Very Simple Question, Earth Simulation

[stellar]

basically im tring to create a simple earth/sun simulation. The basic setup I have an animation for earth ( a sphere ) where rotateY moves from 0 to 360 in 24 frames ( each frame represents an hour ). I then grouped the earth to create a parent transform and set the rotateX to 23, to give earth its axis tilt. finally, i just need to orbit the earth ( yet another parent transform ) about the sun, but the axis remains locked towards the sun. meaning when the earth starts its orbit, its north axis points twards the sun, and when the earth is half way around in orbit, it's axis still points twards the sun, however it should point away.
I need someway of keeping earths axis transform locked in the same direction, throughout its orbit? can anyone assist?

Basic layout

CODE
Orbit Transform ( RotateY from 0 ... 360, pivot at world origin )
     Earth Tilt Transform ( RotateX = 23 )
          Earth ( RotateY from 0 ... 360, pivot at mesh center )

Thanks!
-Velik

[ptb]

Parent a locator to the sun instead of the earth and then point constraint the earth to the locator.

[uiron]

you mean, you want this effect?

you need to keep earth rotation separate from "rotate around the sun" rotation space, which is simple, you need to constrain just earth MOTION around the sun.

• put first locator at sun's pivot. this will be used to animate earth rotation around the sun
• put second locator at earth's pivot; parent constrain it to the first locator; this will calculate earth position as you animate first locator
• POINT constrain earth to the second locator; if you animate first one now, you can see that earth is translated around the sun, but not rotated;
• tilt earth along X axis. try animating again, you can see that X tilt remains the same, not relative to rotation around the sun;
• if you're animating earth Y rotation to simulate day/night animation, you will need to change earth's euler rotation order to YXZ

that's it.