#include<GL/freeglut.h>

void mouseWheel(int button, int dir, int x, int y)
{

    printf("in mouse wheel n");

    if (dir > 0)
    {
        // Zoom in
        ztrans = ztrans - 1.0;
        printf("scroll in = %0.3fn ",ztrans);
    }
    else
    {
        // Zoom out
        ztrans = ztrans + 1.0;
        printf("scroll out = %0.3fn ",ztrans);
    }

        glutPostRedisplay();

}

    int main(int argc, char **argv)
    {
      // general initializations
      glutInit(&argc, argv);
      glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
      glutInitWindowPosition(100, 100);
      glutInitWindowSize(800, 400);
      glutCreateWindow("Rotation");

      // register callbacks
      glutReshapeFunc(changeSize);
      glutDisplayFunc(renderScene);
      glutIdleFunc(renderScene);
      glutIgnoreKeyRepeat(1);
      glutMouseFunc(mouseButton);
      glutMotionFunc(mouseMove);
      glutMouseWheelFunc(mouseWheel); // Register mouse wheel function

      glEnable(GL_DEPTH_TEST);

      glutMainLoop();
      return 0;

static int k;
static int ztrans
void mouseWheel(int button, int dir, int x, int y)
{

   k = dir; // int dir is +1 of -1 based on the direction of the wheel motion

   ztrans = ztrans + k;

}