How to glutDisplayFunc, glutMainLoop in glfw?

Question

I have a small program using glut and i need for many reasons to use glfw now. Since I have never used glfw I have a lot of problems. The main ones are the functions : glutDisplayFunc, glutReshapeFunc, glutIdleFunc and glutMainLoop. I have just found out that there are no equivalent functions in glfw. How should I modify my program ?

My program is about a cone rotating in 3 dimensions

I have a function 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();

}

a function 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
}

and a function 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();

    }
}

In my previous program i had in 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();

Rabbid76 · Accepted Answer · 2019-08-03T12:38:00.693

5

When using glfw, then you've to create your own application loop. Note, it is important to to make the OpenGL context current, before calling any OpenGL instruction, by glfwMakeContextCurrent. e.g.:

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();
}

Instead of glutReshapeFunc you can set the size callback by glfwSetWindowSizeCallback: e.g.:

glfwSetWindowSizeCallback(wnd, reshapeCone);

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

edited Aug 03 '19 at 12:38

answered Aug 03 '19 at 11:35

Rabbid76

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when I compile I get : note: crosses initialization of 'GLFWwindow* wnd' – Jatos Aug 03 '19 at 14:08
@Jatos Sorry, but I can't see your actual code nor do I know in which line the error occurs. I the line `GLFWwindow *wnd = glfwCreateWindow(...)` in a `switch` statement? – Rabbid76 Aug 03 '19 at 14:10
Now i solved it by putting GLFWwindow out of the switch statement. When I compile the code on mac terminal says Undefined symbols for architecture x86_64: "_glfwCreateWindow", referenced from: _main in ccR3zGkL.o – Jatos Aug 03 '19 at 15:25
@Jatos Possibly [OpenGL 3.3/4.1 on Mac OSX 10.9 using GLFW library](https://stackoverflow.com/questions/23450334/opengl-3-3-4-1-on-mac-osx-10-9-using-glfw-library) can help – Rabbid76 Aug 03 '19 at 15:47

How to glutDisplayFunc, glutMainLoop in glfw?

1 Answers1