OpenGL C ++类型为void的参数与类型为void（*）（）的参数不兼容

Question

I am trying to draw several triangles in 3d and can't execute glutDisplayFunc() function. Here is my code:

Array of triangles and size.

int const trsize = (size-1)*(size-1)*2;
Triangle *trarr = new Triangle[trsize];

Code, where I try to call the function.

glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
glutInitWindowSize(400,400);        
glutInitWindowPosition(100,100);    
glutCreateWindow("Height Map");     
Initialize();                       
glutDisplayFunc(Draw1(trarr, trsize));              
glutMainLoop();

Draw1() function.

void Draw1(Triangle arr[], int size){
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0, 1.0, 1.0);
    glBegin(GL_LINES);
    for(int i=0; i<size; ++i){
        glVertex3d((GLdouble)arr[i].p1().x(), (GLdouble)arr[i].p1().y(), (GLdouble)arr[i].p1().z());
        glVertex3d((GLdouble)arr[i].p2().x(), (GLdouble)arr[i].p2().y(), (GLdouble)arr[i].p2().z());
        glVertex3d((GLdouble)arr[i].p3().x(), (GLdouble)arr[i].p3().y(), (GLdouble)arr[i].p3().z());
    }
    glEnd();
    glFlush();
}

I use VS2012 and IntelliSense writes: argument of type "void" is incompatible with parameter of type "void (*)()"

I don't know why DisplayFunc needs another type. With Draw() function without arguments it works fine.

Answer 1

glutDisplayFunc only allow function with that signature: void func(void).

so in you code, your drawing routine should be:

void Draw1(void){...}

and you should find another way (global variable for example) to pass parameters to it. And your glut statement would be:

glutDisplayFunc(Draw1);

Answer 2

those parameters should be globals that you assign to as you set the drawFunc:

Triangle arr[];
int size;

void Draw1(){
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0, 1.0, 1.0);
    glBegin(GL_LINES);
    for(int i=0; i<size; ++i){
        glVertex3d((GLdouble)arr[i].p1().x(), (GLdouble)arr[i].p1().y(), (GLdouble)arr[i].p1().z());
        glVertex3d((GLdouble)arr[i].p2().x(), (GLdouble)arr[i].p2().y(), (GLdouble)arr[i].p2().z());
        glVertex3d((GLdouble)arr[i].p3().x(), (GLdouble)arr[i].p3().y(), (GLdouble)arr[i].p3().z());
    }
    glEnd();
    glFlush();
}


Initialize();         
arr = trarr; size = trsize;              
glutDisplayFunc(Draw1);              
glutMainLoop();

it's a shortcoming of the glut library that you have to use globals to pass data around the callbacks