c++ - 如何在glfw中显示glutDisplayFunc，glutMainLoop？

Question

我有一个使用glut的小程序，出于很多原因，我现在需要使用glfw。由于我从未使用过glfw，所以存在很多问题。
主要的功能是:glutDisplayFunc，glutReshapeFunc，glutIdleFunc和glutMainLoop。我刚刚发现glfw中没有等效功能。我应该如何修改程序？

我的程序是关于3维旋转的圆锥体

我有一个函数displaycone:

void displayCone(void){

    // clear the drawing buffer.
    glClear(GL_COLOR_BUFFER_BIT);  //

    // set matrix mode
    glMatrixMode(GL_MODELVIEW);
    // clear model view matrix
    glLoadIdentity();
    // multiply view matrix to current matrix
    gluLookAt(3.0, 3.0, 3.0-4.5, 0.0, 0.0,-4.5,0,1,0);

    // ******
    glPushMatrix();


    glTranslatef(0.0, 0.0, -4.5);

    glBegin(GL_LINES);

    glColor3f (1.0, 1.0, 0.0);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(2.0, 0.0, 0.0);

    glColor3f (1.0, 1.0, 0.0);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(0.0, 2.0, 0.0);

    glColor3f (1.0, 1.0, 0.0);
    glVertex3f(0.0, 0.0, 0.0);
    glVertex3f(0.0, 0.0, 2.0);
    glEnd();

    glPopMatrix();

    // clear the drawing buffer.


    // traslate the draw by z = -4.0
    // Note this when you decrease z like -8.0 the drawing will looks far , or smaller.
    glTranslatef(0.0,0.0,-4.5);
    // Red color used to draw.
    glColor3f(0.8, 0.2, 0.1);
    // changing in transformation matrix.
    // rotation about X axis
    glRotatef(xRotated,1.0,0.0,0.0);
    // rotation about Y axis
    glRotatef(yRotated,0.0,1.0,0.0);
    // rotation about Z axis
    glRotatef(zRotated,0.0,0.0,1.0);

    // scaling transfomation
    glScalef(1.0,1.0,1.0);
    // built-in (glut library) function , draw you a Cone.

    // move the peak of the cone to the origin
    glTranslatef(0.0, 0.0, -height);

    glutSolidCone(base,height,slices,stacks);
    // Flush buffers to screen
    // gluLookAt(3,3,3,0,0,-4.5,0,1,0); <----------------------- delete

    glFlush();
    // sawp buffers called because we are using double buffering
    // glutSwapBuffers();

}

函数reshapecone:

void reshapeCone(int x, int y)
{
    if (y == 0 || x == 0) return;  //Nothing is visible then, so return
    //Set a new projection matrix
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    //Angle of view:40 degrees
    //Near clipping plane distance: 0.5
    //Far clipping plane distance: 20.0

    gluPerspective(35.0,(GLdouble)x/(GLdouble)y,0.5,20.0);

    glViewport(0,0,x,y);  //Use the whole window for rendering
}

和一个函数idleCone:

void idleCone(void)
{
    for(int j = 1; j<10000 ; j++){
        double i = dati[j+1][0];

        int win = glfwGetWindow();

        if(i == 0.)      break; 

        xRotated = 180/M_PI*(dati[j][0]);
        yRotated = 180/M_PI*(dati[j][1]);
        zRotated = 180/M_PI*(dati[j][2]);

        displayCone();
        xRotated += 0.;
        yRotated += 0.;
        zRotated += 0.;
        displayCone();

    }
}

在我以前的程序中，我使用main:

glfwInit(&argc, argv);
//double buffering used to avoid flickering problem in animation
glutInitDisplayMode(GLUT_SINGLE | GL_RGB);
//glfwInitWindowSize(800,700);

glfwCreateWindow(800,700,"Rotation of the top",NULL,NULL);
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
xRotated = yRotated = zRotated = 0.0;
xRotated=0.0;
yRotated=0.0;
glClearColor(0.0,0.0,0.0,0.0);

glutDisplayFunc(displayCone);
glutReshapeFunc(reshapeCone);
glutIdleFunc(idleCone);

glutMainLoop();  

Answer 1

使用glfw时，您必须创建自己的应用程序循环。请注意，在通过 glfwMakeContextCurrent 调用任何OpenGL指令之前，使OpenGL上下文成为当前状态非常重要。例如。:

GLFWwindow *wnd = glfwCreateWindow(800,700,"Rotation of the top",NULL,NULL);
glfwMakeContextCurrent(wnd);

// do the OpenGL initialization
// [...]

while (!glfwWindowShouldClose(wnd))
{
    // do the drawing
    displayCone();

    glfwSwapBuffers(wnd);
    glfwPollEvents();
}

除了glutReshapeFunc之外，您还可以通过 glfwSetWindowSizeCallback 设置大小回调:例如:

glfwSetWindowSizeCallback(wnd, reshapeCone);

void reshapeCone(GLFWwindow* window, int x, int y)
{
    // [...]
}