I currently have an earth and a moon. What I'm trying to achieve is to have the moon physically rotate around the earth horizontally along the equator along a circular path.

    moonAngle = (moonAngle + 0.5f) % 360f;
    xPath = (float) Math.sin(Math.toRadians(moonAngle)) * distance;
    yPath = (float) Math.cos(Math.toRadians(moonAngle)) * distance;

    gl.glTranslatef(xPath, yPath, -30f);

The above works fine, except the moon is rotating around the earth vertically around the Prime Meridian like a wall clock. How do I adjust the angle of rotation? I've tried modifying the glTranslatef, but with no success.

  • \$\begingroup\$ What do you mean, exactly, with horizontal and vertical rotation? The first thing that comes to my mind with "horizontal rotation" is the rotationing at the start of this video: youtube.com/watch?v=LoQYw49saqc \$\endgroup\$
    – Mutoh
    Commented Jan 13, 2013 at 23:07
  • 3
    \$\begingroup\$ Aren’t you just confusing Y and Z in the glTranslatef call? \$\endgroup\$ Commented Jan 13, 2013 at 23:42
  • \$\begingroup\$ @SamHocevar The problem is that I'm trying to maintain the z-position of -30f at the same time why moving along the X and Z paths which is also the same position as the zPosition as the earth. This way if I move the Earth along the zAxis, the moon will update accordingly as well. \$\endgroup\$
    – ChocoMan
    Commented Jan 13, 2013 at 23:56
  • 1
    \$\begingroup\$ @ChocoMan Then you might want to try gl.glTranslatef(xPath, 0f, yPath-30f);. But most of all you want to remove hardcoded values and use named variables for the Earth position. \$\endgroup\$ Commented Jan 14, 2013 at 0:13
  • 1
    \$\begingroup\$ Okay, I made it into an answer, but I think the question is a bit too localised for the site. \$\endgroup\$ Commented Jan 14, 2013 at 1:09

1 Answer 1


The Y offset you are computing should actually be applied to the Z axis:

gl.glTranslatef(xPath, 0f, yPath - 30f);

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