GLUT 滚轮缩放

Question

我已经浏览了很多资源并尝试了很多变体，但缩放仍然不起作用。我无法将 glprojection 更改为 gluPerspective，因为在这种情况下，我的程序不会绘制任何东西。这是大概的代码。

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
#include "glut.h"

#define windowSize 900.0
double zoomFactor = 1;
void reshape (int w, int h)
{
glViewport (0.0, 0.0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluOrtho2D (-(GLdouble) w * zoomFactor, (GLdouble) w* zoomFactor, -(GLdouble) h* zoomFactor, (GLdouble) h* zoomFactor);
}
void mouse(int button, int state, int x, int y)
{
      if (button == 3 || button == 4 )
   { 
       if (state == GLUT_UP) zoomFactor += 0.05;
else zoomFactor -= 0.05;
   }
   else return;
   glutReshapeFunc(reshape);
}

Void display(){
glClear(GL_COLOR_BUFFER_BIT);

glBegin(GL_LINES); 
glVertex2f ((0),(0)); 
glVertex2f ((100),(0));
 glEnd();
glBegin(GL_LINES); 
glVertex2f ((100),(0)); 
glVertex2f ((100),(100));
 glEnd();
glBegin(GL_LINES); 
glVertex2f ((0),(0)); 
glVertex2f ((100),(1000));
 glEnd();
glFlush();

}

int main(int argc,char** argv)
{
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize(windowSize, windowSize);
glutInitWindowPosition(500,0);
glutCreateWindow("test");
glClearColor(0, 0.1,0.8,0.90);    
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, 200, 200,0);   
glutDisplayFunc( display );    
glutMouseFunc(mouse);
glutMainLoop(;

return(0);
}

Answer 1

glutReshapeFunc 仅在 window 大小发生变化时告诉 GLUT 要调用哪个函数。调用它来响应输入事件几乎没有意义，因为它不会调用重塑函数。

无论如何，您的问题是，您在重塑函数中设置了视口和投影。致所有教程作者：停止这样做，这只会让新手养成坏习惯。

现在请和我说话："Everything drawing related goes into the display function. The viewport is a drawing state and in every OpenGL program just a little bit more complex than 'Hello Triangle' the viewport is going to be changed several times drawing a single frame – for example when using framebuffer objects. I will thereby vow to never place calls to glViewport or projection matrix setup in the window reshape handler. I also vow to slap everyone in the face who writes code like this in my presence."

将重塑函数中的全部内容移动到 display（设置全局变量，或使用 glutGet(GLUT_WINDOW_{WIDTH,HEIGHT}) 在显示函数中获取 window 维度）并调用 glutPostRedisplay 在你的鼠标滚轮函数中触发重绘。

GLUT 滚轮缩放

GLUT zooming in and out by wheel

opengl

glut

zooming