A small orrery in OpenGL

In this assignment you should use OpenGL to animate the movement of the Earth and Moon around the Sun. To increase the level of realism you should use light and use textures for the Earth and Moon. Your code should behave something like my example: ~thomas/VIS/OpenGL/orrery . If you are using KDE and not Gnome, you need to hit the return key, with the mouse in the window, to start the animation (it seems).

Note the following:

• You can increase the speed of the rotation by pressing + (several times) and decrease it by typing - (with the mouse in the OpenGL-window).
• There is a menu with three alternatives (Full light, Darkness, Quit). Try it!
• Using textures is not compulsory. If you do not use textures, the Sun, Earth and Moon should have different colours (and your program should still use light).
  

The physics does not have to be correct, but your program should do the following (to force you to learn OpenGL):

• Take the tilt of the Earth axis into account. The tilt is approximately 23.4°.
• Assume that the Earth makes a complete revolution around its on axis in one time unit (corresponds to a day), and around the Sun in 365 time units. Assume that the Moon needs 30 time units to go around the Earth. Make sure that the Earth rotates in the correct direction.
  
• You may assume that both the Earth and the Moon travel in circular paths and in the same plane.
• The Moon keeps the same face turned to the Earth at all times due to the tides (tidal locking). Make sure your program shows the correct side.
  
• The relative sizes of Earth and Moon do not have to be correct, but if you want to use it, the quotient between the diameters is roughly 3.7. You may assume that the bodies have a spherical shape. Do not forget to set the normals and the texture coordinates. Note that glutSolidSphere does not set texture coordinates.
• To make the textures look nice (to avoid flicker) you need to build mipmaps (gluBuild2DMipmaps). Also set the GL_TEXTURE_MIN_FILTER to GL_LINEAR_MIPMAP_NEAREST (which I thought looked best).
  
• There should be some stars (but they do not have to correspond to real constellations).
• When one has chosen Darkness from the menu, the light should appear to come from the Sun.
• The spheres should not deform if we change the proportions of the window.
• Your program does not have to consider shadows.
  
• For more data you can use Wikipedia, Earth, Moon.
  

Under ~thomas/VIS/OpenGL you find two textures, earth.ppm and moon.ppm that you can use. The images have the same format, width = 640 and height = 320. The files consist of a four line header followed by 204800 (=  640 x 320) rows with an RGB-triple per row. The files are in human readable form, so you can inspect them. To see the image you can use xv, for example. Type xv earth.ppm .

These textures were produced by projecting the surface of the bodies on a flat surface, so when we make the inverse transformation, the result should be reasonable (no major distortion). I fetched the textures several years ago (from NASA I think). If you would prefer a cloudy Earth, there are several such textures available on the web.