在OpenGL中,如何调整窗口的大小?

您肯定不想让对象的大小显式地依赖于窗口大小。

正如genpfault所建议的,只要窗口大小改变,就调整投影矩阵。

调整窗口大小时的操作:

1. glViewport(0, 0, width, height)
   

2. 调整剪刀矩形 (如果你有 GL_SCISSOR_TEST 已启用)

   glScissor(0, 0, width, height)
   

3. 调整投影矩阵

   如果是传统的(固定功能管道)OpenGL,可以通过以下方式进行:

   glFrustum(left * ratio, right * ratio, bottom, top, nearClip,farClip)
   

   或

   glOrtho(left * ratio, right * ratio, bottom, top, nearClip,farClip)
   

   或

   gluOrtho2D(left * ratio, right * ratio, bottom, top)
   

   left, right, bottom top 都是平等的 ratio=width/height )

如果您使用的是glupperspective()之类的工具,只需使用窗宽/高比:

gluPerspective(60, (double)width/(double)height, 1, 256);

您应该设置某种窗口处理程序函数,每当调整OpenGL窗口的大小时都会调用该函数。当aspectRatio>1,当aspectRatio<=1分开。不这样做可能会导致几何图形在屏幕调整大小后落在屏幕之外。

void windowResizeHandler(int windowWidth, int windowHeight){
    const float aspectRatio = ((float)windowWidth) / windowHeight;
    float xSpan = 1; // Feel free to change this to any xSpan you need.
    float ySpan = 1; // Feel free to change this to any ySpan you need.

    if (aspectRatio > 1){
        // Width > Height, so scale xSpan accordinly.
        xSpan *= aspectRatio;
    }
    else{
        // Height >= Width, so scale ySpan accordingly.
        ySpan = xSpan / aspectRatio;
    }

    glOrhto2D(-1*xSpan, xSpan, -1*ySpan, ySpan, -1, 1);

    // Use the entire window for rendering.
    glViewport(0, 0, windowWidth, windowHeight);
}

我也在学习opengl。我昨天遇到了这个问题,但我没有找到正确的答案。今天,我已经解决了这个问题。在我的小程序中,当改变窗口的宽度或高度时,对象会改变大小。这是我的代码(请原谅我的错误):

#include <GL/freeglut.h>

void fnReshape(int ww, int hh)
{
  GLdouble r;
  if(hh == 0)
    hh = 1.0;
  if(hh > ww)
    r = (double) hh / (double) ww;
  else
    r = (double) ww / (double) hh;
  glViewport(0, 0, ww, hh);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  if(hh > ww)
    glFrustum(-1.0, 1.0, -1.0 * r, 1.0 * r, 2.0, 200.0);
  else
    glFrustum(-1.0 * r, 1.0 * r, -1.0, 1.0, 2.0, 200.0);
}
//////////////////////////////////////////////////////////////////
void fnDisplay(void)
{
  glClear(GL_COLOR_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glTranslatef(0., 0., -5.);
  glBegin(GL_QUAD_STRIP);
  glColor3f(0., 0., 1.0);
  glVertex3f(-1., -1., 0.);
  glVertex3f(-1., 1., 0.);
  glVertex3f(1., -1., 0.);
  glVertex3f(1., 1., 0.);
  glEnd();
  glutSwapBuffers();
}
////////////////////////////////////////////////////////////
int main(int argc, char **argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA |GLUT_DOUBLE);
    glutInitWindowSize(500, 500);
    glutCreateWindow("Sample window");
    glClearColor(1.0, 0, 0, 1.0);
    glutDisplayFunc(fnDisplay);
    glutReshapeFunc(fnReshape);
    glutMainLoop();
    return 0;
}

该示例仅显示一个矩形框,当窗口调整大小时,该框的大小不会改变。您可以直接复制并粘贴到您的项目中(假设我是openGl初学者)

#include<windows.h>
#include<glut.h>

GLfloat x1=100.0f;
GLfloat y1=150.0f;
GLsizei rsize = 50;

GLfloat xstep=1.0f;
GLfloat ystep=1.0f;

GLfloat windowWidth;
GLfloat windowHeight;


void scene(void){
   glClear(GL_COLOR_BUFFER_BIT);
   glColor3f(1.0f,0.0f,0.0f);

   glRectf(x1,y1,x1+rsize,y1-rsize);

   glutSwapBuffers();
}

void setupRc(void){

  glClearColor(0.0f,0.0f,1.0f,0.0f);

}

void changeSize(GLsizei w,GLsizei h){
  if(h==0)
  h=1;
  glViewport(0,0,w,h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
   if(w>=h){
     windowWidth=250.0f*w/h;
     windowHeight=250.f;
   }
   else{
     windowWidth=250.0f;
     windowHeight=250.f*h/w;
   } 

   glOrtho(0.0f,windowWidth,0.0f,windowHeight,1.0f,-1.0f);


   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();


}




void main(void){

   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);

   glutCreateWindow("Rectangle");

   glutReshapeFunc(changeSize);
   glutDisplayFunc(scene);
   setupRc();

   glutMainLoop();

}