前面1、2介绍的都是glut编程
下面就进行opengl正是部分啦。
1.绘制点
#include <iostream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
void myMainWinDraw();
int main(int argc,char** argv) {
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(400, 400);
glutInitWindowPosition(0, 0);
glutCreateWindow("Hello");
glutDisplayFunc(myMainWinDraw);
glutMainLoop();
return 0;
}
void myMainWinDraw(){
glClearColor(0.0,0.0,0.0,0.0);//设置清除色
glClear(GL_COLOR_BUFFER_BIT); //清除颜色缓冲区
float a[2];
glGetFloatv(GL_POINT_SIZE_RANGE,a);
std::cout<<a[0]<<"---"<<a[1]<<"\n"; //输出的是，点大小的范围（不过没有这么严格）
glPointSize(10); //设置点的大小
glBegin(GL_POINTS);
#if 0
(0.5f,0.4f);
(-0.5f,0.4f,0.0f);
(0.0f,-0.4f,0.0f);
#else
glColor3f(1.0f,0.0f,0.0f); //为点设置颜色
glVertex3f(0.5f,0.4f,0.0f); //该语句可绘制
glColor3f(0.0f,0.0f,1.0f);
glVertex3f(-0.5f,0.4f,0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(0.0f,-0.4f,0.0f);
#endif // 0
glEnd();
glFlush();
}
这里留下小思考题：
掷骰子是随机事件，现在平面上有三个点A、B、C，还有一个点P，位置可随机。令点A代表骰子的点数为1、4，点B代表骰子的点数为2、5，点C代表骰子的点数为3、6。现在开始扔，如果扔的点数为1或者4，那么取AP的中点作为新的P；如果扔到2或者5，则取BP的中点作为新的P；如果扔到的点数为3，6，则同理取CP的中点作为新的P。同时，要把每次取得的新的P绘制出来，并保持与相应的A或B或C同色。前面一定次数（如前20次），我们先不画点（还未进入稳态），后面再开始绘制。看看最终得到的图形是什么样子。
结果很奇妙！
明明是随机的，却呈现了规律性。赞叹数学、赞叹科学？是的，但我也想赞叹让我知道这个的我的老师。
2.绘制线
#include <iostream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
void myMainWinDraw();
int main(int argc,char** argv) {
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(400, 400);
glutInitWindowPosition(0, 0);
glutCreateWindow("Hello");
glutDisplayFunc(myMainWinDraw);
glutMainLoop();
return 0;
}
void myMainWinDraw(){
glClearColor(0.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT);
glLineWidth(2);
glBegin(GL_LINES);
#if 0
glVertex3f(0.5f,0.0f,0.0f);
glVertex3f(0.5f,0.4f,0.0f);
glVertex3f(0.0f,0.4f,0.0f);
glVertex3f(0.0f,-0.4f,0.0f);
#else
glColor3f(1.0f,0.0f,0.0f);
glVertex3f(0.5f,0.0f,0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(0.5f,0.4f,0.0f);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f(0.0f,0.4f,0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f(0.0f,-0.4f,0.0f);
#endif
glEnd();
glFlush();
}两点连成一条直线。点和点之间是配对的，如果给的点的个数是奇数，那么最后一个点没有找到和他配对的点，会不起作用。
关于颜色：
默认状态，是两边点颜色的线性插值，结果如下：
如果不想这样，就需要 glShadeModel(GL_FLAT) 变成：
glShadeModel(GL_SMOOTH) 和 glShadeModel(GL_FLAT) ！！
联系：绘制环
glBegin(GL_LINES_LOOP) :给出的两个相邻的点首尾相连，最后一个点和第一个点相连，构成环。两种颜色模式下：
3.绘制三角形
#include <iostream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
void myMainWinDraw();
int main(int argc,char** argv) {
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(400, 400);
glutInitWindowPosition(0, 0);
glutCreateWindow("Hello");
glutDisplayFunc(myMainWinDraw);
glutMainLoop();
return 0;
}
void myMainWinDraw(){
glClearColor(0.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT);
//glShadeModel(GL_FLAT); //GL_SMOOTH
glBegin(GL_TRIANGLES);
#if 0
glVertex3f(0.5f,0.0f,0.0f);
glVertex3f(0.5f,0.4f,0.0f);
glVertex3f(0.0f,0.4f,0.0f);
glVertex3f(0.0f,-0.4f,0.0f);
glVertex3f(0.3f,-0.4f,0.0f);
