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    <p>With regards to your "how to do it wrong", I hate to break it to you, but it's not wrong; rather, it's incomplete. You need to do those kinds of work independently of the parent child relationship.</p> <p>Here's an example of that: The wheel is attached to the car just like you mentioned. If you translate or rotate the car, you don't need to touch the wheels - they're in the same location <em>relative to the car</em>. However, when you try to get the wheel's new location in the 'real world', you have to traverse down the tree, applying the matrix transformations as you go. That all works, right?</p> <p>When you rotate an object, it rotates around its OWN origin. So a wheel should probably be rotating around its y axis, and a planet around its z axis. But now if you need to move a planet "around the sun", you're doing something completely different. This has to be calculated separately. That's not to say it's not going to be eased by using some of the same match you already have, (although I can't say for sure without doing the math myself) but it's entirely different. </p> <p>You're looking at actually changing the state of the object. That's the beauty of the scene graph! If you didn't have a scene graph, you would have to figure out all the various values all the way back to the main scene and then do all kinds of math. Here, you just have to do a little bit of trig and algebra to move around the planet (you can google the celestial mechanics) and move the planet relative to its star. The next time the main scene asks where the planet is, it will just go down the scene graph! :-D</p>
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    1. COI pick this as the best answer. My original approach was correct and I now do not know why I considered it to be wrong (too simple? :D) You are also right about the planetary rotation: I now included an additional node which handles the rotation around the sun. Thank you very much!
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    2. COIf the sun rotates the planets will rotate aswell with this matrix algebra. Forward kinematics..
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    3. CO@Stefan then obviously the sun should simply be a child of the solar system as the planet is, and centered at the origin.
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