Visual C++ 7.1Visual C++ 8.0Windows VistaVisual C++ 7.0C++/CLIWin32Visual Studio 2005Visual C++ 6.0初学者C开发Visual StudioWindowsC++
简单的 OpenGL 2D 原始图形 EP_OpenGL_002
2D 基本 OpenGL 图形原语：线条、点、三角形、四边形和多边形
引言
这是一个简单的 OpenGL 程序，展示了如何绘制二维 OpenGL 图形原语，例如 GL_POINT、GL_LINES、GL_TRIANGLES、GL_QUADS、GL_POLYGON。它基于“OpenGL 编程指南第三版”。它使用了 GLUT.h 库。
背景
我不会详细解释 OpenGL 或 GLUT。有很多好的资源详细解释了这些主题。我的目标是展示这个主题的一个可运行版本。
Using the Code
如果您尚未安装 GLUT.h 库，则此程序将无法工作。如果您不知道如何安装它，可以阅读我的第一篇文章，其中我解释了如何安装 GLUT.h。
安装 GLUT.h 库后，只需编译并执行代码即可。
安装 GLUT.h 库后，您必须在代码中包含它 (#include<GL/glut.h>)。
这里还有一个用户定义的全局函数的示例 (drawOneLine(x1,y1,x2,y2))
#include "stdafx.h"
#include <GL/glut.h>
GLfloat X = 0.0f; // Translate screen to x direction (left or right)
GLfloat Y = 0.0f; // Translate screen to y direction (up or down)
// A function to draw a line
#define drawOneLine(x1,y1,x2,y2) glBegin(GL_LINES); \
glVertex2f ((x1),(y1)); glVertex2f ((x2),(y2)); glEnd();
所有图形原语都在这里绘制 (display(void))
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
gluOrtho2D (-1.1, 1.1 , -1.1 , 1.1); // Displays the OpenGL window area
// from (x1,y1,x2,y2)
glTranslatef(X, Y, 0.0f); // Moves (translates) the screen left
// to right and up or down
glutPostRedisplay();
glColor3f(1.0,1.0,1.0);
// This lines are the two main lines for the coordinate system
// The crossing point of the line is the (0,0,0)
// Since its just 2 dimensional z is 0
glBegin(GL_LINES);
glVertex3f(-1.0, 0.0, 0.0);
glVertex3f(1, 0.0, 0.0);
glVertex3f(0.0, -1.0, 0.0);
glVertex3f(0.0, 1.0, 0.0);
glEnd();
// Example of some line stipple
glEnable (GL_LINE_STIPPLE);
glLineStipple (1, 0x0101); /* dotted */
drawOneLine (-0.1, 1, -1, 1);
glLineStipple (1, 0x00FF); /* dashed */
drawOneLine (-0.1, 0.9, -1, 0.9);
glLineStipple (1, 0x1C47); /* dash/dot/dash */
drawOneLine (-0.1, 0.8, -1, 0.8);
/* in 2nd row, 3 wide lines, each with different stipple */
glLineWidth (5.0);
glLineStipple (1, 0x0101); /* dotted */
drawOneLine (-0.1, 0.7, -1, 0.7);
glLineStipple (1, 0x00FF); /* dashed */
drawOneLine (-0.1, 0.6, -1, 0.6);
glLineStipple (1, 0x1C47); /* dash/dot/dash */
drawOneLine (-0.1, 0.5, -1, 0.5);
glLineWidth (1.0);
glDisable (GL_LINE_STIPPLE);
// Just basic lines (wrote E my names initial)
glBegin(GL_LINES);
glVertex2f(-1.0, 0.4);
glVertex2f(-1.0, 0.1);
glVertex2f(-1.0, 0.4);
glVertex2f(-0.8, 0.4);
glVertex2f(-1.0, 0.25);
glVertex2f(-0.8, 0.25);
glVertex2f(-1.0, 0.1);
glVertex2f(-0.8, 0.1);
glEnd();
// Example of Line Strip
// The end of the previous line is the beginning of the next line
// The program connects the points for you basically you save time
glBegin(GL_LINE_STRIP);
glVertex2f(-0.6,0.3);
glVertex2f(-0.3,0.2);
glVertex2f(-.65, 0.2);
glVertex2f(-0.4, 0.05);
glEnd();
// Example of Line Loop
// Its similar to the line strip however at the end it connects the last point
// with the beginning point
glBegin(GL_LINE_LOOP);
