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Vizard 8 » Tutorials & Examples » 3D models » Coordinate Systems » Tutorial: Node Parents

8.1

Tutorial Node Parents

Key Concepts

• A node's place in the scene graph can be changed at any time with the <node3d>.setParent() method.
• By default, the <node3d>.setPosition() method works in the node parent's coordinate system.

Explanation

Now we add two smaller pigeons we will move about using different coordinate systems.  To distinguish between them, we'll give them some labels:

The setPosition method changes the transformation matrix associated with a node. We now modify the transformation matrices of both pigeons so that they move back 1 meter on their parent's z axis.  If the pigeons had the same parents, they would be overlapping each other, but we set the parent of childPigeon to mamaPigeon. This moves childPigeon 1 meter behind mamaPigeon. The worldPigeon however is anchored in the world's coordinate system and is positioned 1 meter behind the world origin. Their positions in the world are different because the positions of their parents are different:  

Run the script to see where each pigeon is located.

Hit the spacebar to again animate mamaPigeon walking. You'll see that childPigeon also moves, staying a constant 1 meter behind her. The child's actions looks a bit unnatural, especially when the mother rotates, but this demonstrates how a parent's movements will affect it's children.