
	glutAddMenuEntry("Clear Screen",1);//
	glutAddMenuEntry("Exit",2);
	glutAttachMenu(GLUT_RIGHT_BUTTON);//绑定到鼠标键
}
int main(int argc,char **argv)
{
    glutInit(&argc,argv);
    glutCreateWindow("Hello,world!");
    glutDisplayFunc(display);//glutDisplayFunc(void (*func)(void))
    //glClear(GL_COLOR_BUFFER_BIT);
	init();
    glutMainLoop();//导致程序进入一个事件
}

3.如何渲染多边形

启动函数,主要我是看看他们放在什么位置,注意正反面

//多边形类型
#include<GL/glut.h>
#include<stdio.h>
void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glPolygonMode(GL_FRONT,GL_FILL);//设置正面为填充模式
	glPolygonMode(GL_BACK,GL_LINE);//设置反面为线性模式
	glFrontFace(GL_CW);//设置逆时针方向为正面
	glBegin(GL_POLYGON);//按逆时针绘制一个正方形,在左下方
		glVertex2f(-0.5,-0.5);
		glVertex2f(0.0,0.5);
		glVertex2f(0.0,0.0);
		glVertex2f(-0.5,0.0);
	glEnd();
	glBegin(GL_POLYGON);//按顺 dram a recent
		glVertex2f(0.0,0.0);
		glVertex2f(0.0,0.5);
		glVertex2f(0.5,0.5);
		glVertex2f(0.5,0.0);
	glEnd();
	glFlush();

		
}
int main(int argc,char** argv)
{
	glutInit(&argc,argv);
	glutCreateWindow("NNN");
	glutDisplayFunc(display);
	glutMainLoop();
}

4.如何渲染正反面,注意函数的位置

//多边形类型
#include<GL/glut.h>
#include<stdio.h>
void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glPolygonMode(GL_FRONT,GL_FILL);//设置正面为填充模式
	glPolygonMode(GL_BACK,GL_LINE);//设置反面为线性模式
	glFrontFace(GL_CCW);//
	glEnable(GL_CULL_FACE);//开启特性
	glCullFace(GL_BACK);//指定隐藏的那面
	glBegin(GL_POLYGON);//按逆时针绘制一个正方形,在左下方
		glVertex2f(-0.5,-0.5);
		glVertex2f(0.0,0.5);
		glVertex2f(0.0,0.0);
		glVertex2f(-0.5,0.0);
	glEnd();
	glBegin(GL_POLYGON);//按顺 dram a recent
		glVertex2f(0.0,0.0);
		glVertex2f(0.0,0.5);
		glVertex2f(0.5,0.5);
		glVertex2f(0.5,0.0);
	glEnd();
	glDisable(GL_CULL_FACE);//关闭特性
	glFlush();

		
}
int main(int argc,char** argv)
{
	glutInit(&argc,argv);
	glutCreateWindow("NNN");
	glutDisplayFunc(display);
	glutMainLoop();
}

bubuko.com,布布扣