[OpenGL]课后案例05：生成正方形的程序

最新推荐文章于 2025-01-08 14:58:35 发布

原创最新推荐文章于 2025-01-08 14:58:35 发布 · 1.6k 阅读

0 ·

CC 4.0 BY-SA版权

计算机图形学专栏收录该内容

32 篇文章

订阅专栏

本文介绍了一个使用GLUT库实现的简单图形程序，该程序可以在窗口中绘制出随着鼠标点击位置变化颜色和位置的正方形。同时，程序能够响应窗口的移动和缩放事件，并重新调整视口。

//A.5  生成正方形的程序
/* This program illustrates the use of the GLUT library for
interfacing with a Window System */
/* The program opens a window, clears it to black,
then draws a box at the location of the mouse each time the
left button is clicked. The right button exits the program.
The program also reacts correctly when the window is
moved or resized by clearing the new window to black.  */
#include <GL/glut.h>
#include <stdlib.h>
/* globals */
GLsizei wh = 500, ww = 500; /* initial window size */
GLfloat size = 3.0;   /* half side length of square */
void drawSquare(int x, int y)
{
    y=wh-y;
    glColor3ub( (char) rand()%256, (char) rand()%256, (char) rand()
        %256);
    glBegin(GL_POLYGON);
    glVertex2f(x+size, y+size);
    glVertex2f(x-size, y+size);

    glVertex2f(x-size, y-size);
    glVertex2f(x+size, y-size);
    glEnd();
    glFlush();
}
/* reshaping routine called whenever window is resized
or moved */
void myReshape(GLsizei w, GLsizei h)
{
    /* adjust clipping box */
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, (GLdouble)w, 0.0, (GLdouble)h, -1.0, 1.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    /* adjust viewport and clear */
    glViewport(0,0,w,h);
    glClear(GL_COLOR_BUFFER_BIT);
    glFlush();
    /* set global size for use by drawing routine */
    ww = w;
    wh = h;
}
void myinit(void)
{
    glViewport(0,0,ww,wh);
    /* Pick 2D clipping window to match size of screen window.
    This choice avoids having to scale object coordinates

    each time window is resized. */
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0, (GLdouble) ww, 0.0, (GLdouble) wh, -1.0, 1.0);
    /* set clear color to black and clear window */
    glClearColor (0.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);
    glFlush();
}
void mouse(int btn,int state,int x,int y)
{
    if(btn==GLUT_RIGHT_BUTTON &&state==GLUT_DOWN)  exit(0);
}
/* display callback required by GLUT*/
void display()
{}
int main(int argc,char** argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
    glutCreateWindow("square");
    myinit();
    glutReshapeFunc (myReshape);
    glutMouseFunc (mouse);
    glutMotionFunc (drawSquare);
    glutDisplayFunc (display);
    glutMainLoop();
}