# FreeGLUT - Making Planets Orbit at their own Speed

I'm currently working on a project for Uni using FreeGLUT to make a simple solar system simulation. I've got to the point where I've implemented all the planets and have used a Scene Graph to link them all together. The issue I'm having with now though is basically the planets and moons orbit correctly at their own orbit speeds.

I'm not really experienced with using matrices for stuff like this so It's likely why I can't figure out how exactly to get it working. This is where I'm applying the transformation matrices, as well as pushing and popping them. This is within the Render function that every planet including the sun and moons will have and run.

if (tag != "Sun")
{
glRotatef(orbitAngle, orbitRotation.X, orbitRotation.Y, orbitRotation.Z);
}

glPushMatrix();

glTranslatef(position.X, position.Y, position.Z);
glRotatef(rotationAngle, rotation.X, rotation.Y, rotation.Z);
glScalef(scale.X, scale.Y, scale.Z);

glDrawElements(GL_TRIANGLES, mesh->indiceCount, GL_UNSIGNED_SHORT, mesh->indices);

if (tag != "Sun")
{
glPopMatrix();
}


The "If(tag != "Sun") parts are my attempts are getting the planets to orbit correctly though it likely isn't the way I'm meant to be doing it. So I was wondering if someone would be able to help me? As I really don't have an idea on what I would do to get it working. Using the if statement is truthfully the closest I've got to it working but there are still weird effects like the planets orbiting faster then they should depending on the number of planets actually be updated/rendered.