写在前面：
1.本篇文章将解决 freeglut.h 和 glut.h两个库在VS2019下的配置问题，并解决三个OpenGL课本上的三个问题：
利用OpenGL实现折线和矩形的橡皮筋绘制技术，并采用右键菜单实现功能的选择。
利用OpenGL，分别用点和折线模式实现正弦和余弦曲线的绘制。
利用OpenGL程序绘制实线、虚线和点画线。
此外，还将绘制一个三角形。
代码参考：
问题一代码：
#include "freegult.h"
int iPointNum = 0;
int iMode = 0;
int x1 = 0, y1 = 0, x2 = 0, y2 = 0;
int width = 500, height = 500;
void MousePlot(GLint button, GLint action, GLint xMouse, GLint yMouse) {
if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN) {
if (iPointNum == 0 || iPointNum == 2) {
iPointNum = 1;
x1 = xMouse;
y1 = height - yMouse;
} else {
iPointNum = 2;
x2 = xMouse;
y2 = height - yMouse;
glutPostRedisplay();
}
}
}
void PassiveMouseMove(GLint xMouse, GLint yMouse) {
if (iPointNum == 1) {
x2 = xMouse;
y2 = height - yMouse;
glutPostRedisplay();
}
}
void ProcessMenu(int value) {
iMode = value;
x1 = 0;
y1 = 0;
x2 = 0;
y2 = 0;
glutPostRedisplay();
}
void processNormalKeys(unsigned char key, int x, int y) {
switch (key) {
case 99:
iMode = 0;
iPointNum = 0;
break;
case 27:
exit(0);
}
glutPostRedisplay();
}
void myinit(void) {
glClearColor(1.0, 1.0, 1.0, 1.0);
glutCreateMenu(ProcessMenu);
glutAddMenuEntry("line", 1);
glutAddMenuEntry("broken_line", 2);
glutAddMenuEntry("rectangle", 3);
glutAttachMenu(GLUT_RIGHT_BUTTON);
}
void myReshape(GLsizei w, GLsizei h) {
width = w;
height = h;
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, width, 0.0, height);
}
void display(void) {
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0, 0.0, 0.0);
if (iMode == 1) {
glBegin(GL_LINES);
glVertex2i(x1, y1);
glVertex2i(x2, y2);
glEnd();
} else if (iMode == 2) {
glBegin(GL_LINE_STRIP);
glVertex2i(x1, y1);
glVertex2i(x2, y1);
glVertex2i(x2, y2);
glEnd();
} else if (iMode == 3) {
glBegin(GL_LINE_LOOP);
glVertex2i(x1, y1);
glVertex2i(x2, y1);
glVertex2i(x2, y2);
glVertex2i(x1, y2);
glEnd();
}
glutSwapBuffers();
}
int main(int argc, char* argv[]) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow("luoxiaoc");
myinit();
glutKeyboardFunc(processNormalKeys);
glutMouseFunc(MousePlot);
glutPassiveMotionFunc(PassiveMouseMove);
glutReshapeFunc(myReshape);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
问题二代码：
#include <GL/freeglut.h>
#include <math.h>
#define PI 3.1416
int winWidth = 500, winHeight = 500;
void myinit(void) {
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
}
void myReshape(int w, int h) {
winWidth = w;
winHeight = h;
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, w, 0.0, h);
}
void display(void) {
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.0, 1.0, 0.0);
glBegin(GL_LINES);
glVertex2f(0, 250.0);
glVertex2f(500.0, 250.0);
glVertex2f(250.0, 0);
glVertex2f(250.0, 500.0);
glEnd();
glColor3f(1.0, 0.0, 0.0);
glTranslatef(250, 250, 0);
glBegin(GL_POINTS);
for (float x = -PI; x < PI; x += 2 * PI / 180) {
float y = sin(x);
glVertex2f(50 * x, 50 * y);
}
glEnd();
glBegin(GL_LINE_STRIP);
for (float x = -PI; x < PI; x += 2 * PI / 180) {
float y = sin(x);
glVertex2f(50 * x, 50 * y);
}
glEnd();
glBegin(GL_POINTS);
for (float x = -PI; x < PI; x += 2 * PI / 180) {
float y = cos(x);
glVertex2f(50 * x, 50 * y);
}
glEnd();
glBegin(GL_LINE_STRIP);
for (float x = -PI; x < PI; x += 2 * PI / 180) {
float y = cos(x);
glVertex2f(50 * x, 50 * y);
}
glEnd();
glutSwapBuffers();
}
int main(int argc, char* argv[]) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
glutInitWindowSize(500, 500);
glutInitWindowPosition(100, 100);
glutCreateWindow("");
myinit();
glutReshapeFunc(myReshape);
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
【注】display函数中四个画线函数每次运行一个即可；
问题三代码：
#include "glut.h"
void init() {
glClearColor(1.0, 1.0, 1.0, 1.0);
glColor3f(0.0, 0.0, 0.0);
glLineWidth(2.0);
}
void display() {
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_LINES);
glVertex2f(-0.9, 0.8);
glVertex2f(0.9, 0.8);
glEnd();
glEnable(GL_LINE_STIPPLE);
glLineStipple(1, 0x00FF);
glBegin(GL_LINES);
glVertex2f(-0.9, 0.5);
glVertex2f(0.9, 0.5);
glEnd();
glDisable(GL_LINE_STIPPLE);
glEnable(GL_LINE_STIPPLE);
glLineStipple(1, 0x1C47);
glBegin(GL_LINES);
glVertex2f(-0.9, 0.2);
glVertex2f(0.9, 0.2);
glEnd();
glDisable(GL_LINE_STIPPLE);
glFlush();
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(800, 600);
glutInitWindowPosition(100, 100);
glutCreateWindow("Line Styles in OpenGL");
init();
glutDisplayFunc(display);
glutMainLoop();
return 0;
}
三角形代码：
#include "freeglut.h"
const GLsizei windowWidth = 800;
const GLsizei windowHeight = 800;
// This function renders the scene using OpenGL.
void RenderScene() {
// Clear the frame buffer by setting it to the clear color.
glClear(GL_COLOR_BUFFER_BIT);
// Select the Modelview Matrix and reset it to its default state.
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// Draw the triangle.
glBegin(GL_TRIANGLES);
glColor3f(1.0, 0.0, 0.0); // red
glVertex2f(0.0, 1.0);
glColor3f(0.0, 1.0, 0.0); // green
glVertex2f(1.0, -1.0);
glColor3f(0.0, 0.0, 1.0); // blue
glVertex2f(-1.0, -1.0);
glEnd();
// Flush the graphic buffers &
// swap them (double buffering).
glFlush();
glutSwapBuffers();
}
// This is the entry point of the program.
int main(int argc, char* argv[]) {
// Initialize GLUT.
glutInit(&argc, argv);
// Set the display mode to use double buffering.
// GLUT_SINGLE will came flichering.
glutInitDisplayMode(GLUT_DOUBLE);
// Create a window with the title "Hello OpenGL".
int windowID = glutCreateWindow("Hello OpenGL");
glutReshapeWindow(windowWidth, windowHeight);
// Set the display function to render the scene.
glutDisplayFunc(RenderScene);
// Set the clear color to white.
glClearColor(1.0, 1.0, 1.0, 1.0);
// Transfer control over to GLUT.
glutMainLoop();
// This code is never reached.
return 0;
}
参考链接：
三角形代码：三角形绘制；
环境配置：先看（从头看到精准空降的这里），然后退出来把这个视频看完安装库。
问题一参考；
问题二参考；