what is the use of this function (in need of line to line explaination)

void add_UFO(void)
int i;
for (i = 0; i < MAX_UFO; i++)
if (UFO[i].speed == 0)

  UFO[i].speed = ((float) (random() % 20)) * 0.0001 + 0.02;
  if (random() & 0x1)
  UFO[i].speed *= -1;
  UFO[i].theta = ((float) (random() % 257)) * 0.1111;
  if (!moving)
  glutPostRedisplay();      /*Request redisplay*/


A line by line explanation will not be of any use to you if you can’t understand that basic chunk of code. I assume you’re just starting out with programing and lack OOP concepts. It has nothing to do with the subforum, anyway: (i.e. “Discussion about 3D math and linear algebra that is essential as a background to OpenGL coding”). I suggest starting with some programming tutorials/books.

The only non-standard code part in there is the glutPostRedisplay() line and that already has an explanation about what it does right next to it.

actually I’m having problem in this below function,by mistake i pasted the above one…

void tick_per_UFO(int i)
float theta = UFO[i].theta += UFO[i].speed;
UFO[i].z = -9 + 4 * cos(theta);
UFO[i].x = 4 * sin(2 * theta);
UFO[i].y = sin(theta / 3.4) * 3;
UFO[i].angle = (((2.0) + M_PI_2) * sin(theta) - M_PI_2) * 180 / M_PI; /calculates nor of degrees using nor of radians/
if (UFO[i].speed < 0.0)
UFO[i].angle += 180;

That didn’t change the problem: your code doesn’t appear to have anything to do with OpenGL.

yes u r rt. sir!!!But it is part of openGl function which hv written using basic language.only my problem is about those x,y,z axis.