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c++ - 如何在 glfw 中 glutDisplayFunc、glutMainLoop？

问题描述

我有一个使用 glut 的小程序，我现在需要使用 glfw 有很多原因。由于我从未使用过 glfw，我遇到了很多问题。主要的功能是：glutDisplayFunc、、glutReshapeFunc和glutIdleFuncglutMainLoop。我刚刚发现glfw中没有等效的功能。我应该如何修改我的程序？

我的程序是关于一个 3 维旋转的锥体

我有一个功能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();

}

一个功能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
}

和一个功能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，我有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();

标签： c++openglglfwopengl-compat

解决方案

使用glfw时，您必须创建自己的应用程序循环。请注意，在调用任何 OpenGL 指令之前，通过glfwMakeContextCurrent. 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();
}

而不是glutReshapeFunc您可以通过以下方式设置大小回调glfwSetWindowSizeCallback：例如： 

glfwSetWindowSizeCallback(wnd, reshapeCone);

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

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