glVertex2f(-0.65,0.45);
glVertex2f(-0.1,0.4);
glVertex2f(-0.1, 0.1);
glVertex2f(-0.4, 0.4);
glEnd();
// Example of points
glBegin(GL_POINTS);
glVertex3f(0.1, 0.1, 0.0);
glVertex3f(0.1, 0.2, 0.0);
glVertex3f(0.1, 0.3, 0.0);
glVertex3f(0.1, 0.4, 0.0);
glVertex3f(0.1, 0.5, 0.0);
glVertex3f(0.1, 0.6, 0.0);
glVertex3f(0.1, 0.7, 0.0);
glVertex3f(0.1, 0.8, 0.0);
glVertex3f(0.1, 0.9, 0.0);
glVertex3f(0.1, 1.0, 0.0);
glEnd();
// Example of triangles
glBegin(GL_TRIANGLES);
glVertex3f(0.2, 1.0, 0.0);
glVertex3f(0.5, 1.0, 0.0);
glVertex3f(0.35, 0.6, 0.0);
glEnd();
// Example of triangle strip
glBegin(GL_TRIANGLE_STRIP);
glVertex3f(0.2, 0.5, 0.0);
glVertex3f(0.2, 0.1, 0.0);
glVertex3f(0.4, 0.3, 0.0);
glVertex3f(0.5, 0.4, 0.0);
glVertex3f(0.4, 0.1,0.0);
glEnd();
// Example of triangle fan
glBegin(GL_TRIANGLE_FAN);
glVertex3f(0.5, 0.5, 0.0);
glVertex3f(0.5, 0.7, 0.0);
glVertex3f(0.6, 0.6, 0.0);
glVertex3f(0.7, 0.5, 0.0);
glVertex3f(0.6, 0.4,0.0);
glEnd();
// Example of quads
glBegin(GL_QUADS);
glVertex3f(-1, -0.2, 0.0);
glVertex3f(-0.6, -0.2, 0.0);
glVertex3f(-0.5, -0.50, 0.0);
glVertex3f(-0.8, -0.75, 0.0);
glEnd();
// Example of quad strips
glBegin(GL_QUAD_STRIP);
glVertex3f(-0.1, -0.1, 0.0);
glVertex3f(-0.3, -0.1, 0.0);
glVertex3f(-0.124, -0.4, 0.0);
glVertex3f(-0.27, -0.3, 0.0);
glVertex3f(-0.35, -0.6, 0.0);
glVertex3f(-0.4, -0.5, 0.0);
glEnd();
// Example of polygon
glBegin(GL_POLYGON);
glVertex3f(0.10, -0.25, 0.0);
glVertex3f(0.7, -0.3, 0.0);
glVertex3f(1, -0.50, 0.0);
glVertex3f(0.6, -0.8, 0.0);
glVertex3f(0.3, -0.6, 0.0);
glEnd();
// Don't wait start processing buffered OpenGL routines
glFlush();
}
使用两个函数从关键字获取用户输入。如果用户按下 'q' 或 'Q'，程序将退出。如果用户按下箭头键，窗口将向左或向右、向上或向下平移。
// Function to determine which key is pressed
// Will be passed to glutKeyboardFunc(keyCB);
void keyCB(unsigned char key, int x, int y) /* called on key press */
{
// if 'q' is pressed exit the program
if( key == 'q' || key == 'Q')
exit(0);
}
// Similar function like keyCB; determines which special key is pressed
// Will be passed to glutSpecialFunc(specialKey);
void specialKey(int key, int x, int y) { // called on special key pressed
// Check which (arrow) key is pressed
switch(key) {
case GLUT_KEY_LEFT : // Arrow key left is pressed
X -= 0.1f;
break;
case GLUT_KEY_RIGHT : // Arrow key right is pressed
X += 0.1f;
break;
case GLUT_KEY_UP : // Arrow key up is pressed
Y += 0.1f;
break;
case GLUT_KEY_DOWN : // Arrow key down is pressed
Y -= 0.1f;
break;
}
主函数
// Main point of the program
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(600,600); // Size of the OpenGL window
glutCreateWindow("OpenGL 2 Dimensional Geometries"); // Creates OpenGL Window
glutDisplayFunc(display);
glutKeyboardFunc(keyCB); // set window's key callback
glutSpecialFunc(specialKey); // set window's to specialKey callback
glutMainLoop();
return 0;
}