How to rotate a lightsource around a fixed object (OpenGL)?

I'm trying to make a light source rotate around my character model in my OpenGL project, but as I try it, all I got so far is my model rotating like crazy (or the floor).

My rendering code looks like this:

void mainRender() {
    updateState();
    renderScene();
    glFlush();
    glutPostRedisplay();

    //spin = (spin + 30) % 360;

    Sleep(30);
}

void renderScene() {
    glClearColor(backgrundColor[0],backgrundColor[1],backgrundColor[2],backgrundColor[3]);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  // limpar o depth buffer

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    updateCam();
    renderFloor();
    modelAL.Translate(0.0f,1.0f,0.0f);
    modelAL.Draw();
}


void renderFloor() {


    // set things up to render the floor with the texture
    glShadeModel(GL_SMOOTH);
    glEnable(type);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

    glPushMatrix();

    glTranslatef(-(float)planeSize/2.0f, 0.0f, -(float)planeSize/2.0f);

    float textureScaleX = 10.0;
    float textureScaleY = 10.0;
    glColor4f(1.0f,1.0f,1.0f,1.0f);
    int xQuads = 40;
    int zQuads = 40;
    for (int i = 0; i < xQuads; i++) {
        for (int j = 0; j < zQuads; j++) {
            glBegin(GL_QUADS);
                glTexCoord2f(1.0f, 0.0f);   // coords for the texture
                glNormal3f(0.0f,1.0f,0.0f);
                glVertex3f(i * (float)planeSize/xQuads, 0.0f, (j+1) * (float)planeSize/zQuads);

                glTexCoord2f(0.0f, 0.0f);  // coords for the texture
                glNormal3f(0.0f,1.0f,0.0f);
                glVertex3f((i+1) * (float)planeSize/xQuads, 0.0f, (j+1) * (float)planeSize/zQuads);

                glTexCoord2f(0.0f, 1.0f);  // coords for the texture
                glNormal3f(0.0f,1.0f,0.0f);
                glVertex3f((i+1) * (float)planeSize/xQuads, 0.0f, j * (float)planeSize/zQuads);

                glTexCoord2f(1.0f, 1.0f);  // coords for the texture
                glNormal3f(0.0f,1.0f,0.0f);
                glVertex3f(i * (float)planeSize/xQuads, 0.0f, j * (float)planeSize/zQuads);

            glEnd();
        }
    }

    glDisable(type);


    glPopMatrix();
}

How could I make this new lightsource rotate around my "modelAL" object?

---

For the fixed pipeline, light source position assigned with glLight() are transformed with the model-view matrix, just as normal objects are. So you can use the transformation functions to position and rotate your light source as you would normal objects.

To rotate a light source (or other object) around a point, you need to follow these steps. Let L be where the light source will be when the rotation is 0 degrees, and O be the subject - the object around which you want to rotate the light source.

Position the light source at LO (the position of the light source relative to the subject)

Rotate it about the required axis (probably the Y axis)

Translate it by O to move it into position.

Because of the way OpenGL works, you essentially do these in backwards order. Basically it would go like this:

glPushMatrix();
glTranslatef(O.x,O.y,O.z);
glRotate(angle,0,1,0);
GLfloat lightpos[4] = {L.x-O.x,L.y-O.y,L.z-O.z,1};
glLightfv(GL_LIGHT0,GL_POSITION,lightpos);
glPopMatrix();

Note, this only applies to positioned light sources, not directional ones ie with w=0.

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