When you transform a parent, its children are transformed with it. This lets you, for example, model a leg by making the thigh the child of the hip, the knee the child of the thigh, the shin the child of the knee, the foot the child of the shin, and so on. Rotating one join rotates the rest of the leg under that joint.
Though the moon is the child of the planet, you can also give the moon motion that’s independent of the planet. For example, you can make it orbit the planet. If you later change the orbiting motion of the planet, the moon continues to follow the planet’s motion, but stills retains its original orbiting motion.
To control multiple objects with one node, you can group objects together under a new transform node. By grouping objects, you can move, shade, texture, and do many other actions to all the objects at the same time.
Except where otherwise noted, this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License