glVertex3f(0.0f,-0.2f,0.0f);
#else
glColor3f(1.0f,0.0f,0.0f);
glVertex3f(0.5f,0.0f,0.0f);
glColor3f(0.0f,1.0f,0.0f);
glVertex3f(0.5f,0.4f,0.0f);
glColor3f(1.0f,0.0f,0.0f);
glVertex3f(0.0f,0.4f,0.0f);
glColor3f(0.0f,0.0f,1.0f);
glVertex3f(0.0f,-0.4f,0.0f);
glColor3f(1.0f,0.0f,1.0f);
glVertex3f(0.3f,-0.4f,0.0f);
glColor3f(0.0f,1.0f,1.0f);
glVertex3f(0.0f,-0.2f,0.0f);
#endif
glEnd();
glFlush();
}三个点一组，绘制一个三角形。
推广：
（后面几个平时用不太到）
4.绘制的线型
#include <iostream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
void myMainWinDraw();
int main(int argc,char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(400, 400);
glutInitWindowPosition(0, 0);
glutCreateWindow("Hello");
glutDisplayFunc(myMainWinDraw);
glutMainLoop();
return 0;
}
void myMainWinDraw(){
glClearColor(0.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT);
glLineWidth(2);
glEnable(GL_LINE_STIPPLE);
glLineStipple(1,0xF0F0); //第一个参数是重复度、第二个参数代表线型
glBegin(GL_LINES);
glVertex3f(0.5f, 0.4f ,0.0f);
glVertex3f(-0.5f, 0.4f ,0.0f);
glEnd();
glLineWidth(10);
glLineStipple(5,0xF0F0);
glColor3f(1.0f,0.0f,0.0f);
glBegin(GL_LINES);
glVertex3f(0.5f, 0.0f, 0.0f);
glVertex3f(-0.5f, 0.0f,0.0f);
glEnd();
glLineWidth(20);
glLineStipple(3,0x7555);
glColor3f(1.0f,1.0f,0.0f);
glBegin(GL_LINES);
glVertex3f(0.5f, -0.4f, 0.0f);
glVertex3f(-0.5f, -0.8f,0.0f);
glEnd();
glLineWidth(5);
glBegin(GL_LINE_LOOP);
glVertex3f(-0.8f, 0.8f, 0.0f);
glVertex3f(-0.8f, -0.8f, 0.0f);
glVertex3f( 0.8f, -0.8f, 0.0f);
glVertex3f( 0.8f, 0.8f, 0.0f);
glEnd();
glFlush();
}
新的知识点：
1. glEnable(GL_LINE_STIPPLE) ：将开关打开
2. glLineStipple(1,0xF0F0）：第一个参数是重复度，第二个参数是线型。这里是，1111000011110000。如果将第一个参数改为2，那么将变成1111111100000000...这个样子。
绘制结果：
5.多边形绘制的模式（填充/线框）
#include <iostream>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
void myMainWinDraw();
int main(int argc,char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(400, 400);
glutInitWindowPosition(0, 0);
glutCreateWindow("Hello");
glutDisplayFunc(myMainWinDraw);
glutMainLoop();
return 0;
}
void myMainWinDraw(){
glClearColor(0.0,0.0,0.0,0.0);
glClear(GL_COLOR_BUFFER_BIT);
glDisable(GL_LIGHTING);
glPolygonMode(GL_FRONT,GL_FILL);
glPolygonMode(GL_BACK,GL_LINE);
glBegin(GL_TRIANGLES);
glVertex2f(-1.0f, 0.0f);
glVertex2f( 0.0f, 0.0f);
glVertex2f( 0.0f, 1.0f);
glEnd();
glPolygonMode(GL_FRONT,GL_LINE);
glBegin(GL_TRIANGLES);
glVertex2f( 1.0f, 0.0f);
glVertex2f( 0.0f, 1.0f);
glVertex2f( 0.0f, 1.0f);
glEnd();
glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
glBegin(GL_TRIANGLES);
glVertex2f( 0.0f, 0.0f);
glVertex2f( -1.0f, 0.0f);
glVertex2f( 0.0f,-1.0f);
glEnd();
glFrontFace(GL_CW);
glPolygonMode(GL_BACK,GL_FILL);
glPolygonMode(GL_FRONT,GL_LINE);
glBegin(GL_TRIANGLES);
glVertex2f( 0.0f, 0.0f);
glVertex2f( 0.0f,-1.0f);
glVertex2f( 1.0f, 0.0f);
glEnd();
glFlush();
}
新的知识点：
1. glPolygonMode(GL_FRONT,GL_FILL)：设置正面或者背面的填充方式为GL_FILL或者GL＿LINE模式。
2. glFrontFace(GL_CW)：初始状态将CCW方向（点的顺序）视为正面，该语句将CW方向转为正面。
6.多边形填充的效果
填充图形的定义：
下面就是glBegin()和glEnd() 了
